Caffeine is a naturally occurring stimulant found in various plants, including coffee beans, tea leaves, cacao pods, and kola nuts. It is the world's most widely consumed psychoactive substance and is commonly ingested through coffee, tea, soft drinks, energy drinks, and certain medications. The primary role of caffeine is to stimulate the central nervous system, helping to reduce fatigue, improve concentration, and increase alertness.

Chemically, caffeine belongs to a class of compounds known as xanthines. Its molecular structure consists of a purine base, similar to that found in adenine and guanine, which are essential components of DNA and RNA. This structural similarity allows caffeine to interact with various biological systems, particularly those involving neurotransmitters like adenosine.

Adenosine is a neurotransmitter that promotes sleep and relaxation by binding to its specific receptors in the brain. Caffeine works by blocking these adenosine receptors, thereby preventing the onset of drowsiness and making you feel more awake. This blockade leads to a cascade of other neurotransmitter releases, such as dopamine and norepinephrine, which further contribute to its stimulating effects.

In addition to its well-known impact on alertness and wakefulness, caffeine has been studied for its potential benefits in various health conditions. Research has shown that caffeine can improve athletic performance, enhance cognitive function, and may even offer protective benefits against certain neurological diseases like Parkinson's and Alzheimer's. However, these benefits can vary based on individual tolerance, dosage, and frequency of use.

Overall, caffeine is a multifaceted compound that plays a significant role in daily life for millions of people around the world. Its effects on the central nervous system make it a popular choice for combating fatigue and enhancing mental performance, but it should be consumed mindfully to avoid potential side effects.

Caffeine is primarily used to combat fatigue, enhance alertness, and improve mental focus. Its stimulating effects on the central nervous system make it a go-to choice for individuals needing a mental or physical boost, whether for work, study, or athletic performance. Beyond its everyday use, caffeine has been extensively studied for its potential benefits in various domains, including cognitive function, physical performance, and even certain health conditions.

One of the most well-documented uses of caffeine is its ability to improve cognitive function. Studies have shown that caffeine can enhance various aspects of mental performance, such as attention, reaction time, and memory. For instance, a review published in the journal "Psychopharmacology" found that caffeine reliably improves vigilance and attention, particularly in situations where individuals are sleep-deprived or experiencing mental fatigue. This makes caffeine a popular choice for students, professionals, and anyone needing to maintain high levels of cognitive function over extended periods.

Caffeine is also widely used in the realm of physical performance. Numerous studies have demonstrated its efficacy in enhancing endurance and strength during exercise. A study published in the "Journal of Applied Physiology" found that caffeine ingestion significantly improved time to exhaustion and power output in athletes. This is attributed to caffeine's ability to increase adrenaline levels, mobilize fatty acids from fat tissues, and enhance muscle contractility. These effects make caffeine a common ingredient in pre-workout supplements and energy drinks aimed at athletes and fitness enthusiasts.

In addition to its cognitive and physical performance benefits, caffeine has been investigated for its potential protective effects against certain diseases. Research has suggested that regular caffeine consumption may be associated with a reduced risk of developing neurodegenerative diseases like Parkinson's and Alzheimer's. A study published in the "Journal of Alzheimer's Disease" found that caffeine intake was linked to a lower incidence of these conditions, possibly due to its neuroprotective properties and ability to reduce inflammation.

However, it's important to note that the effects of caffeine can vary widely among individuals, influenced by factors such as genetic predisposition, tolerance, and overall health. While moderate caffeine consumption is generally considered safe and beneficial, excessive intake can lead to side effects such as anxiety, insomnia, and gastrointestinal issues.

In conclusion, caffeine is a versatile compound used for enhancing cognitive function, improving physical performance, and potentially offering protective benefits against certain diseases. The body of research supports its efficacy in these areas, but it's crucial to consume caffeine in moderation to avoid adverse effects.

Caffeine exerts its effects primarily through its action on the central nervous system. The fundamental mechanism by which caffeine works involves the blockade of adenosine receptors in the brain. Adenosine is a neurotransmitter that promotes sleep and relaxation by binding to its receptors and slowing down neural activity. By blocking these receptors, caffeine prevents adenosine from exerting its calming effects, leading to increased alertness and wakefulness.

When adenosine receptors are blocked, several downstream effects occur. One of the most significant is the increase in the release of other neurotransmitters, such as dopamine and norepinephrine. Dopamine is involved in reward and pleasure pathways, while norepinephrine is associated with the fight-or-flight response, increasing heart rate and blood flow to muscles. This surge in neurotransmitter activity enhances mood, improves focus, and prepares the body for physical exertion.

Apart from its action on adenosine receptors, caffeine also influences the levels of cyclic adenosine monophosphate (cAMP) in cells. By inhibiting the enzyme phosphodiesterase, which breaks down cAMP, caffeine leads to an accumulation of this molecule. Elevated cAMP levels activate protein kinase A (PKA) and other signaling pathways that increase energy production, enhance lipolysis (fat breakdown), and improve muscle contractility. This biochemical cascade contributes to caffeine's ability to enhance physical performance and endurance.

Interestingly, caffeine's effects are not limited to the central nervous system. It also impacts the peripheral nervous system and various organs. For example, caffeine stimulates the release of adrenaline from the adrenal glands, which amplifies the body's readiness for action. This is why caffeine can increase heart rate, elevate blood pressure, and redirect blood flow to muscles, all of which are beneficial during physical activities.

Caffeine's influence on the brain also extends to cognitive functions. It has been shown to improve reaction time, vigilance, and attention, particularly in sleep-deprived individuals. The enhanced dopamine signaling associated with caffeine intake can also boost mood and reduce the perception of effort during physical tasks, making strenuous activities feel less taxing.

In summary, caffeine's multifaceted effects stem from its ability to block adenosine receptors, increase neurotransmitter release, and elevate cAMP levels. These actions collectively enhance alertness, cognitive function, and physical performance, making caffeine a popular and effective stimulant. However, it's essential to consume caffeine mindfully, as excessive intake can lead to undesirable side effects and diminished benefits.

Caffeine's effects can vary between men and women due to physiological differences, hormonal fluctuations, and metabolic factors. While both sexes can benefit from caffeine's stimulating properties, there are specific considerations and applications in men's and women's health that merit attention.

For men, caffeine is often used to enhance physical performance and muscle strength. Studies have demonstrated that caffeine can significantly improve endurance, power output, and overall athletic performance in men. This is partly due to caffeine's ability to increase adrenaline levels, which enhances muscle contractility and energy availability. Additionally, research published in the "European Journal of Applied Physiology" suggests that caffeine may also increase testosterone levels during exercise, potentially providing an additional performance boost. Men who engage in resistance training or endurance sports may find caffeine particularly beneficial for optimizing their workout results.

In women's health, caffeine's use is more nuanced, especially considering hormonal fluctuations related to the menstrual cycle, pregnancy, and menopause. For instance, during the menstrual cycle, women may experience variations in caffeine sensitivity due to changes in hormone levels. A study published in "Pharmacology Biochemistry and Behavior" found that caffeine metabolism can be slower during the luteal phase of the menstrual cycle, potentially leading to prolonged effects and increased sensitivity. Women may need to adjust their caffeine intake based on these cyclical changes to avoid side effects like jitteriness or insomnia.

Pregnancy is another critical period where caffeine consumption needs careful consideration. High caffeine intake during pregnancy has been associated with an increased risk of miscarriage, preterm birth, and low birth weight. The American College of Obstetricians and Gynecologists recommends that pregnant women limit their caffeine intake to no more than 200 mg per day (approximately one 12-ounce cup of coffee). This cautious approach helps minimize potential risks while still allowing for moderate caffeine consumption.

For women experiencing menopause, caffeine's impact on symptoms such as hot flashes and sleep disturbances can be significant. Some studies suggest that caffeine may exacerbate hot flashes and disrupt sleep, making it essential for menopausal women to monitor their intake and adjust accordingly. However, caffeine can also provide benefits, such as improved mood and cognitive function, which can be particularly valuable during this life stage.

In addition to these specific considerations, both men and women should be aware of individual tolerance levels and potential side effects. Factors such as body weight, genetic predisposition, and overall health can influence how caffeine affects each person. It's essential to listen to your body and adjust caffeine intake based on personal experience and health goals.

In summary, while caffeine provides numerous benefits for both men and women, its use should be tailored to account for physiological differences, hormonal fluctuations, and life stages. By understanding these factors, individuals can optimize their caffeine consumption to enhance physical performance, cognitive function, and overall well-being.

The optimal amount of caffeine varies widely among individuals based on factors such as age, body weight, tolerance, and sensitivity. Generally, moderate caffeine consumption is considered safe and beneficial for most people. The U.S. Food and Drug Administration (FDA) suggests that up to 400 milligrams (mg) of caffeine per day—approximately the amount in four 8-ounce cups of coffee—is a safe limit for most healthy adults. This amount can help improve alertness, concentration, and physical performance without causing significant side effects.

For those new to caffeine or with a low tolerance, starting with smaller doses is advisable. Beginning with 50 to 100 mg, which is roughly equivalent to one cup of tea or a small soda, can help gauge individual sensitivity. From there, you can gradually increase your intake to find the optimal amount that provides the desired effects without causing jitteriness, anxiety, or sleep disturbances.

Athletes and individuals engaging in high-intensity physical activities might benefit from slightly higher doses of caffeine. Research published in the "Journal of Applied Physiology" suggests that doses ranging from 3 to 6 mg per kilogram (kg) of body weight can enhance endurance and strength performance. For example, a 70-kg (154-pound) individual might consume between 210 and 420 mg of caffeine before exercise to optimize their performance. However, it's essential to experiment with timing and dosage during training sessions to avoid adverse effects during competition.

Special populations, such as pregnant women, should exercise caution with caffeine intake. The American College of Obstetricians and Gynecologists recommends limiting caffeine consumption to no more than 200 mg per day during pregnancy to minimize potential risks, such as miscarriage and low birth weight. Similarly, individuals with certain medical conditions, such as anxiety disorders, hypertension, or heart issues, should consult with a healthcare provider before consuming caffeine, as it may exacerbate symptoms.

Children and adolescents are generally more sensitive to caffeine, and their intake should be limited. The American Academy of Pediatrics advises that children under 12 should avoid caffeine, while adolescents aged 12 to 18 should limit their intake to no more than 100 mg per day, equivalent to one 8-ounce cup of coffee or two cans of soda.

In summary, the ideal amount of caffeine varies based on individual factors and specific needs. For most healthy adults, up to 400 mg per day is safe and effective for enhancing alertness and performance. Special populations, such as pregnant women, children, and individuals with certain medical conditions, should adhere to more stringent guidelines and consult healthcare providers for personalized recommendations. By adjusting caffeine intake to suit individual circumstances, you can maximize its benefits while minimizing potential risks.

While caffeine is widely consumed and generally considered safe for most people, it can cause a range of side effects, particularly when consumed in high doses or by individuals with certain sensitivities. Understanding these potential side effects can help you make informed decisions about your caffeine consumption.

