A recent issue of the journal of nutrition includes a detailed literate review of the effects of caffeine consumption on performance and health. As an ingredient that has often been demonized, they uncovers the large body of evidence describing the beneficial effects of human caffeine consumption on a number of physiologic systems.
They explored data on the effects of caffeine outside of its usually considered role as a stimulant. They outlined the effects of caffeine on 24-hours energy expenditure, sleeping metabolic rate and fat lipolysis, concluding that the ingestion of as little as 50mg of caffeine by a normal -weight, healthy man produced a significant rise in metabolism within 30 minutes of caffeine ingestion, persisting for at least four hours and producing a significant six per cent total increase in daily resting energy expenditure. Also increasing the firing of skeletal muscle motor units and enhancing cognitive function, they highlighted the role that caffeine can play in preventing fatigue. Moderate caffeine consumption (200mg) was concluded to increase neuromuscular coordination in normal and sleep-deprived conditions and even to improve mood, self-image and also relieve anxiety.
They also highlighted the safety of moderate intakes of caffeine in healthy individuals with detailed review of the published literature, with studies indicating that intakes of up to 40mg per day reduced risk of death in the elderly by 10 per cent. Interestingly, although retrospective case control studies tend to support the theory that the risk of developing coronary heart disease (CHD) is associated with an intakes of three or more cups of coffee per day (360 mg per day), more reliable prospective studies have consistently found no association between coffee consumption and CHD, a fact that has not been relayed much in the general press. Caffeine has been shown in large single doses (300mg) to increase blood pressure but only transiently, and this increase is not seen with habitual intakes. They pointed out that caffeine should still be avoided by people with pre-existing high blood pressure, heart disease or diabetes and pregnant women.
The Upshot is that if you do not have a history of heart disease, high blood pressure, diabetes or are pregnant, habitual intakes of up to 400mg of caffeine per day are associated with many benefits that could positively affect performance and health. Rather than giving the green light to going caffeine mad, this evidence should rather outline what level of caffeine might be beneficial. If you are having three four cups of coffee per day or using a couple of caffeinated gets on the bike this, it seems is unlikely to have any negative effects and could well improve your performance and wellbeing.