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  • Cameron M. Clark

Coffee, Tea, Caffeine, and Cognitive Health

Coffee and tea are certainly two of the most popular beverages in the world, which makes its active ingredient, caffeine, the most widely consumed psychoactive agent. And with good reason. In addition to providing that often much-needed kick of morning energy, coffee and caffeine have been associated with some fairly impressive health benefits in recent research.

If you’re already a dyed in the wool coffee or tea drinker, it will come as no surprise to you that moderate doses of caffeine (40-300mg) have been associated with reduced fatigue, increased alertness, quickened reaction times, and even increased attentiveness during tasks that provide little stimulation. For reference, a typical 250ml cup of coffee might have around 100mg of caffeine, whereas the same volume of black tea may have around 50mg. Aside from these impressive (and perhaps familiar) immediate effects, caffeine consumption has also been associated with protective effects against depression, suicide, Parkinson’s disease, and even all-cause mortality (death from any cause). Unfortunately however, coffee has not been shown to protect against Alzheimer’s disease, or dementia more broadly.

Despite its health benefits, there is such a thing as ‘too much coffee’. Yes, it’s true – too much caffeine later in the day can cause difficulties with sleep, both in terms of falling asleep quickly, and the quality of your sleep. As former US president Ronald Reagan said “I never have coffee at lunch, I find it keeps me awake in the afternoon”. But even worse, high levels of caffeine intake can cause anxiety, restlessness, nervousness, dysphoria (feeling uneasy or vaguely dissatisfied), and “rambling flow of thought and speech” – essentially the opposite of sharp thinking!

So, drink your coffee or tea early in the day for those immediate benefits of mental clarity and alertness, as well as for the long-term protective effects from chronic diseases. The current science recommends staying below around 400mg per day, or roughly three to five cups of coffee. If you notice any negative effects associated with too much caffeine, consider cutting back to keep your mind clear, and your thinking sharp.


Dam, R. M. V., Hu, F. B., & Willett, W. C. (2020). Coffee, Caffeine, and Health. New England Journal of Medicine, 383(4), 369–378.



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