One of the most common side effects of caffeine is insomnia or disrupted sleep. Caffeine stimulates the central nervous system and can interfere with the natural sleep-wake cycle by blocking adenosine receptors, which promote sleep. This can lead to difficulty falling asleep, frequent awakenings during the night, and reduced sleep quality. The half-life of caffeine is approximately 5 to 6 hours, meaning it can stay in your system for an extended period. To minimize sleep disturbances, it's advisable to limit caffeine intake in the late afternoon and evening.

Another frequent side effect is increased anxiety and jitteriness. Caffeine can raise levels of stress hormones like adrenaline, which can lead to feelings of nervousness, restlessness, and anxiety. This effect is more pronounced in individuals who are sensitive to caffeine or consume it in large quantities. If you experience these symptoms, reducing your caffeine intake or opting for lower-caffeine beverages like tea may help.

Gastrointestinal issues are also a potential side effect of caffeine consumption. Caffeine can stimulate the production of stomach acid, which may lead to symptoms like acid reflux, heartburn, or an upset stomach. In some individuals, caffeine acts as a mild laxative, increasing the frequency of bowel movements. If you have a sensitive stomach or a condition like gastroesophageal reflux disease (GERD), it may be beneficial to moderate your caffeine intake and monitor how your body responds.

Caffeine can also cause cardiovascular effects, such as increased heart rate and elevated blood pressure. While these effects are generally mild for most people, they can be more significant in individuals with pre-existing heart conditions or hypertension. A study published in the "American Journal of Hypertension" found that caffeine can cause a temporary increase in blood pressure, particularly in those who are not regular consumers. If you have cardiovascular concerns, it's important to discuss your caffeine consumption with a healthcare provider.

Dependency and withdrawal symptoms are additional considerations. Regular consumption of caffeine can lead to physical dependence, and sudden cessation may result in withdrawal symptoms such as headaches, fatigue, irritability, and difficulty concentrating. These symptoms typically appear within 12 to 24 hours of stopping caffeine intake and can last for a few days. Gradually reducing caffeine consumption can help mitigate withdrawal effects.

In summary, while caffeine offers numerous benefits, it can also cause side effects such as insomnia, anxiety, gastrointestinal issues, cardiovascular effects, and withdrawal symptoms. These effects can vary based on individual sensitivity, dosage, and frequency of consumption. By being mindful of your caffeine intake and paying attention to how your body responds, you can enjoy the benefits of caffeine while minimizing potential adverse effects.

While caffeine is generally safe for most people when consumed in moderate amounts, certain individuals should exercise caution or avoid caffeine altogether due to potential health risks and adverse effects. Understanding these specific populations can help you make informed decisions about caffeine consumption.

Pregnant women are one group that should be cautious with caffeine intake. High doses of caffeine during pregnancy have been associated with increased risks of miscarriage, preterm birth, and low birth weight. The American College of Obstetricians and Gynecologists recommends that pregnant women limit their caffeine intake to no more than 200 mg per day, roughly equivalent to one 12-ounce cup of coffee. This guideline helps minimize potential risks while allowing for moderate consumption.

Individuals with cardiovascular conditions, such as hypertension or heart disease, should also be mindful of caffeine intake. Caffeine can cause a temporary increase in blood pressure and heart rate, which may exacerbate existing cardiovascular issues. A study published in the "American Journal of Hypertension" found that caffeine can elevate blood pressure, particularly in non-habitual consumers. If you have a history of high blood pressure or heart problems, it's essential to consult with a healthcare provider before consuming caffeine.

People with anxiety disorders or prone to panic attacks may find that caffeine exacerbates their symptoms. Caffeine stimulates the central nervous system and increases the release of stress hormones like adrenaline, which can lead to heightened feelings of anxiety, nervousness, and restlessness. If you experience anxiety or panic disorders, reducing or eliminating caffeine from your diet may help alleviate these symptoms.

Individuals with gastrointestinal issues, such as gastroesophageal reflux disease (GERD) or irritable bowel syndrome (IBS), may also need to avoid caffeine. Caffeine can stimulate the production of stomach acid, leading to symptoms like acid reflux, heartburn, and stomach upset. Additionally, it can act as a mild laxative, increasing bowel movement frequency, which can be problematic for those with IBS. Monitoring your body's response to caffeine and adjusting intake accordingly can help manage these symptoms.

Children and adolescents are generally more sensitive to caffeine, and their intake should be limited. The American Academy of Pediatrics advises that children under 12 should avoid caffeine, while adolescents aged 12 to 18 should limit their intake to no more than 100 mg per day, equivalent to one 8-ounce cup of coffee or two cans of soda. Excessive caffeine consumption in young individuals can interfere with sleep, contribute to anxiety, and impact overall development.

Lastly, individuals with certain medical conditions or those taking specific medications should consult with a healthcare provider before consuming caffeine. For example, people with sleep disorders, such as insomnia or sleep apnea, should avoid caffeine as it can disrupt sleep patterns. Additionally, caffeine can interact with medications like certain antibiotics, antidepressants, and heart medications, potentially leading to adverse effects.

In summary, while caffeine is safe for most people, certain populations should be cautious or avoid it altogether. Pregnant women, individuals with cardiovascular or anxiety disorders, those with gastrointestinal issues, children, adolescents, and people with specific medical conditions or medications should consult with healthcare providers to determine the appropriate level of caffeine intake. By understanding these considerations, you can make informed decisions about your caffeine consumption and minimize potential health risks.

Yes, caffeine supplements can interact with various medications, potentially altering their effects or increasing the risk of adverse reactions. Understanding these interactions is crucial for ensuring safety and efficacy when using caffeine supplements alongside other medications. Here are some notable interactions to be aware of:

1. Antibiotics: Certain antibiotics, such as ciprofloxacin and norfloxacin, can increase the levels of caffeine in the bloodstream. These antibiotics inhibit the enzyme CYP1A2, which is responsible for metabolizing caffeine in the liver. As a result, caffeine's effects may be prolonged, leading to symptoms such as jitteriness, increased heart rate, and insomnia. If you are taking these antibiotics, it may be advisable to reduce your caffeine intake.
2. Antidepressants: Caffeine can interact with certain antidepressants, particularly those in the class of selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac) and fluvoxamine (Luvox). These medications also inhibit the CYP1A2 enzyme, potentially increasing caffeine levels in the body. Additionally, combining caffeine with monoamine oxidase inhibitors (MAOIs) can lead to a dangerous spike in blood pressure. It's essential to consult with a healthcare provider before combining caffeine supplements with antidepressants to avoid potential adverse effects.
3. Anticoagulants and Antiplatelet Drugs: Caffeine can enhance the effects of blood-thinning medications like warfarin (Coumadin) and antiplatelet drugs such as aspirin and clopidogrel (Plavix). This interaction can increase the risk of bleeding and bruising. If you are on these medications, it's crucial to monitor your caffeine intake and discuss any concerns with your healthcare provider.
4. Asthma Medications: Theophylline, a medication used to treat asthma and other respiratory conditions, is chemically similar to caffeine. Both theophylline and caffeine are metabolized by the CYP1A2 enzyme, leading to potential competitive inhibition. Taking caffeine supplements alongside theophylline can result in increased theophylline levels, causing side effects such as nausea, vomiting, and heart palpitations. Consult your healthcare provider to adjust dosages if necessary.
5. Stimulant Medications: Combining caffeine with other stimulant medications, such as those used to treat attention deficit hyperactivity disorder (ADHD) like amphetamines (Adderall) or methylphenidate (Ritalin), can amplify stimulant effects. This can lead to increased heart rate, elevated blood pressure, anxiety, and difficulty sleeping. It's essential to manage caffeine intake and seek medical advice to avoid excessive stimulation.
6. Diabetes Medications: Caffeine can affect blood sugar levels and may interfere with the effectiveness of diabetes medications, such as insulin or oral hypoglycemic agents. For individuals managing diabetes, monitoring blood sugar levels and consulting with a healthcare provider about caffeine consumption is important to maintain optimal blood glucose control.
7. Heart Medications: Caffeine can interact with various heart medications, including beta-blockers like propranolol and metoprolol, potentially reducing their effectiveness. Additionally, caffeine can increase heart rate and blood pressure, counteracting the intended effects of these medications. If you are taking heart medications, it's advisable to discuss caffeine intake with your healthcare provider.

In summary, caffeine supplements can interact with a range of medications, potentially altering their effects or increasing the risk of adverse reactions. Antibiotics, antidepressants, anticoagulants, asthma medications, stimulants, diabetes medications, and heart medications are some of the drugs that may interact with caffeine. To ensure safety and efficacy, it's crucial to consult with a healthcare provider before combining caffeine supplements with any medications. By understanding these interactions, you can make informed decisions about your caffeine consumption and minimize potential health risks.

Caffeine is naturally present in a variety of foods and beverages and is also available in supplement form. The best sources of caffeine can vary depending on individual preferences, dietary restrictions, and specific health goals. Here are some of the most common and effective sources of caffeine:

1. Coffee: Coffee is perhaps the most popular and widely consumed source of caffeine. A typical 8-ounce cup of brewed coffee contains about 80 to 100 mg of caffeine, though this can vary depending on the type of coffee bean, brewing method, and serving size. Coffee also contains antioxidants and other beneficial compounds that may contribute to its health benefits, such as reduced risk of certain chronic diseases.
2. Tea: Tea is another excellent source of caffeine, and it comes in various types, including black, green, oolong, and white tea. Black tea generally has the highest caffeine content, with about 40 to 70 mg per 8-ounce cup, followed by green tea, which contains about 20 to 45 mg per cup. Tea also provides additional health benefits due to its high content of antioxidants, such as catechins and flavonoids.
3. Energy Drinks: Energy drinks are popular among individuals seeking a quick and convenient caffeine boost. These beverages typically contain between 70 and 300 mg of caffeine per serving, along with other ingredients like vitamins, amino acids, and herbal extracts. However, it's essential to consume energy drinks in moderation, as they can be high in sugar and other stimulants, which may lead to adverse effects when consumed in excess.
4. Soft Drinks: Many soft drinks, particularly colas, contain caffeine. A 12-ounce can of cola typically contains about 30 to 40 mg of caffeine. While these beverages can provide a moderate caffeine boost, they are often high in sugar and may not be the healthiest choice for regular consumption.
5. Chocolate and Cocoa Products: Caffeine is naturally present in cocoa beans, making chocolate and cocoa-based products a source of caffeine. Dark chocolate generally contains more caffeine than milk chocolate, with about 20 to 30 mg of caffeine per ounce. Cocoa powder and hot cocoa beverages also contain caffeine, with varying amounts depending on the product.
6. Caffeine Supplements: Caffeine is available in various supplement forms, including tablets, capsules, and powders. These products typically provide a standardized dose of caffeine, ranging from 100 to 200 mg per serving. Caffeine supplements can be a convenient and precise way to consume caffeine, particularly for individuals who want to control their intake or avoid the calories and other components found in caffeinated beverages.
7. Yerba Mate: Yerba mate is a traditional South American beverage made from the leaves of the Ilex paraguariensis plant. It contains about 30 to 50 mg of caffeine per 8-ounce cup and is also rich in antioxidants and other beneficial compounds. Yerba mate is enjoyed for its stimulating effects and unique flavor.
8. Guarana: Guarana is a plant native to the Amazon basin, and its seeds are a natural source of caffeine. Guarana extracts are often used in energy drinks, supplements, and weight loss products. The caffeine content in guarana can be quite high, with some extracts containing up to 6% caffeine by weight.

