午夜福利1000集合

Coffee is no good for you 鈥� that鈥檚 the received wisdom, at least. It is full of caffeine that鈥檚 addictive and can make you bounce off the walls, give you headaches and disrupt sleep. Excessive consumption has been linked to heart disease and cancer. And although coffee increases alertness and focus, the effects are short-lived. Users quickly become tolerant: people who regularly drink coffee are no more alert on average than those who don鈥檛. For regulars, , bringing them back to a baseline level of alertness.

Sounds like one to avoid, then. But of the Northern Ireland Centre for Food and 午夜福利1000集合 in Coleraine, UK, thinks that鈥檚 overbrewed. 鈥淗aving looked into it, I don鈥檛 feel so bad having three or four cups of coffee a day,鈥� she says.

Pourshahidi has just carried out a , in work partly funded by the Italian coffee company Illycaff猫. For a start, she finds few grounds to suppose that imbibing a moderate amount of caffeine is harmful. For an addictive substance, caffeine is surprisingly easy to kick, too: simply getting people to is an effective strategy.

Beyond caffeine, coffee contains high levels of compounds called chlorogenic acids, known to . How this works isn鈥檛 clear, but it backs up the observation that coffee drinkers have a lower risk of type 2 diabetes.

On the other hand, two oily compounds in coffee, cafestol and kahweol, do seem to increase 鈥渂ad鈥� cholesterol that clogs blood vessels 鈥� but most coffee we drink, including instant, doesn鈥檛 contain much of either, says Pourshahidi. Espresso machines almost entirely get rid of them and French presses don鈥檛 do a bad job either. The thing to avoid is the boiled, unfiltered coffee popular in Turkey, Norway and Sweden.

Studies on coffee consumption and cancer typically find no correlation or a mildly beneficial effect, except among people who gulp down 40 or more cups a day and those who drink Turkish-style coffee. Even where coffee drinkers appear to be at greater risk than non-drinkers, the studies generally fail to show a proportional relationship between the amount consumed and risk, suggesting some other factor is involved 鈥� perhaps that people who drink coffee also drink more alcohol or smoke more, says Pourshahidi. Last June, the World 午夜福利1000集合 Organization changed its stance on coffee from 鈥減ossibly carcinogenic鈥� to 鈥�. The sole caveat was that any hot drink 鈥� above 70 掳C 鈥� increases the risk of oesophageal cancer.

鈥淐offee drinkers are no more alert on average than others鈥�

So enjoy the odd coffee, but do yourself a favour: let it cool.

Tea

Tea drinkers are often bathed in smug satisfaction: unlike coffee drinkers, their beverage of choice full of life-giving, leafy goodness. Much of the buzz centres on flavonols, with a particular focus on green tea and its most abundant flavonol, epigallocatechin-3-gallate (EGCG). It boasts antioxidant and anticancer effects, at least when added to cells in a dish.

Time to pour some cold water. Although some studies have found that drinking green tea (and to a lesser extent, black tea) lowers the risk of breast, gut and lung cancers, a 2009 review of 51 studies involving a total of 1.6 million people .

It is a similar equivocal story for other supposed benefits. Extracts of both green and black tea reduce blood sugar levels in diabetic rats and mice, and . Tea and its extracts may also , and animal studies suggest that catechins, compounds found in black tea, can inhibit enzymes that digest fat and starch and . Some or all of that might explain a small correlation between tea consumption and weight loss in overweight or obese people. So far so good, but the bad news is that the amount of weight lost was , and probably outweighed by other lifestyle choices.

Still, a nice cuppa is unlikely to do you much harm. One woman did lose all her teeth at 47 due to a fluoride overdose from tea, but she had been brewing up 100 to 150 teabags daily for 17 years. For most of us, tea鈥檚 fluoride content and anti-bacterial properties actually protect our gnashers. A study of tea鈥檚 potential as a mouthwash found that , and would probably work out cheaper. Black tea similarly fights cavities and .

This article appeared in print under the headline 鈥淐offee鈥