Caffeine has been a topic of health debates for decades. Proponents cite both nutraceutical and functional benefits while opponents sound warnings about negative health effects. As with all controversial issues, the answer is most likely individual and hinges upon each person’s unique biochemical, genetic, and environmental makeup. One man’s cuppa friend may be another’s foe.
Without question, caffeine (1,3,7-trimethylxanthine) is the most widely consumed stimulant in the world. In the United States alone, close to 90 percent of all adults consume an average of 200mg of caffeine daily, most commonly in the form of coffee. Pharmacologically, caffeine is an adenosine receptor antagonist, acting primarily on A1 and A2A receptors, which control functions of the brain associated with sleep, arousal, and cognition. What’s more, caffeine is rather quick-acting. It is quickly absorbed by the stomach and small intestine, with peak plasma levels occurring in the first 30 minutes and a half-life ranging from 2 to 10 hours. Caffeine tolerance and a genetic predisposition to faster or slower clearance influence both the degree and length of its effects. It’s also important to note that in the case of coffee, the presence of more than 1000 different compounds including phenolics, diterpenes, and melanoidins, also interact with caffeine to influence behavior both directly or indirectly.
Sleep deprivation is the chief complaint against caffeine consumption and may present a valid reason for most individuals to limit their intake to the early daytime hours. Daytime caffeine consumption causes a reduction in 6-sulfatoxymelatonin (the main metabolite of melatonin) that may persist into the evening and nighttime hours. Since sleep deprivation is a common health problem among Americans (who already average fewer than 6 hours of sleep a night), leading to significant reductions in cognitive function, awareness, focus, memory, attention and response time, opponents of caffeine consumption may have a valid argument on this front.
On the other side of the fence, caffeine has been cited as an excellent nutraceutical for enhancing cognitive health and function as well as guarding against the effects of age-related cognitive decline. In a randomized, double-blind placebo-controlled counterbalanced-crossover study, the effects of regular coffee (containing 100mg of caffeine), decaffeinated coffee (containing ~5mg of caffeine), and placebo on measures of cognition and mood were determined in 59 subjects. Regular coffee consumption resulted in faster responses during digit vigilance and rapid visual information processing tasks, higher ratings of alertness and overall mood, lower mental fatigue ratings, and lower tiredness and headache ratings.
So how can caffeine both promote and stifle cognitive function? Perhaps it boils down (no pun intended) to the timing of caffeine consumption and the form of caffeine consumed; namely, coffee’s additional components may enhance its benefits.
Or perhaps caffeine should be viewed as a therapeutic medium for specific cognitive deficiencies, rather than a recreational compound. Alzheimer’s disease (AD) is the most common neurodegenerative disorder in elderly people and caffeine’s ability to modulate the adenosinergic system has allowed it to become a viable therapy for AD. Further, epidemiological evidence supports a role for the habitual consumption of caffeine in reducing risk for AD and associated cognitive decline. In 2002, a retrospective study supported an inverse correlation between caffeine intake and age at AD onset after other common risk factors were accounted for. Patients with AD had an average daily caffeine intake of 73.9 +/- 97.9 mg during the 20 years that preceded diagnosis, whereas the controls had an average daily caffeine intake of 198.7 +/- 135.7 mg during the corresponding 20 years of their lifetimes. Several other cross-sectional and longitudinal population-based studies suggest a protective effect of caffeine use against late-life cognitive impairment/decline.
While a firm verdict cannot be reached regarding the benefits and risks of caffeine consumption, it is clearly beneficial in some cases for promoting cognitive health and perhaps even reducing the risks of age-related dementia. However, these benefits must be viewed in light of adequate sleep, which is equally (if not more) important for cognitive health and function. For the majority of us, a morning cup of joe is still most likely a healthy habit, as long as the cup isn’t refilled numerous times later in the day.