In summary, the best sources of caffeine include coffee, tea, energy drinks, soft drinks, chocolate, caffeine supplements, yerba mate, and guarana. Each source offers varying amounts of caffeine and additional health benefits or considerations. By understanding the different sources of caffeine, you can choose the one that best fits your lifestyle and health goals. Whether you prefer a warm cup of coffee, a refreshing tea, or a convenient supplement, there's a caffeine source to suit every preference.

Caffeine is available in a variety of forms, catering to different preferences, needs, and lifestyles. Whether you enjoy sipping on a hot beverage, need a quick energy boost, or prefer taking supplements, there's a form of caffeine to suit your requirements. Here are the most common forms of caffeine:

1. Beverages:
   • Coffee: Coffee is the most popular and widely consumed form of caffeine. It comes in various types, including brewed, instant, espresso, and cold brew. Each type has varying caffeine content, with brewed coffee generally containing 80 to 100 mg of caffeine per 8-ounce cup.
   • Tea: Tea is another common source of caffeine, available in several varieties such as black, green, oolong, and white tea. Black tea typically contains the most caffeine, with about 40 to 70 mg per 8-ounce cup, followed by green tea with 20 to 45 mg per cup.
   • Energy Drinks: Energy drinks are designed to provide a quick and convenient caffeine boost. They contain varying amounts of caffeine, ranging from 70 to 300 mg per serving, along with other ingredients like vitamins, amino acids, and herbal extracts.
   • Soft Drinks: Many soft drinks, especially colas, contain caffeine. A 12-ounce can of cola usually has about 30 to 40 mg of caffeine. While they can provide a moderate caffeine boost, they are often high in sugar and may not be the healthiest choice for regular consumption.
   • Yerba Mate: Yerba mate is a traditional South American beverage made from the leaves of the Ilex paraguariensis plant. It contains about 30 to 50 mg of caffeine per 8-ounce cup and is rich in antioxidants and other beneficial compounds.
2. Solid Foods:
   • Chocolate and Cocoa Products: Caffeine is naturally present in cocoa beans, making chocolate and cocoa-based products a source of caffeine. Dark chocolate generally contains more caffeine than milk chocolate, with about 20 to 30 mg of caffeine per ounce. Cocoa powder and hot cocoa beverages also contain caffeine, with varying amounts depending on the product.
   • Guarana: Guarana is a plant native to the Amazon basin, and its seeds are a natural source of caffeine. Guarana extracts are often used in energy bars, supplements, and weight loss products. The caffeine content in guarana can be quite high, with some extracts containing up to 6% caffeine by weight.
3. Supplements:
   • Caffeine Tablets and Capsules: Caffeine supplements are available in tablet and capsule forms, providing a standardized dose of caffeine, typically ranging from 100 to 200 mg per serving. These supplements offer a convenient and precise way to consume caffeine, particularly for individuals who want to control their intake or avoid the calories and other components found in caffeinated beverages.
   • Caffeine Powders: Caffeine powders are another supplement form, allowing for customizable dosing. However, caution is required when using caffeine powders, as it's easy to consume too much, leading to potential adverse effects.
   • Caffeine Chewing Gum: Caffeine gum provides a quick and convenient way to consume caffeine, with each piece typically containing 50 to 100 mg of caffeine. It offers a fast-acting energy boost, as caffeine is absorbed through the lining of the mouth.
4. Pharmaceutical Products:
   • Over-the-Counter Medications: Some over-the-counter medications, such as pain relievers, cold medicines, and alertness aids, contain caffeine. These medications often combine caffeine with other active ingredients to enhance their effectiveness. The caffeine content in these products can vary, so it's essential to read labels and follow dosing instructions.

In summary, caffeine comes in various forms, including beverages like coffee and tea, solid foods like chocolate and guarana, supplements like tablets, capsules, and powders, and pharmaceutical products. Each form offers different benefits and considerations, allowing you to choose the one that best fits your lifestyle and health goals. Whether you prefer a warm cup of coffee, a refreshing tea, a convenient supplement, or a quick-acting gum, there's a caffeine form to suit every preference.

Caffeine itself is the primary active compound responsible for its stimulating effects on the central nervous system. However, it is often found alongside other bioactive compounds, particularly in natural sources like coffee, tea, and cacao. These sub-compounds can enhance or modify the effects of caffeine, contributing to the overall experience and potential health benefits. Here are some of the key sub-compounds that play a role in the efficacy of caffeine:

1. Theobromine: Theobromine is a xanthine alkaloid found in cocoa beans, tea leaves, and some other plants. It is chemically related to caffeine and shares similar stimulant properties, though it is milder in its effects. Theobromine primarily acts as a vasodilator and smooth muscle relaxant, contributing to the cardiovascular benefits associated with cocoa and dark chocolate. In combination with caffeine, theobromine can enhance mood and cognitive function while providing a smoother, less jittery stimulation.
2. Theophylline: Theophylline is another xanthine alkaloid found in tea leaves and cocoa beans. It has bronchodilator properties, making it useful in the treatment of respiratory conditions like asthma. Theophylline also has stimulant effects on the central nervous system, similar to caffeine, but it is less potent. The presence of theophylline in tea can contribute to the overall stimulating effects and potential respiratory benefits of the beverage.
3. Catechins: Catechins are a type of flavonoid found in high concentrations in green tea. These antioxidants have been studied for their numerous health benefits, including anti-inflammatory, anti-carcinogenic, and cardiovascular protective effects. Catechins, particularly epigallocatechin gallate (EGCG), can enhance the metabolic effects of caffeine, promoting fat oxidation and weight management. The combination of catechins and caffeine in green tea makes it a powerful beverage for supporting overall health.
4. L-Theanine: L-Theanine is an amino acid found primarily in tea leaves, especially green tea. It is known for its calming effects, promoting relaxation without causing drowsiness. L-Theanine can modulate the stimulating effects of caffeine, reducing anxiety and jitteriness while enhancing focus and cognitive performance. The synergistic interaction between caffeine and L-Theanine is one reason why many people find green tea to be a smoother and more balanced source of caffeine compared to coffee.
5. Chlorogenic Acids: Chlorogenic acids are a group of polyphenol compounds found in coffee beans. They have antioxidant properties and may contribute to the potential health benefits of coffee, such as reduced risk of certain chronic diseases. Chlorogenic acids can also affect glucose metabolism, potentially enhancing the metabolic effects of caffeine. The presence of these compounds in coffee adds to its overall health-promoting properties.
6. Guaranine: Guaranine is the term used for the caffeine found in guarana seeds. While chemically identical to caffeine, guaranine is often combined with other compounds in guarana, such as tannins and saponins, which can slow the release of caffeine into the bloodstream. This slower release can provide a more sustained and gradual energy boost, with fewer crashes compared to other sources of caffeine.

In summary, while caffeine itself is the primary active compound responsible for its stimulating effects, several sub-compounds can enhance or modify its efficacy. Theobromine, theophylline, catechins, L-Theanine, chlorogenic acids, and guaranine are key compounds that contribute to the overall experience and potential health benefits of caffeine-containing products. Understanding the role of these sub-compounds can help you choose the best sources of caffeine to suit your needs and preferences.

Caffeine is known by several names, abbreviations, and chemical compounds, reflecting its widespread use and various sources. Here are some of the most common alternative names, misspellings, and related compounds:

1. Chemical Names and Abbreviations:
   • 1,3,7-Trimethylxanthine: This is the chemical name for caffeine, highlighting its structure as a xanthine derivative with three methyl groups.
   • C8H10N4O2: The molecular formula for caffeine, representing its composition of carbon, hydrogen, nitrogen, and oxygen atoms.
2. Common Names and Misspellings:
   • Caffiene: A frequent misspelling of caffeine.
   • Cafine: Another common misspelling.
   • Kaffeine: A less common misspelling, but occasionally seen.
3. Alternate Names and Synonyms:
   • Guaranine: The term used for caffeine derived from guarana seeds.
   • Mateine: The name for caffeine found in yerba mate, a traditional South American beverage.
   • Theine: An older term for caffeine when found in tea, though this term is less commonly used today.
4. Related Compounds and Ingredients:
   • Theobromine: A xanthine alkaloid similar to caffeine, found in cocoa beans and tea leaves, with milder stimulant properties.
   • Theophylline: Another xanthine alkaloid found in tea leaves and cocoa beans, known for its bronchodilator effects.
   • Methylxanthine: The class of compounds that includes caffeine, theobromine, and theophylline, all of which share a similar chemical structure.
5. Brand Names and Products:
   • NoDoz: A brand of over-the-counter caffeine tablets designed to increase alertness.
   • Vivarin: Another brand of caffeine tablets commonly used to combat drowsiness.
   • Caffeinated Beverages: Brand names like Red Bull, Monster, and Coca-Cola are well-known sources of caffeine in the form of energy drinks and soft drinks.
6. Herbal and Natural Sources:
   • Guarana: A plant native to the Amazon basin, whose seeds are rich in caffeine and often used in energy drinks and supplements.
   • Yerba Mate: A traditional South American beverage made from the leaves of the Ilex paraguariensis plant, containing caffeine, theobromine, and other beneficial compounds.
   • Kola Nut: The seed of the kola tree, used as a flavoring ingredient in cola beverages and a natural source of caffeine.

In summary, caffeine is known by various names, abbreviations, and related compounds, reflecting its diverse sources and widespread use. Whether referred to as 1,3,7-Trimethylxanthine, guaranine, theine, or simply caffeine, this stimulant is a common ingredient in many beverages, supplements, and medications. Understanding these alternative names and related compounds can help you recognize the presence of caffeine in different products and make informed decisions about your caffeine consumption.

