You thought coffee was bad for you? Actually, it seems to protect against all sorts of ills, from diabetes to liver cancer
Elsewhere in the body, caffeine reduces muscle fatigue and boosts speed and endurance--the reason athletes have long turned to it for a competitive edge. Sports physiologists attribute caffeine's potency to its ability to trigger the release of adrenaline, which in turn strengthens muscle contractions and fosters the creation of energy from fatty acids. In the gall bladder, caffeine also promotes contractions--which scientists suspect may explain why routine drinkers have fewer gallstones.
Other benefits attributed to coffee are harder to pin on any one ingredient. American, Finnish, and Swedish studies all suggest that both decaffeinated and regular coffee reduce the risk of type 2 diabetes. There's a clear "dose-response" relationship: The more you drink, the safer you are. Those who downed five or more cups a day slashed their risk by at least half. Potassium, niacin, magnesium, chlorogenic acids, and tocopherols are just some of the nutrients in coffee that scientists suspect may counter the risk of diabetes.
Researchers don't know exactly why coffee appears to thwart certain cancers, either. In Japan, where liver cancer is a major killer, a recent study of 90,000 men found that those with a coffee habit are half as likely as nonimbibers to develop the disease. Last week's report on coffee and the liver, published in the journal Gastroenterology , offers a possible connection: The researchers found that people who are overweight or who overindulge in alcohol are half as likely to suffer from cirrhosis and other forms of chronic liver disease--leading risk factors for liver cancer--if they drink as little as two cups of coffee a day, compared with people who drink less than a cup. High coffee consumption has also been linked to a lower incidence of bladder cancer in heavy smokers. Some research points to antioxidants as the most likely cancer-fighting agents in coffee; other research indicates caffeine may be the protective ingredient.
What of old fears that coffee promotes heart disease? The largest and longest studies both here and abroad consistently suggest that coffee has no bad cardiovascular effects--even at six-plus cups a day.
It is true that coffee contains a fatlike chemical, cafestol, known to raise cholesterol levels. But cafestol is mainly found in coffee made by the European method of boiling ground beans in water or the related "French press" method. Percolated or filtered coffee, favored by most Americans, removes the offending agent and does not hike cholesterol. (A word of caution: Decaf coffee may be an exception to this rule. A recent Stanford study found that even consumers of filtered decaf had modestly higher levels of fatty acids and other precursors of LDL, or bad cholesterol.)
Take heart. A transient rise in blood pressure may also be seen in occasional coffee drinkers. "But regular consumers build up tolerance and are largely immune to this effect," says Donald Hensrud, associate professor of preventive medicine and nutrition at the Mayo Clinic College of Medicine in Rochester, Minn. Reassuringly, two new studies of nurses in the United States actually show the biggest guzzlers to be at slightly lower risk of hypertension. And while overdoing it may occasionally provoke heart palpitations, these appear to be harmless, reports Harvard's Willett. There's no evidence, he says, that coffee sparks fatal arrhythmias.