Article by Sella Khouri, McGill Dietetics Student
What is caffeine:
Caffeine, a xanthine alkaloid compound, is consumed widely and daily by humans. It is a popular stimulant worldwide that is frequently consumed to enhance mood, alertness, muscle endurance, exercise performance, and work productivity.
Caffeine is a natural ingredient found in coffee beans, tea leaves, cocoa beans, guarana, kola nuts and yerba mate Caffeine can also be synthesized and is added to foods and beverages, including soft drinks, energy drinks, and energy shots, and to tablets marketed for reducing fatigue. Coffee and tea are among the most popular beverages worldwide and contain substantial amounts of caffeine. These beverages have been consumed for hundreds of years and have become an important part of cultural traditions and social life.
How does caffeine impact our bodies:
Caffeine has many impacts on our bodies and has numerous physiological effects, including cardiovascular, respiratory, renal, and smooth muscle, as well as effects on mood, memory, alertness, and physical and cognitive performance.
The molecular structure of caffeine is similar to that of adenosine, which allows caffeine to bind to adenosine receptors inhibiting the effects of adenosine. Therefore, caffeine intake triggers arousal and alertness, improves mood, and causes the release of catecholamines, which induce beneficial effects on human behavior. Nevertheless, caffeine has been related to other beneficial effects such as antioxidant and anti-inflammatory actions that are important to human health.
A recent study showed that caffeine taken 0.5–4 h prior to a meal may suppress acute energy intake. Therefore, caffeine may play a role in energy balance by reducing appetite and increasing the basal metabolic rate and food-induced thermogenesis.
In addition, studies had shown that caffeine can reduce the risk of several diseases, such as Alzheimer and Parkinson disease. It also plays a mild diuretic effect by inhibiting fluid reabsorption along proximal renal tubules.
In terms of the relationship between caffeine and kidney stones, data from 3 large cohort studies have reported the association between caffeine consumption and a lower risk of kidney stone disease despite caffeine-rich beverages have been recognized to contain oxalate and increase urinary calcium excretion.
Safe amounts:
| Age Group | Recommended maximum daily intake |
| Adults (18 years and over) | 400 mg |
| People planning to become pregnant | 300 mg |
| People who are pregnant | 300 mg |
| People who are breastfeeding | 300 mg |
| Children and adolescents (up to 18 years) | 2.5 mg per kg of body weight |
Side effects of excessive intake:
Some people are more sensitive to caffeine than others. Caffeine can leave you feeling nervous or anxious particularly at high doses (>200 mg per occasion or >400 mg per day), increase your heartbeat or give you a headache. Caffeine consumption later in the day can increase sleep latency and reduce the quality of sleep all of which can hurt your performance. If you get any of these symptoms, try a smaller dose or simply avoid it.
If you regularly include caffeine in your diet and you suddenly stop having it, you may have withdrawal effects such as headaches or drowsiness.
Caffeine in the form of energy drinks and shots may have more adverse effects than other caffeinated beverages since these beverages can be consumed very quickly, and the caffeine is released into your bloodstream rapidly unlike hot coffee or tea which can be sipped slowly. Another factor could be due to lack of clarity on the part of consumers about caffeine content.
Caffeine and exercise:
Caffeine intake has also shown ergogenic effects, which are attributed to different factors, such as enhanced substrate utilization, fatigue delay, and alertness. Caffeine stimulates the central nervous system and improves muscle contraction and some motor skills. Therefore, it may help by making exercise feel easier, increasing endurance and improving short-term high-intensity performance. Caffeine can be taken before or during exercise to feel the benefits.
Research show that 1 to 3 mg of caffeine per kg (0.5 to 1.4 mg per lb) body weight taken before or during exercise may improve performance. For a 70 kg (154 lb) person, this equals 70 to 210 mg caffeine, which is the amount found in 1 cup of brewed coffee.
References:
Barcelos, R. P., Lima, F. D., Carvalho, N. R., Bresciani, G., & Royes, L. F. (2020). Caffeine effects on
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Health Canada (2022) Caffeine in Foods, Canada.ca. Gouvernement du Canada. Available at: https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/food additives/caffeine-foods.html.
Jee, H. J., Lee, S. G., Bormate, K. J., & Jung, Y. S. (2020). Effect of Caffeine Consumption on the
Risk for Neurological and Psychiatric Disorders: Sex Differences in Human. Nutrients, 12(10), 3080.
Peerapen, P., & Thongboonkerd, V. (2018). Caffeine in Kidney Stone Disease: Risk or
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Schubert, M. M., Irwin, C., Seay, R. F., Clarke, H. E., Allegro, D., & Desbrow, B. (2017). Caffeine,
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Van Dam, R. M., Hu, F. B., & Willett, W. C. (2020). Coffee, Caffeine, and Health. The New England journal of medicine, 383(4), 369–378.