When selecting a caffeine supplement, it's crucial to examine the product label to ensure quality, safety, and efficacy. Here are key factors to consider:

1. Caffeine Content and Dosage:
   • Amount per Serving: Look for the specific amount of caffeine provided per serving. This information is essential for managing your intake and avoiding excessive consumption. Most caffeine supplements provide between 100 to 200 mg per serving.
   • Serving Size: Ensure you understand the recommended serving size and how it correlates with the total caffeine content. This helps you accurately measure your intake.
2. Ingredient Transparency:
   • Active Ingredients: The label should clearly list all active ingredients, including the type and source of caffeine (e.g., caffeine anhydrous, guarana extract, green tea extract). Transparency about the source helps you understand the form of caffeine you're consuming.
   • Inactive Ingredients: Check for any additional inactive ingredients or fillers. While these are generally safe, it's important to know what else is included, especially if you have allergies or sensitivities.
3. Quality Certifications and Testing:
   • Third-Party Testing: Look for supplements that have been tested by independent third-party organizations. Certifications from groups like NSF International, Informed-Sport, or USP (United States Pharmacopeia) indicate that the product has been tested for purity, potency, and contaminants.
   • Good Manufacturing Practices (GMP): Ensure the product is manufactured in a facility that follows GMP guidelines. This certification ensures that the supplement is produced in a clean, controlled environment and meets quality standards.
4. Additional Ingredients:
   • Complementary Compounds: Some caffeine supplements include other ingredients designed to enhance the effects of caffeine or provide additional benefits. Common additives include L-Theanine (for reducing jitteriness and promoting relaxation), vitamins (like B vitamins for energy metabolism), and herbal extracts. Ensure these ingredients are listed and understand their purpose.
   • Potential Allergens: Check for any potential allergens, such as soy, gluten, or dairy, especially if you have known allergies or dietary restrictions.
5. Label Claims and Marketing:
   • Health Claims: Be cautious of exaggerated health claims. Legitimate supplements will provide clear, evidence-based benefits without making unrealistic promises.
   • Warnings and Precautions: A quality supplement label will include warnings and precautions about potential side effects, interactions with medications, and recommended use. This information is crucial for ensuring safe consumption.
6. Expiration Date:
   • Shelf Life: Verify the expiration date to ensure you are purchasing a fresh product. Using an expired supplement can reduce its effectiveness and potentially pose health risks.
7. Manufacturer Information:
   • Contact Details: The label should provide the manufacturer's contact information, including address and customer service number. This transparency allows you to reach out with any questions or concerns and indicates a reputable company.

In summary, when evaluating a caffeine supplement label, look for clear information on caffeine content and dosage, ingredient transparency, quality certifications, additional ingredients, and accurate health claims. Also, check for the expiration date and manufacturer information to ensure you're purchasing a high-quality, safe product. By paying attention to these details, you can make an informed decision and select a caffeine supplement that meets your needs and health goals.

The information provided on this website, including any text, images, or other material contained within, is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. This page was created by the SuppCo editiorial team, with AI summarization tools, including data from but not limited to following studies:

