The impact of caffeine on mood, cognitive function, performance and hydration: a review of benefits and risks

Abstract

The reputed benefits of moderate caffeine consumption include improvements in physical endurance, cognitive function, particularly alertness and vigilance, mood and perception of fatigue. In contrast, there are concerns that excessive intakes increase the risks of dehydration, anxiety, headache and sleep disturbances. This paper is a review of double-blind, placebo-controlled trials published over the past 15 years to establish what range of caffeine consumption would maximise benefits and minimise risks for cognitive function, mood, physical performance and hydration. Of the 41 human studies meeting the inclusion criteria, the majority reported benefits associated with low to moderate caffeine intakes (37.5 to 450 mg per day). The available studies on hydration found that caffeine intakes up to 400 mg per day did not produce dehydration, even in subjects undergoing exercise testing. It was concluded that the range of caffeine intake that appeared to maximise benefit and minimise risk is 38 to 400 mg per day, equating to 1 to 8 cups of tea per day, or 0.3 to 4 cups of brewed coffee per day. The limitations of the current evidence base are discussed.

Is Caffeine a Cognitive Enhancer?

“…The effects of caffeine on attention and psychomotor performance have been extensively reviewed (for review see [20,54,[56][57][58][59]65]). Not all studies found effects of caffeine on the two variables, although most studies found improvements in reaction time.…”

“…At low doses, caffeine improves hedonic tone and reduces anxiety, while at high doses there is an increase in tense arousal, including anxiety, nervousness, and jitteriness. Caffeine improves concentration and help to focus mainly by eliminating distractors (for review see [2,[54][55][56][57][58][59][60]). …”

Efeito da ingestão de cafeína em diferentes tarefas de tempo de reação

“…No entanto, alguns estudos experimentais têm mostrado que indivíduos moderados e não habituados ao consumo de cafeína, independente da retirada, obtiveram melhoras no desempenho psicomotor (SMITH;SUTHERLAND;CHRISTOPHER, 2005;CHILDS;WIT, 2006). Portanto, Ruxton (2008) afirma que devemos levar em conta um possível efeito da abstinência, pois Heatherley et al (2005) constataram em seu estudo que, após 8 horas de abstinência, a ingestão de 1,2mg/kg de cafeína produziu efeitos positivos no desempenho psicomotor em consumidores habituados a cafeína, contudo, em intervalos menores o efeito é menor. Ainda assim, de acordo com os estudos citados acima, os efeitos da cafeína no desempenho cognitivo ocorrem mesmo sem a sua retirada.…”

Composition and Health Properties of Coffee Bean

“…The average content of caffeine of green coffee bean from Brazil, Colombia, Ethiopia and Kenya between 4.36 mg/g dw to 4.99 mg/g dw [23], specifically green coffee bean from Ethiopia is around 1.01 (w/w%) to 1.19 (w/w%) [24]. Intake of 38mg to 400 mg per day of caffeine equal to 0.3 to 4 cups of brewed coffee per day could minimize risk and maximize the benefit of caffeine intake [25]. …”