![]() Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. And while the effects of caffeine on reproductive health and the metabolism – obesity, blood pressure, diabetes – have been investigated, there appears to be little evidence that moderate caffeine consumption can cause far-reaching ill effects.Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: Identical results were seen irrespective of whether those studied drank coffee, an energy drink, took a caffeine pill or ate food with a high caffeine content. For people working overnight, consuming caffeine had a similar effect to taking a power nap. Researchers at London's School of Hygiene and Tropical Medicine published evidence earlier this month that showed caffeine helped improve workers' memory and concentration. Indeed, ingesting significant quantities of caffeine may result in fewer errors, injuries and accidents at work and in leisure time. However, long-term, habitual consumption could lead to better mental functioning in old age. Research suggests that sensitive groups, such as children, could experience ill-effects from high-caffeine energy drinks (though much more research is needed to produce conclusive evidence). Over 2,000 articles have appeared in scientific journals the last two years alone. The effects of caffeine have been exhaustively studied. Caffeine intake is normally highest when alertness is reduced – early in the morning, after prolonged work or after lunch – and is reduced at times when high alertness is undesirable e.g. However, most people can control their caffeine consumption, limiting its interference with the natural process that tries to keep us awake. Different people have different sensitivities: for some even small amounts can cause adverse reactions. An excessive amount is around 500mg a day, which can cause health problems, such as anxiety. The average intake in the Western world is around 200mg a day. Recent studies have linked smoking to high caffeine intake, citing this swift reduction in levels as one of the main reasons.ĭaily caffeine intake varies between cultures and countries. Caffeine half-life in women on the pill is around 11 hours, and in smokers it decreases to three. This is because unborn babies can only metabolise it very slowly. In pregnant women the half-life can increase to 18 hours. Its half-life – the time it takes for its level to halve – is between five and six hours. The amount of caffeine peaks in the bloodstream between 15 and 45 minutes after ingestion. This process is known as "competitive inhibition" and effectively delays the onset of fatigue, increases alertness and improves people's ability to sustain attention. However by doing so they take the place of adenosine molecules that could make a difference. Caffeine molecules bind to these receptor cells but have no active effect on the nervous system. There is also evidence to suggest that it decreases blood flow in the brain. (A study published by Bristol University last week argued that caffeine can't make irregular users more alert a cup of coffee in the morning, the research suggested, only counteracts the effects of withdrawal that have built up overnight.)Īdenosine bonds to receptor cells in the brain to calm the activity of the central nervous system, thus triggering tiredness. Doctors say at least 100mg is necessary to properly increase our alertness. Meanwhile, a 12oz serving of cola contains just 40mg. The same sized serving of tea holds 35-45mg. For the record, in a 5oz cup of filter coffee, there is between 100mg and 150mg of caffeine. While tea naturally has more caffeine gramme for gramme than coffee, there is less tea per cubic centimetre of cup, leading to its weaker stimulant properties. The exact amount of caffeine present in a drink depends on its growing conditions and preparation. Coffee-quaffing originated in Yemen in the 15th century. The earliest recorded caffeine consumers were in China in the 10th century BC, when philosophers believed tea-drinking was "an indispensable ingredient to the elixir of life".
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