1. Bruno Ferreira Viana, G. Trajano, C. Ugrinowitsch, Flávio Oliveira Pires (2020). Caffeine increases motor output entropy and performance in 4 km cycling time trial. PLoS ONE, 15, . Link: 10.1371/journal.pone.0236592
2. Stephen C Lane, J. Areta, S. Bird, Vernon G. Coffey, L. Burke, B. Desbrow, L. Karagounis, J. Hawley (2013). Caffeine ingestion and cycling power output in a low or normal muscle glycogen state.. Medicine and science in sports and exercise, 45 8,
   1577-84 . Link: 10.1249/MSS.0b013e31828af183
3. M. Wilk, Aleksandra Filip, M. Krzysztofik, A. Maszczyk, A. Zając (2019). The Acute Effect of Various Doses of Caffeine on Power Output and Velocity during the Bench Press Exercise among Athletes Habitually Using Caffeine. Nutrients, 11, . Link: 10.3390/nu11071465
4. Aleksandra Filip-Stachnik, M. Krzysztofik, Magdalena Kaszuba, K. Leźnicka, Maciej Kostrzewa, J. Del Coso, M. Wilk (2021). Effects of Acute Caffeine Intake on Power Output and Movement Velocity During a Multiple-Set Bench Press Exercise Among Mild Caffeine Users. Journal of Human Kinetics, 78, 219 - 228. Link: 10.2478/hukin-2021-0044
5. J. Grgic, E. Trexler, Bruno Lazinica, Ž. Pedišić (2018). Effects of caffeine intake on muscle strength and power: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 15, . Link: 10.1186/s12970-018-0216-0
6. S. Jessen, Kasper Eibye, P. M. Christensen, M. Hostrup, J. Bangsbo (2021). No additive effect of acetaminophen when co-ingested with caffeine on cycling performance in well-trained young men.. Journal of applied physiology, , . Link: 10.1152/japplphysiol.00108.2021
7. M. Glaister, D. Muniz-Pumares, S. Patterson, P. Foley, G. McInnes (2015). Caffeine supplementation and peak anaerobic power output. European Journal of Sport Science, 15, 400 - 406. Link: 10.1080/17461391.2014.962619
8. M. Wilk, Aleksandra Filip, M. Krzysztofik, Mariola Gepfert, A. Zając, J. Del Coso (2020). Acute Caffeine Intake Enhances Mean Power Output and Bar Velocity during the Bench Press Throw in Athletes Habituated to Caffeine. Nutrients, 12, . Link: 10.3390/nu12020406
9. J. Williams, J. F. Signorile, W. Barnes, T. Henrich (1988). Caffeine, maximal power output and fatigue.. British Journal of Sports Medicine, 22, 132 - 134. Link: 10.1136/bjsm.22.4.132
10. M. Doherty, Paul D. Smith, M. Hughes, R. R. Davison (2004). Caffeine lowers perceptual response and increases power output during high-intensity cycling. Journal of Sports Sciences, 22, 637 - 643. Link: 10.1080/02640410310001655741
11. D. Robertson, J. Frölich, R. K. Carr, J. Watson, J. Hollifield, D. Shand, J. Oates (1978). Effects of caffeine on plasma renin activity, catecholamines and blood pressure.. The New England journal of medicine, 298 4,
    181-6 . Link: 10.1056/NEJM197801262980403
12. Kwasi Debrah, Rob Haigh, Robert S. Sherwin, June Murphy, David Kerr (1995). Effect of acute and chronic caffeine use on the cerebrovascular, cardiovascular and hormonal responses to orthostasis in healthy volunteers.. Clinical science, 89 5,
    475-80 . Link: 10.1042/CS0890475
13. J. D. Lane, C. Pieper, B. Phillips-bute, J. E. Bryant, C. Kuhn (2002). Caffeine Affects Cardiovascular and Neuroendocrine Activation at Work and Home. Psychosomatic Medicine, 64, 595-603. Link: 10.1097/01.PSY.0000021946.90613.DB
14. P. Tauler, Sonia Martínez, Carlos Moreno, M. Monjo, P. Martínez, A. Aguiló (2013). Effects of caffeine on the inflammatory response induced by a 15-km run competition.. Medicine and science in sports and exercise, 45 7,
    1269-76 . Link: 10.1249/MSS.0b013e3182857c8a
15. C. Papadelis, C. Kourtidou-Papadeli, E. Vlachogiannis, P. Skepastianos, Panayiotis Bamidis, N. Maglaveras, K. Pappas (2003). Effects of mental workload and caffeine on catecholamines and blood pressure compared to performance variations. Brain and Cognition, 51, 143-154. Link: 10.1016/S0278-2626(02)00530-4
16. Kwasi Debrah, June Murphy, David Kerr, R. Sherwin (1996). Effect of caffeine on recognition of and physiological responses to hypoglycaemia in insulin-dependent diabetes. The Lancet, 347, 19-24. Link: 10.1016/S0140-6736(96)91557-3
17. A. Imam-Fulani, B. Owoyele (2022). Effect Of Caffeine and Adrenaline on Memory and Anxiety in Male Wistar Rats.. Nigerian journal of physiological sciences : official publication of the Physiological Society of Nigeria, 37 1,
    69-76 . Link: 10.54548/njps.v37i1.9
18. D. Battram, T. Graham, F. Dela (2007). Caffeine's impairment of insulin‐mediated glucose disposal cannot be solely attributed to adrenaline in humans. The Journal of Physiology, 583, . Link: 10.1113/jphysiol.2007.130526
19. D. Battram, T. Graham, E. Richter, F. Dela (2005). The effect of caffeine on glucose kinetics in humans – influence of adrenaline. The Journal of Physiology, 569, . Link: 10.1113/jphysiol.2005.097444
20. Lluis Rodas, Sonia Martínez, A. Aguiló, P. Tauler (2020). Caffeine supplementation induces higher IL-6 and IL-10 plasma levels in response to a treadmill exercise test. Journal of the International Society of Sports Nutrition, 17, . Link: 10.1186/s12970-020-00375-4
21. D. Collado-Mateo, Ana Myriam Lavín-Pérez, E. Merellano-Navarro, J. Coso (2020). Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis. Nutrients, 12, . Link: 10.3390/nu12123603
22. Laurent Green, J. Green, P. Wickwire, J. McLester, Shawn C. Gendle, G. Hudson, R. Pritchett, C. Laurent (2007). Effects of caffeine on repetitions to failure and ratings of perceived exertion during resistance training.. International journal of sports physiology and performance, 2 3,
    250-9 . Link: 10.1123/IJSPP.2.3.250
23. J. Grgic, Ivana Grgić, C. Pickering, B. Schoenfeld, D. Bishop, Ž. Pedišić (2019). Wake up and smell the coffee: caffeine supplementation and exercise performance—an umbrella review of 21 published meta-analyses. British Journal of Sports Medicine, 54, 681 - 688. Link: 10.1136/bjsports-2018-100278
24. K. Woolf, Wendy K. Bidwell, Amanda G. Carlson (2009). Effect of Caffeine as an Ergogenic Aid During Anaerobic Exercise Performance in Caffeine Naïve Collegiate Football Players. Journal of Strength and Conditioning Research, 23, 1363-1369. Link: 10.1519/JSC.0b013e3181b3393b
25. D. Bell, I. Jacobs, Kristina Ellerington (2001). Effect of caffeine and ephedrine ingestion on anaerobic exercise performance.. Medicine and science in sports and exercise, 33 8,
    1399-403 . Link: 10.1097/00005768-200108000-00024
26. B. Lara, Jorge Gutiérrez-Hellín, Alberto García-Bataller, Paloma Rodríguez-Fernández, B. Romero-Moraleda, J. Del Coso (2019). Ergogenic effects of caffeine on peak aerobic cycling power during the menstrual cycle. European Journal of Nutrition, 59, 2525 - 2534. Link: 10.1007/s00394-019-02100-7
27. Ziyu Wang, Bopeng Qiu, Jie Gao, J. Del Coso (2022). Effects of Caffeine Intake on Endurance Running Performance and Time to Exhaustion: A Systematic Review and Meta-Analysis. Nutrients, 15, . Link: 10.3390/nu15010148
28. J. Grgic (2018). Caffeine ingestion enhances Wingate performance: a meta-analysis. European Journal of Sport Science, 18, 219 - 225. Link: 10.1080/17461391.2017.1394371
29. B. Lara, J. Salinero, Verónica Giráldez-Costas, J. Del Coso (2021). Similar ergogenic effect of caffeine on anaerobic performance in men and women athletes. European Journal of Nutrition, 60, 4107 - 4114. Link: 10.1007/s00394-021-02510-6
30. K. Woolf, Wendy K. Bidwell, Amanda G. Carlson (2008). The effect of caffeine as an ergogenic aid in anaerobic exercise.. International journal of sport nutrition and exercise metabolism, 18 4,
    412-29 . Link: 10.1123/IJSNEM.18.4.412
31. W. Miyagi, R. Bertuzzi, F. Nakamura, R. A. D. de Poli, A. Zagatto (2018). Effects of Caffeine Ingestion on Anaerobic Capacity in a Single Supramaximal Cycling Test. Frontiers in Nutrition, 5, . Link: 10.3389/fnut.2018.00086
32. R. Silveira, Victor A. Andrade-Souza, Lucyana Arcoverde, F. Tomazini, André Sansônio, D. Bishop, R. Bertuzzi, A. Lima-Silva (2018). Caffeine Increases Work Done above Critical Power, but Not Anaerobic Work. Medicine & Science in Sports & Exercise, 50, 131–140. Link: 10.1249/MSS.0000000000001408
33. K. Collomp, S. Ahmaidi, M. Audran, Chanal Jl, C. Prefaut (1991). Effects of caffeine ingestion on performance and anaerobic metabolism during the Wingate Test.. International journal of sports medicine, 12 5,
    439-43 . Link: 10.1055/S-2007-1024710
34. Rodrigo A. B. de Poli, W. Miyagi, F. Nakamura, A. Zagatto (2016). Caffeine Improved Time to Exhaustion But Did Not Change Alternative Maximal Accumulated Oxygen Deficit Estimated During a Single Supramaximal Running Bout.. International journal of sport nutrition and exercise metabolism, 26 6,
    549-557 . Link: 10.1123/ijsnem.2016-0038
35. T. Beck, T. Housh, Richard Schmidt, G. Johnson, D. J. Housh, J. Coburn, M. Malek (2006). THE ACUTE EFFECTS OF A CAFFEINE‐CONTAINING SUPPLEMENT ON STRENGTH,MUSCULAR ENDURANCE, AND ANAEROBIC CAPABILITIES. Journal of Strength and Conditioning Research, 20, 506–510. Link: 10.1519/18285.1
36. M. Glaister, D. Muniz-Pumares, S. Patterson, P. Foley, G. McInnes (2015). Caffeine supplementation and peak anaerobic power output. European Journal of Sport Science, 15, 400 - 406. Link: 10.1080/17461391.2014.962619
37. Shahin Minaei, M. Jourkesh, R. Kreider, S. Forbes, Tácito P. Souza-Junior, S. McAnulty, D. Kalman (2021). CYP1A2 Genotype Polymorphism Influences the Effect of Caffeine on Anaerobic Performance in Trained Males.. International journal of sport nutrition and exercise metabolism, ,
    1-6 . Link: 10.1123/ijsnem.2021-0090
38. D. Bell, I. Jacobs, Kristina Ellerington (2001). Effect of caffeine and ephedrine ingestion on anaerobic exercise performance.. Medicine and science in sports and exercise, 33 8,
    1399-403 . Link: 10.1097/00005768-200108000-00024
39. Jon-Kyle Davis, J. Green (2009). Caffeine and Anaerobic Performance. Sports Medicine, 39, 813-832. Link: 10.2165/11317770-000000000-00000
40. Lucyana Arcoverde, R. Silveira, F. Tomazini, André Sansônio, R. Bertuzzi, A. Lima-Silva, Victor A. Andrade-Souza (2017). Effect of caffeine ingestion on anaerobic capacity quantified by different methods. PLoS ONE, 12, . Link: 10.1371/journal.pone.0179457
41. J. D. Lane, C. Barkauskas, R. Surwit, M. Feinglos (2004). Caffeine impairs glucose metabolism in type 2 diabetes.. Diabetes care, 27 8,
    2047-8 . Link: 10.2337/DIACARE.27.8.2047
42. T. Graham, P. Sathasivam, M. Rowland, Natasha Marko, F. Greer, D. Battram (2001). Caffeine ingestion elevates plasma insulin response in humans during an oral glucose tolerance test.. Canadian journal of physiology and pharmacology, 79 7,
    559-65 . Link: 10.1139/CJPP-79-7-559
43. Kwasi Debrah, June Murphy, David Kerr, R. Sherwin (1996). Effect of caffeine on recognition of and physiological responses to hypoglycaemia in insulin-dependent diabetes. The Lancet, 347, 19-24. Link: 10.1016/S0140-6736(96)91557-3
44. R. V. van Dam, W. Pasman, P. Verhoef (2004). Effects of coffee consumption on fasting blood glucose and insulin concentrations: randomized controlled trials in healthy volunteers.. Diabetes care, 27 12,
    2990-2 . Link: 10.2337/DIACARE.27.12.2990
45. Jason R Beam, A. Gibson, C. Kerksick, C. Conn, Ailish C. White, C. Mermier (2015). Effect of post-exercise caffeine and green coffee bean extract consumption on blood glucose and insulin concentrations.. Nutrition, 31 2,
    292-7 . Link: 10.1016/j.nut.2014.07.012
46. L. Moisey, S. Kacker, A. C. Bickerton, L. Robinson, T. Graham (2008). Caffeinated coffee consumption impairs blood glucose homeostasis in response to high and low glycemic index meals in healthy men.. The American journal of clinical nutrition, 87 5,
    1254-61 . Link: 10.1093/AJCN/87.5.1254
47. N. Whitehead, H. White (2013). Systematic review of randomised controlled trials of the effects of caffeine or caffeinated drinks on blood glucose concentrations and insulin sensitivity in people with diabetes mellitus.. Journal of human nutrition and dietetics : the official journal of the British Dietetic Association, 26 2,
    111-25 . Link: 10.1111/jhn.12033
48. A. Pizziol, V. Tikhonoff, C. D. Paleari, E. Russo, Alberto Mazza, G. Ginocchio, C. Onesto, L. Pavan, Edoardo Casiglia, A. Pessina (1998). Effects of caffeine on glucose tolerance: A placebo-controlled study. European Journal of Clinical Nutrition, 52, 846-849. Link: 10.1038/sj.ejcn.1600657
49. L. Robinson, Sonali Savani, D. Battram, D. McLaren, P. Sathasivam, T. Graham (2004). Caffeine ingestion before an oral glucose tolerance test impairs blood glucose management in men with type 2 diabetes.. The Journal of nutrition, 134 10,
    2528-33 . Link: 10.1093/JN/134.10.2528
50. Lisa Dewar, R. Heuberger (2017). The effect of acute caffeine intake on insulin sensitivity and glycemic control in people with diabetes.. Diabetes & metabolic syndrome, 11 Suppl 2,
    S631-S635 . Link: 10.1016/j.dsx.2017.04.017
51. K. Abbotts, T. Ewell, M. Bomar, H. Butterklee, J. Rebik, Christopher Bell (2022). Caffeine Augments the Lactate and Interleukin‐6 Response to Moderate‐Intensity Exercise in Men But Not Women. The FASEB Journal, 36, . Link: 10.1096/fasebj.2022.36.s1.r2033
52. K. Collomp, S. Ahmaidi, M. Audran, Chanal Jl, C. Prefaut (1991). Effects of caffeine ingestion on performance and anaerobic metabolism during the Wingate Test.. International journal of sports medicine, 12 5,
    439-43 . Link: 10.1055/S-2007-1024710
53. M. Glaister, B. Williams, D. Muniz-Pumares, C. Balsalobre-Fernández, P. Foley (2016). The Effects of Caffeine Supplementation on Physiological Responses to Submaximal Exercise in Endurance-Trained Men. PLoS ONE, 11, . Link: 10.1371/journal.pone.0161375
54. D. Souza, Michael Duncan, M. Polito (2019). Improvement of Lower-Body Resistance-Exercise Performance With Blood-Flow Restriction Following Acute Caffeine Intake.. International journal of sports physiology and performance, 14 2,
    216-221 . Link: 10.1123/ijspp.2018-0224
55. MahdaviReza, DaneghianSevana, JafariAfshar, HomayouniAziz (2015). Effect of acute caffeine supplementation on anaerobic power and blood lactate levels in female athletes.. Journal of caffeine research, 5, 83-87. Link: 10.1089/JCR.2014.0034
56. M. Jackman, P. Wendling, D. Friars, T. Graham (1996). Metabolic catecholamine, and endurance responses to caffeine during intense exercise.. Journal of applied physiology, 81 4,
    1658-63 . Link: 10.1152/JAPPL.1996.81.4.1658
57. Asghar Keshavarz Siahpoosh, Amin Nesaei (2016). The Effect of Caffeine Supplementation on Blood Lactate and Glucose after 800 and 1500 meter Run. Biomedical and Pharmacology Journal, 9, 97-103. Link: 10.13005/BPJ/914
58. M. Crowe, A. Leicht, W. Spinks (2006). Physiological and cognitive responses to caffeine during repeated, high-intensity exercise.. International journal of sport nutrition and exercise metabolism, 16 5,
    528-44 . Link: 10.1123/IJSNEM.16.5.528
59. F. Anselme, Katia Collomp, B. Mercier, Said Ahmaidi, C. Prefaut (2004). Caffeine increases maximal anaerobic power and blood lactate concentration. European Journal of Applied Physiology and Occupational Physiology, 65, 188-191. Link: 10.1007/BF00705079
60. K. Abbotts, T. Ewell, M. Bomar, H. Butterklee, C. Bell (2023). Caffeine Augments the Lactate and Interleukin-6 Response to Moderate-Intensity Exercise. Medicine & Science in Sports & Exercise, 55, 982 - 990. Link: 10.1249/MSS.0000000000003121
61. T. Hartley, W. Lovallo, T. Whitsett (2004). Cardiovascular effects of caffeine in men and women.. The American journal of cardiology, 93 8,
    1022-6 . Link: 10.1016/J.AMJCARD.2003.12.057
62. A. Mesas, L. León-Muñoz, F. Rodríguez‐Artalejo, E. López-García (2011). The effect of coffee on blood pressure and cardiovascular disease in hypertensive individuals: a systematic review and meta-analysis.. The American journal of clinical nutrition, 94 4,
    1113-26 . Link: 10.3945/ajcn.111.016667
63. M. Noordzij, C. Uiterwaal, L. Arends, F. Kok, D. Grobbee, J. Geleijnse (2005). Blood pressure response to chronic intake of coffee and caffeine: a meta-analysis of randomized controlled trials. Journal of Hypertension, 23, 921–928. Link: 10.1097/01.hjh.0000166828.94699.1d
64. B. Sung, B. Sung, William R. Lovallo, William R. Lovallo, G. A. Pincomb, G. A. Pincomb, Michael F. Wilson, Michael F. Wilson (1990). Effects of caffeine on blood pressure response during exercise in normotensive healthy young men.. The American journal of cardiology, 65 13,
    909-13 . Link: 10.1016/0002-9149(90)91435-9
65. J. D. Lane, B. Phillips-bute, C. Pieper (1998). Caffeine Raises Blood Pressure at Work. Psychosomatic Medicine, 60, 327-330. Link: 10.1097/00006842-199805000-00019
66. S. Ketelhut, Carole Gassner, C. Nigg (2022). EFFECTS OF CAFFEINE ON BLOOD PRESSURE AND HEART RATE VARIABILITY AT REST AND DURING COLD PRESSOR TEST. Journal of Hypertension, 40, e234. Link: 10.1097/01.hjh.0000837876.08919.cf
67. G. A. Pincomb, W. Lovallo, R. Passey, M. Wilson (1988). Effect of behavior state on caffeine's ability to alter blood pressure.. The American journal of cardiology, 61 10,
    798-802 . Link: 10.1016/0002-9149(88)91069-7
68. W. Greenberg, D. Shapiro (1987). The effects of caffeine and stress on blood pressure in individuals with and without a family history of hypertension.. Psychophysiology, 24 2,
    151-6 . Link: 10.1111/J.1469-8986.1987.TB00269.X
69. Peter J. Green, R. Kirby, J. Suls (1996). The effects of caffeine on blood pressure and heart rate: A review. Annals of Behavioral Medicine, 18, 201-216. Link: 10.1007/BF02883398
70. Marja-Leena Nurminen, Leena Niittynen, R. Korpela, Heikki Vapaatalo (1999). Coffee, caffeine and blood pressure: a critical review. European Journal of Clinical Nutrition, 53, 831-839. Link: 10.1038/sj.ejcn.1600899
71. W. Lovallo, T. Whitsett, M. al’Absi, B. Sung, A. Vincent, Michael F. Wilson (2005). Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels. Psychosomatic Medicine, 67, 734-739. Link: 10.1097/01.psy.0000181270.20036.06
72. C. Beaven, W. Hopkins, K. T. Hansen, M. R. Wood, J. Cronin, T. Lowe (2008). Dose effect of caffeine on testosterone and cortisol responses to resistance exercise.. International journal of sport nutrition and exercise metabolism, 18 2,
    131-41 . Link: 10.1123/IJSNEM.18.2.131
73. W. Lovallo, M. al’Absi, K. Blick, T. Whitsett, Michael F. Wilson (1996). Stress-like adrenocorticotropin responses to caffeine in young healthy men. Pharmacology Biochemistry and Behavior, 55, 365-369. Link: 10.1016/S0091-3057(96)00105-0
74. W. Lovallo, G. A. Pincomb, B. Sung, R. Passey, K. P. Sausen, Michael F. Wilson (1989). Caffeine May Potentiate Adrenocortical Stress Responses in Hypertension‐Prone Men. Hypertension, 14, 170–176. Link: 10.1161/01.HYP.14.2.170
75. J. D. Lane (1994). Neuroendocrine responses to caffeine in the work environment.. Psychosomatic Medicine, 56, 267–270. Link: 10.1097/00006842-199405000-00014
76. N. Rieth, N. Vibarel-Rebot, Corinne Buisson, C. Jaffré, Katia Collomp (2016). Caffeine and saliva steroids in young healthy recreationally trained women: impact of regular caffeine intake. Endocrine, 52, 391-394. Link: 10.1007/s12020-015-0780-x
77. T. Mackenzie, R. Comi, P. Sluss, Ronit Keisari, S. Manwar, Janice Kim, R. Larson, J. Baron (2007). Metabolic and hormonal effects of caffeine: randomized, double-blind, placebo-controlled crossover trial.. Metabolism: clinical and experimental, 56 12,
    1694-8 . Link: 10.1016/J.METABOL.2007.07.013
78. A. Gavrieli, M. Yannakoulia, E. Fragopoulou, Dimitris Margaritopoulos, J. Chamberland, P. Kaisari, S. Kavouras, C. Mantzoros (2011). Caffeinated coffee does not acutely affect energy intake, appetite, or inflammation but prevents serum cortisol concentrations from falling in healthy men.. The Journal of nutrition, 141 4,
    703-7 . Link: 10.3945/jn.110.137323
79. M. al’Absi, W. Lovallo, B. Mckey, B. Sung, T. Whitsett, Michael F. Wilson (1998). Hypothalamic-Pituitary-Adrenocortical Responses to Psychological Stress and Caffeine in Men at High and Low Risk for Hypertension. Psychosomatic Medicine, 60, 521-527. Link: 10.1097/00006842-199807000-00021
80. W. Lovallo, N. Farag, A. Vincent, T. L. Thomas, Michael F. Wilson (2006). Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women. Pharmacology Biochemistry and Behavior, 83, 441-447. Link: 10.1016/j.pbb.2006.03.005
81. Ruishan Sun, Jun-ya Sun, Jingqiang Li, Shuwen Li (2022). Effects of caffeine ingestion on physiological indexes of human neuromuscular fatigue: A systematic review and meta‐analysis. Brain and Behavior, 12, . Link: 10.1002/brb3.2529
82. S. Ataka, Masaaki Tanaka, S. Nozaki, H. Mizuma, K. Mizuno, Tsuyoshi Tahara, T. Sugino, T. Shirai, Y. Kajimoto, H. Kuratsune, O. Kajimoto, Yasuyoshi Watanabe (2008). Effects of oral administration of caffeine and D-ribose on mental fatigue.. Nutrition, 24 3,
    233-8 . Link: 10.1016/j.nut.2007.12.002
83. Petey W. Mumford, Aaron C. Tribby, C. Poole, V. Dalbo, A. Scanlan, J. Moon, M. Roberts, Kaelin C. Young (2016). Effect of Caffeine on Golf Performance and Fatigue during a Competitive Tournament.. Medicine and science in sports and exercise, 48 1,
    132-8 . Link: 10.1249/MSS.0000000000000753
84. L. C. Felippe, G. Ferreira, Sara Learsi, D. Boari, R. Bertuzzi, A. Lima-Silva (2018). Caffeine increases both total work performed above critical power and peripheral fatigue during a 4-km cycling time trial.. Journal of applied physiology, 124 6,
    1491-1501 . Link: 10.1152/japplphysiol.00930.2017
85. J. Temple, D. Hostler, C. Martin-Gill, C. Moore, Patricia M. Weiss, Denisse J. Sequeira, Joseph P. Condle, E. Lang, J. S. Higgins, P. D. Patterson (2018). Systematic Review and Meta-analysis of the Effects of Caffeine in Fatigued Shift Workers: Implications for Emergency Medical Services Personnel. Prehospital Emergency Care, 22, 37 - 46. Link: 10.1080/10903127.2017.1382624
86. Lena Herden, R. Weissert (2020). The Effect of Coffee and Caffeine Consumption on Patients with Multiple Sclerosis-Related Fatigue. Nutrients, 12, . Link: 10.3390/nu12082262
87. M. Lorist, M. Tops (2003). Caffeine, fatigue, and cognition. Brain and Cognition, 53, 82-94. Link: 10.1016/S0278-2626(03)00206-9
88. R. Azevedo, M. D. Silva-Cavalcante, B. Gualano, A. Lima-Silva, R. Bertuzzi (2016). Effects of caffeine ingestion on endurance performance in mentally fatigued individuals. European Journal of Applied Physiology, 116, 2293-2303. Link: 10.1007/s00421-016-3483-y
89. Daniel T Fuller, Matthew Lee Smith, A. Boolani (2021). Trait Energy and Fatigue Modify the Effects of Caffeine on Mood, Cognitive and Fine-Motor Task Performance: A Post-Hoc Study. Nutrients, 13, . Link: 10.3390/nu13020412
90. Chelsea J. Hahn, A. Jagim, C. Camic, Matthew J. Andre (2018). Acute Effects of a Caffeine-Containing Supplement on Anaerobic Power and Subjective Measurements of Fatigue in Recreationally Active Men. Journal of Strength and Conditioning Research, 32, 1029–1035. Link: 10.1519/JSC.0000000000002442
91. Carlos Ruíz-Moreno, Jorge Gutiérrez-Hellín, F. Amaro-Gahete, Jaime González-García, Verónica Giráldez-Costas, Víctor Pérez-García, J. Del Coso (2020). Caffeine increases whole-body fat oxidation during 1 h of cycling at Fatmax. European Journal of Nutrition, 60, 2077 - 2085. Link: 10.1007/s00394-020-02393-z
92. Simeng Zhang, Jiro Takano, N. Murayama, Morie Tominaga, T. Abe, Insung Park, Jaehoon Seol, Asuka Ishihara, Yoshiaki Tanaka, Katsuhiko Yajima, Yoko Suzuki, C. Suzuki, S. Fukusumi, M. Yanagisawa, Toshio Kokubo, K. Tokuyama (2020). Subacute Ingestion of Caffeine and Oolong Tea Increases Fat Oxidation without Affecting Energy Expenditure and Sleep Architecture: A Randomized, Placebo-Controlled, Double-Blinded Cross-Over Trial. Nutrients, 12, . Link: 10.3390/nu12123671
93. K. Acheson, G. Gremaud, I. Meirim, F. Montigon, Y. Krebs, L. Fay, L. Gay, P. Schneiter, C. Schindler, L. Tappy (2004). Metabolic effects of caffeine in humans: lipid oxidation or futile cycling?. The American journal of clinical nutrition, 79 1,
    40-6 . Link: 10.1093/AJCN/79.1.40
94. K. Acheson, B. Zahorska‐Markiewicz, P. Pittet, K. Anantharaman, E. Jéquier (1980). Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals.. The American journal of clinical nutrition, 33 5,
    989-97 . Link: 10.1093/AJCN/33.5.989
95. Mauricio Ramírez-Maldonado, L. Jurado-Fasoli, J. Del Coso, Jonatan R. Ruiz, F. Amaro-Gahete (2021). Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation?. Journal of the International Society of Sports Nutrition, 18, . Link: 10.1186/s12970-020-00400-6
96. D. Collado-Mateo, Ana Myriam Lavín-Pérez, E. Merellano-Navarro, J. Coso (2020). Effect of Acute Caffeine Intake on the Fat Oxidation Rate during Exercise: A Systematic Review and Meta-Analysis. Nutrients, 12, . Link: 10.3390/nu12123603
97. R. Hursel, Wolfgang Viechtbauer, A. G. Dulloo, Angelo Tremblay, Luc Tappy, W. Rumpler, M. Westerterp-Plantenga (2011). The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta‐analysis. Obesity Reviews, 12, . Link: 10.1111/j.1467-789X.2011.00862.x
98. Jorge Gutiérrez-Hellín, Carlos Ruíz-Moreno, Millán Aguilar-Navarro, Alejandro Muñoz, D. Varillas-Delgado, F. Amaro-Gahete, Justin D Roberts, J. Del Coso (2021). Placebo Effect of Caffeine on Substrate Oxidation during Exercise. Nutrients, 13, . Link: 10.3390/nu13030782
99. D. Nieman, M. Kohlmeier, Andrew J Simonson, W. Sha, Camila A Sakaguchi, Tondra Blevins, Jaina Hattabaugh (2019). Acute Ingestion of a Mixed Flavonoid and Caffeine Supplement Increases Energy Expenditure and Fat Oxidation in Adult Women: A Randomized, Crossover Clinical Trial (OR29-07-19).. Current developments in nutrition, 3 Suppl 1, . Link: 10.1093/cdn/nzz031.OR29-07-19
100. S. Conger, Lara M. Tuthill, M. Millard-Stafford (2022). Does Caffeine Increase Fat Metabolism? A Systematic Review and Meta-Analysis.. International journal of sport nutrition and exercise metabolism, ,
     1-9 . Link: 10.1123/ijsnem.2022-0131
101. T. Robertson, M. Clifford, S. Penson, G. Chope, M. Robertson (2015). A single serving of caffeinated coffee impairs postprandial glucose metabolism in overweight men. British Journal of Nutrition, 114, 1218 - 1225. Link: 10.1017/S0007114515002640
102. Lisa Dewar, R. Heuberger (2017). The effect of acute caffeine intake on insulin sensitivity and glycemic control in people with diabetes.. Diabetes & metabolic syndrome, 11 Suppl 2,
     S631-S635 . Link: 10.1016/j.dsx.2017.04.017
103. Xinxin Zheng, Yan-lu Xu, S. Li, R. Hui, Yong-Jian Wu, Xiao-hong Huang (2013). Effects of green tea catechins with or without caffeine on glycemic control in adults: a meta-analysis of randomized controlled trials.. The American journal of clinical nutrition, 97 4,
     750-62 . Link: 10.3945/ajcn.111.032573
104. A. Pizziol, V. Tikhonoff, C. D. Paleari, E. Russo, Alberto Mazza, G. Ginocchio, C. Onesto, L. Pavan, Edoardo Casiglia, A. Pessina (1998). Effects of caffeine on glucose tolerance: A placebo-controlled study. European Journal of Clinical Nutrition, 52, 846-849. Link: 10.1038/sj.ejcn.1600657
105. J. Watson, Emma Jenkins, P. Hamilton, Michael J. Lunt, David Kerr (2000). Influence of caffeine on the frequency and perception of hypoglycemia in free-living patients with type 1 diabetes.. Diabetes care, 23 4,
     455-9 . Link: 10.2337/DIACARE.23.4.455
106. N. Whitehead, H. White (2013). Systematic review of randomised controlled trials of the effects of caffeine or caffeinated drinks on blood glucose concentrations and insulin sensitivity in people with diabetes mellitus.. Journal of human nutrition and dietetics : the official journal of the British Dietetic Association, 26 2,
     111-25 . Link: 10.1111/jhn.12033
107. S. Rosenkranz, Olivet Martinez, Trevor J. Steele, S. Emerson, B. Cull, S. Kurti (2019). Glycemic Control Outcomes Following Three Weeks of Added Sugar-Sweetened Beverages or 100% Fruit Juice: A Randomized Controlled Trial (P12-015-19).. Current developments in nutrition, 3 Suppl 1, . Link: 10.1093/cdn/nzz035.P12-015-19
108. J. D. Lane, C. Barkauskas, R. Surwit, M. Feinglos (2004). Caffeine impairs glucose metabolism in type 2 diabetes.. Diabetes care, 27 8,
     2047-8 . Link: 10.2337/DIACARE.27.8.2047
109. L. Moisey, S. Kacker, A. C. Bickerton, L. Robinson, T. Graham (2008). Caffeinated coffee consumption impairs blood glucose homeostasis in response to high and low glycemic index meals in healthy men.. The American journal of clinical nutrition, 87 5,
     1254-61 . Link: 10.1093/AJCN/87.5.1254
110. K. Johnston, M. Clifford, L. Morgan (2003). Coffee acutely modifies gastrointestinal hormone secretion and glucose tolerance in humans: glycemic effects of chlorogenic acid and caffeine.. The American journal of clinical nutrition, 78 4,
     728-33 . Link: 10.1093/AJCN/78.4.728
111. H. Sondermeijer, A. G. J. van Marle, P. Kamen, H. Krum (2002). Acute effects of caffeine on heart rate variability.. The American journal of cardiology, 90 8,
     906-7 . Link: 10.1016/S0002-9149(02)02725-X
112. P. Zuchinali, G. Souza, M. Pimentel, D. Chemello, A. Zimerman, Vanessa Giaretta, Joyce Salamoni, B. Fracasso, L. Zimerman, L. Rohde (2016). Short-term Effects of High-Dose Caffeine on Cardiac Arrhythmias in Patients With Heart Failure: A Randomized Clinical Trial.. JAMA internal medicine, 176 12,
     1752-1759 . Link: 10.1001/jamainternmed.2016.6374
113. Peter J. Green, R. Kirby, J. Suls (1996). The effects of caffeine on blood pressure and heart rate: A review. Annals of Behavioral Medicine, 18, 201-216. Link: 10.1007/BF02883398
114. G. K. Karapetian, Hermann J. Engels, K. Gretebeck, R. Gretebeck (2012). Effect of Caffeine on LT, VT and HRVT. International Journal of Sports Medicine, 33, 507 - 513. Link: 10.1055/s-0032-1301904
115. V. Yeragani, S. Krishnan, H. Engels, R. Gretebeck (2005). Effects of caffeine on linear and nonlinear measures of heart rate variability before and after exercise. Depression and Anxiety, 21, . Link: 10.1002/da.20061
116. J. L. Flueck, F. Schaufelberger, M. Lienert, Daniela Schäfer Olstad, M. Wilhelm, C. Perret (2016). Acute Effects of Caffeine on Heart Rate Variability, Blood Pressure and Tidal Volume in Paraplegic and Tetraplegic Compared to Able-Bodied Individuals: A Randomized, Blinded Trial. PLoS ONE, 11, . Link: 10.1371/journal.pone.0165034
117. J. D. Lane, C. Pieper, B. Phillips-bute, J. E. Bryant, C. Kuhn (2002). Caffeine Affects Cardiovascular and Neuroendocrine Activation at Work and Home. Psychosomatic Medicine, 64, 595-603. Link: 10.1097/01.PSY.0000021946.90613.DB
118. S. Ketelhut, Carole Gassner, C. Nigg (2022). EFFECTS OF CAFFEINE ON BLOOD PRESSURE AND HEART RATE VARIABILITY AT REST AND DURING COLD PRESSOR TEST. Journal of Hypertension, 40, e234. Link: 10.1097/01.hjh.0000837876.08919.cf
119. Cagney T Sargent, Tareq K Shahbal, A. E. Carrillo, T. Amorim, Jason R. Edsall, Emily J. Ryan, E. Ryan (2022). Effects of Low Dose Caffeine on Post-Exercise Heart Rate Variability: A Double-Blind Placebo-Controlled Trial.. International journal of exercise science, 15 2,
     103-112 . Link:
120. J. W. Daniels, P. Molé, J. D. Shaffrath, C. L. Stebbins (1998). Effects of caffeine on blood pressure, heart rate, and forearm blood flow during dynamic leg exercise.. Journal of applied physiology, 85 1,
     154-9 . Link: 10.1152/JAPPL.1998.85.1.154
121. P. Azevedo, Matheus G. D. Oliveira, K. Tanaka, P. Pereira, G. Esteves, M. Tenan (2019). Perceived exertion and performance modulation: effects of caffeine ingestion and subject expectation.. The Journal of sports medicine and physical fitness, , . Link: 10.31236/osf.io/us3vq
122. J. Grgic, P. Mikulic (2017). Caffeine ingestion acutely enhances muscular strength and power but not muscular endurance in resistance-trained men. European Journal of Sport Science, 17, 1029 - 1036. Link: 10.1080/17461391.2017.1330362
123. S. Backhouse, S. Biddle, N. Bishop, Clyde Williams (2011). Caffeine ingestion, affect and perceived exertion during prolonged cycling. Appetite, 57, 247-252. Link: 10.1016/j.appet.2011.05.304
124. Taís Tavares Ferreira, João Vitor Farias da Silva, N. Bueno (2020). Effects of caffeine supplementation on muscle endurance, maximum strength, and perceived exertion in adults submitted to strength training: a systematic review and meta-analyses. Critical Reviews in Food Science and Nutrition, 61, 2587 - 2600. Link: 10.1080/10408398.2020.1781051
125. L. Rodrigues, Russo Ak, S. Ac, Piçarro Ic, Silva Fr, Zogaib Ps, D. Soares (1990). Effects of caffeine on the rate of perceived exertion.. Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas, 23 10,
     965-8 . Link:
126. Kevin J. Cole, D. Costill, R. D. Starling, B. Goodpaster, Scott W. Trappe, W. Fink (1996). Effect of caffeine ingestion on perception of effort and subsequent work production.. International journal of sport nutrition, 6 1,
     14-23 . Link: 10.1123/IJSN.6.1.14
127. B. Denadai, M. L. Denadai (1998). Effects of caffeine on time to exhaustion in exercise performed below and above the anaerobic threshold.. Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas, 31 4,
     581-5 . Link: 10.1590/S0100-879X1998000400017
128. Marios Hadjicharalambous, E. Georgiades, L. Kilduff, A. Turner, F. Tsofliou, Y. Pitsiladis (2006). Influence of caffeine on perception of effort, metabolism and exercise performance following a high-fat meal. Journal of Sports Sciences, 24, 875 - 887. Link: 10.1080/02640410500249399
129. Laurent Green, J. Green, P. Wickwire, J. McLester, Shawn C. Gendle, G. Hudson, R. Pritchett, C. Laurent (2007). Effects of caffeine on repetitions to failure and ratings of perceived exertion during resistance training.. International journal of sports physiology and performance, 2 3,
     250-9 . Link: 10.1123/IJSPP.2.3.250
130. M. Doherty, P. Smith (2005). Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta‐analysis. Scandinavian Journal of Medicine & Science in Sports, 15, . Link: 10.1111/j.1600-0838.2005.00445.x
131. L. Chait, R. Griffiths (1983). Effects of caffeine on cigarette smoking and subjective response. Clinical Pharmacology & Therapeutics, 34, . Link: 10.1038/clpt.1983.223
132. E. Childs, H. Wit (2006). Subjective, behavioral, and physiological effects of acute caffeine in light, nondependent caffeine users. Psychopharmacology, 185, 514-523. Link: 10.1007/s00213-006-0341-3
133. K. Rees, D. Allen, M. Lader (1999). The influences of age and caffeine on psychomotor and cognitive function. Psychopharmacology, 145, 181-188. Link: 10.1007/s002130051047
134. P. Harrell, L. M. Juliano (2009). Caffeine expectancies influence the subjective and behavioral effects of caffeine. Psychopharmacology, 207, 335-342. Link: 10.1007/s00213-009-1658-5
135. W. Pritchard, J. Robinson, J. D. Debethizy, Riley A. Davis, M. Stiles (1995). Caffeine and smoking: subjective, performance, and psychophysiological effects.. Psychophysiology, 32 1,
     19-27 . Link: 10.1111/J.1469-8986.1995.TB03401.X
136. K. N. Stern, L. Chait, C. Johanson (2004). Reinforcing and subjective effects of caffeine in normal human volunteers. Psychopharmacology, 98, 81-88. Link: 10.1007/BF00442010
137. Andrew P. Smith, D. Sutherland, G. Christopher (2005). Effects of repeated doses of caffeine on mood and performance of alert and fatigued volunteers. Journal of Psychopharmacology, 19, 620 - 626. Link: 10.1177/0269881105056534
138. R. Domínguez, Pablo Veiga-Herreros, A. Sánchez-Oliver, Juan José Montoya, J. Ramos-Álvarez, F. Miguel-tobal, Ángel Lago-Rodríguez, Pablo Jodra (2021). Acute Effects of Caffeine Intake on Psychological Responses and High-Intensity Exercise Performance. International Journal of Environmental Research and Public Health, 18, . Link: 10.3390/ijerph18020584
139. A. Adan, Gemma Prat, M. Fabbri, M. Sánchez‐Turet (2008). Early effects of caffeinated and decaffeinated coffee on subjective state and gender differences. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 32, 1698-1703. Link: 10.1016/j.pnpbp.2008.07.005
140. M. Bruce, N. Scott, M. Lader, V. Marks (1986). The psychopharmacological and electrophysiological effects of single doses of caffeine in healthy human subjects.. British journal of clinical pharmacology, 22 1,
     81-7 . Link: 10.1111/J.1365-2125.1986.TB02883.X
141. Taylor Landry, M. Saunders, Jeremy D. Akers, C. Womack (2019). Caffeine added to coffee does not alter the acute testosterone response to exercise in resistance trained males.. The Journal of sports medicine and physical fitness, 59 9,
     1435-1441 . Link: 10.23736/S0022-4707.19.09183-7
142. C. Beaven, W. Hopkins, K. T. Hansen, M. R. Wood, J. Cronin, T. Lowe (2008). Dose effect of caffeine on testosterone and cortisol responses to resistance exercise.. International journal of sport nutrition and exercise metabolism, 18 2,
     131-41 . Link: 10.1123/IJSNEM.18.2.131
143. Nicole M Wedick, C. Mantzoros, E. Ding, A. Brennan, B. Rosner, E. Rimm, F. Hu, R. V. van Dam (2012). The effects of caffeinated and decaffeinated coffee on sex hormone-binding globulin and endogenous sex hormone levels: a randomized controlled trial. Nutrition Journal, 11, 86 - 86. Link: 10.1186/1475-2891-11-86
144. Serkan Karaismailoglu, Meltem Tuncer, Sibel Bayrak, G. Erdogan, EL Ergun, Ayşen Erdem (2017). The perinatal effects of maternal caffeine intake on fetal and neonatal brain levels of testosterone, estradiol, and dihydrotestosterone in rats. Naunyn-Schmiedeberg's Archives of Pharmacology, 390, 827 - 838. Link: 10.1007/s00210-017-1383-2
145. R. Ferrini, Elizabeth Barrett-Connor (1996). Caffeine intake and endogenous sex steroid levels in postmenopausal women. The Rancho Bernardo Study.. American journal of epidemiology, 144 7,
     642-4 . Link: 10.1093/OXFORDJOURNALS.AJE.A008975
146. C. M. Donald, Joss Moore, Alan McIntyre, Kevin Carmody, B. Donne (2017). Acute Effects of 24-h Sleep Deprivation on Salivary Cortisol and Testosterone Concentrations and Testosterone to Cortisol Ratio Following Supplementation with Caffeine or Placebo. International Journal of Exercise Science, 10, 108 - 120. Link:
147. Russell M, Reynolds N A, Crewther B T, Cook C J, K. L (2020). The Physiological and Performance Effects of Caffeine Gum Consumed During A Simulated Half-Time By Professional Academy Rugby Union Players.. Journal of Strength and Conditioning Research, , . Link: 10.1519/JSC.0000000000002185
148. Wuebbles Bh (2015). Dose effects of caffeine ingestion on acute hormonal responses to resistance exercise.. Journal of Sports Medicine and Physical Fitness, 55, 1242-1251. Link:
149. C. Paton, T. Lowe, A. Irvine (2010). Caffeinated chewing gum increases repeated sprint performance and augments increases in testosterone in competitive cyclists. European Journal of Applied Physiology, 110, 1243-1250. Link: 10.1007/s00421-010-1620-6
150. Aleksandra Filip-Stachnik, M. Krzysztofik, J. Del Coso, T. Pałka, E. Sadowska-Krępa (2023). The Effect of Acute Caffeine Intake on Resistance Training Volume, Prooxidant-Antioxidant Balance and Muscle Damage Markers Following a Session of Full-Body Resistance Exercise in Resistance-Trained Men Habituated to Caffeine.. Journal of sports science & medicine, 22 3,
     436-446 . Link: 10.52082/jssm.2023.435
151. Louise Jones, Iona Johnstone, Charlotte Day, Sasha Le Marquer, A. Hulton (2021). The Dose-Effects of Caffeine on Lower Body Maximal Strength, Muscular Endurance, and Rating of Perceived Exertion in Strength-Trained Females. Nutrients, 13, . Link: 10.3390/nu13103342
152. T. Graham, E. Hibbert, P. Sathasivam (1998). Metabolic and exercise endurance effects of coffee and caffeine ingestion.. Journal of applied physiology, 85 3,
     883-9 . Link: 10.1152/JAPPL.1998.85.3.883
153. M. Mohr, J. Nielsen, J. Bangsbo (2011). Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation.. Journal of applied physiology, 111 5,
     1372-9 . Link: 10.1152/japplphysiol.01028.2010
154. Verónica Giráldez-Costas, Jaime González-García, B. Lara, J. Coso, M. Wilk, J. Salinero (2020). Caffeine Increases Muscle Performance During a Bench Press Training Session. Journal of Human Kinetics, 74, 185 - 193. Link: 10.2478/hukin-2020-0024
155. F. Rossi, V. Panissa, Paula A. Monteiro, J. Gerosa-Neto, É. Caperuto, J. Cholewa, A. Zagatto, F. Lira (2017). Caffeine supplementation affects the immunometabolic response to concurrent training. Journal of Exercise Rehabilitation, 13, 179 - 184. Link: 10.12965/jer.1734938.445
156. Mírian Vaz Valério, G. Z. Schaun, L. S. Andrade, G. B. David, R. Orcy, A. Rombaldi, C. Alberton (2023). Caffeine Supplementation Effects on Concurrent Training Performance in Resistance-Trained Men: A Double-Blind Placebo-Controlled Crossover Study.. Research quarterly for exercise and sport, ,
     1-9 . Link: 10.1080/02701367.2023.2276401
157. V. Fernández-Elías, J. Del Coso, N. Hamouti, J. Ortega, Gloria Muñoz, J. Muñoz-Guerra, R. Mora‐Rodriguez (2015). Ingestion of a moderately high caffeine dose before exercise increases postexercise energy expenditure.. International journal of sport nutrition and exercise metabolism, 25 1,
     46-53 . Link: 10.1123/ijsnem.2014-0037
158. K. Abbotts, T. Ewell, M. Bomar, H. Butterklee, J. Rebik, Christopher Bell (2022). Caffeine Augments the Lactate and Interleukin‐6 Response to Moderate‐Intensity Exercise in Men But Not Women. The FASEB Journal, 36, . Link: 10.1096/fasebj.2022.36.s1.r2033
159. E. Lattari, Lucas A. F. Vieira, L. E. R. Santos, Marco Antonio Jesus Abreu, G. Rodrigues, Bruno Ribeiro Ramalho de Oliveira, Sérgio Machado, G. M. Maranhao Neto, T. M. Santos (2022). Transcranial Direct Current Stimulation Combined With or Without Caffeine: Effects on Training Volume and Pain Perception. Research Quarterly for Exercise and Sport, 94, 45 - 54. Link: 10.1080/02701367.2021.1939251
160. J. Walsh, M. Muehlbach, Tina M. Humm, Q. Stokes Dickins, J. Sugerman, P. Schweitzer (2005). Effect of caffeine on physiological sleep tendency and ability to sustain wakefulness at night. Psychopharmacology, 101, 271-273. Link: 10.1007/BF02244139
161. J. Weibel, Yu-Shiuan Lin, H. Landolt, C. Garbazza, V. Kolodyazhniy, Joshua Kistler, S. Rehm, K. Rentsch, S. Borgwardt, C. Cajochen, C. Reichert (2019). Caffeine-dependent changes of sleep-wake regulation: Evidence for adaptation after repeated intake. Progress in Neuro-Psychopharmacology and Biological Psychiatry, 99, . Link: 10.1101/641480
162. J. Wyatt, C. Cajochen, A. Ritz-de Cecco, C. Czeisler, D. Dijk (2004). Low-dose repeated caffeine administration for circadian-phase-dependent performance degradation during extended wakefulness.. Sleep, 27 3,
     374-81 . Link: 10.1093/SLEEP/27.3.374
163. H. V. Dongen, N. J. Price, J. Mullington, M. Szuba, S. Kapoor, D. Dinges (2001). Caffeine eliminates psychomotor vigilance deficits from sleep inertia.. Sleep, 24 7,
     813-9 . Link: 10.1093/SLEEP/24.7.813
164. C. Grant, A. Coates, J. Dorrian, G. Paech, M. Pajcin, C. Della Vedova, Kayla T. Johnson, G. Kamimori, J. Fidock, E. Aidman, S. Banks (2018). The impact of caffeine consumption during 50 hr of extended wakefulness on glucose metabolism, self‐reported hunger and mood state. Journal of Sleep Research, 27, . Link: 10.1111/jsr.12681
165. Ian Clark, H. Landolt (2017). Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials.. Sleep medicine reviews, 31,
     70-78 . Link: 10.1016/j.smrv.2016.01.006
166. Janine Weibel, Yu-Shiuan Lin, Hans-Peter Landolt, Corrado Garbazza, Vitaliy Kolodyazhniy, Joshua Kistler, Sophia Rehm, Katharina Rentsch, Stefan Borgwardt, Christian Cajochen, Carolin Franziska Reichert (2020). Caffeine-dependent changes of sleep-wake regulation: Evidence for adaptation after repeated intake. Progress in Neuro-Psychopharmacology and Biological Psychiatry, , . Link: 10.1016/j.pnpbp.2019.109851
167. M. Beaumont, D. Batéjat, C. Piérard, O. Coste, P. Doireau, P. Beers, F. Chauffard, D. Chassard, M. Enslen, J. Denis, D. Lagarde (2001). Slow release caffeine and prolonged (64‐h) continuous wakefulness: effects on vigilance and cognitive performance. Journal of Sleep Research, 10, . Link: 10.1046/j.1365-2869.2001.00266.x
168. A. Goldstein, R. Warren, S. Kaizer (1965). PSYCHOTROPIC EFFECTS OF CAFFEINE IN MAN. I. INDIVIDUAL DIFFERENCES IN SENSITIVITY TO CAFFEINE-INDUCED WAKEFULNESS.. The Journal of pharmacology and experimental therapeutics, 149,
     156-9 . Link:
169. H. Landolt, J. Rétey, Karin Tönz, J. Gottselig, R. Khatami, Isabelle Buckelmüller, P. Achermann (2004). Caffeine Attenuates Waking and Sleep Electroencephalographic Markers of Sleep Homeostasis in Humans. Neuropsychopharmacology, 29, 1933-1939. Link: 10.1038/sj.npp.1300526