You thought coffee was bad for you? Actually, it seems to protect against all sorts of ills, from diabetes to liver cancer
Every passing week brings news for latte lovers, and the latest on coffee is the best buzz yet. It turns out that a cup of joe--or a carafe--may chase away the blues; turn you into a better athlete; and protect against diabetes, Parkinson's disease, gallstones, and some cancers. Last week's headline: Researchers at the National Institute of Diabetes and Digestive and Kidney Diseases found that a two-cup-a-day habit can dramatically cut the risk of chronic liver disease in those at greatest risk. "If its benefits continue to mount, coffee may come to be viewed as a health food," says Lona Sandon, a registered dietitian and spokesperson for the American Dietetic Association.
This is quite a turnaround from the not-so-distant past, when the brew was blamed for a host of ills ranging from pancreatic cancer and fibrocystic breasts to fatal heart arrhythmias and elevated cholesterol. What has made nutrition experts rethink the pros and cons? Worrisome preliminary findings have been refuted by bigger, more rigorous studies. "A lot of early research was flawed," says Manfred Kroger, a now retired food scientist from Pennsylvania State University who has long been tracking it. "Coffee lovers are more likely to do harmful things like smoke and drink alcohol in excess, so coffee was often falsely incriminated."
The health benefits of coffee are not so thoroughly proven yet that anyone is suggesting actually upping your intake. Nor is anyone saying coffee is entirely benign. Pregnant women are still advised to abstain, since there's a concern that more than a couple of cups a day may trigger a miscarriage. Too much caffeine can upset some stomachs, exacerbate heartburn, and make people too jittery--or sleepless. But "if you're already drinking five or six cups a day, I'd be hard pressed to come up with a reason you should cut back," says Walter Willett, chairman of the department of nutrition at Harvard School of Public Health and a leading investigator of coffee. (If you load them with whipped cream and sugar, however, you invite an expanded waistline and other health problems.)
Nutrition experts like Willett point out that, like tea, coffee is rich in antioxidants--substances in vegetables and fruits that deactivate disease-causing byproducts of the body's metabolism. "Coffee is by far the largest source of antioxidants in our diet," says Joe Vinson, a chemistry professor at the University of Scranton in Pennsylvania. That's not just because we drink so much. In tests conducted at Vinson's lab, coffee topped the list of foods that are densest in antioxidants, surpassing blueberries, broccoli, and most other produce. Only chocolate, dried fruits, and dried beans ranked higher.
Wired brains. Much-maligned caffeine appears to be a protective substance, too. Beyond waking up sluggish minds, caffeine may serve as a mild antidepressant--or so researchers theorize. One Harvard study of 80,000 American women found that those who drank more than two or three cups of regular coffee daily cut their risk of suicide over 10 years by one third. And the stimulant has been shown in animal experiments to inhibit the brain-cell destruction that occurs in Parkinson's disease. A 30-year study in Hawaii of 8,000 Japanese-American men found that coffee consumers were about 48 percent to 84 percent less likely to be diagnosed with Parkinson's. Another study on the mainland yielded similar findings and traced the protective effect to caffeine in coffee, tea, and colas.
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.
Other charges against coffee have also failed to stick. Studies examining the relationship between caffeine and fibrocystic breasts have failed to establish that there is one--and experts say there's no evidence coffee causes breast cancer. Any connection to pancreatic cancer has been found to be weak to nonexistent. Links to osteoporosis--based on the observation that drinkers excrete more calcium in their urine--are also tentative at best. And getting the recommended daily allotment of calcium seems to cancel out any increased risk, says Bess Dawson-Hughes, director of the bone metabolism lab at Tufts University.
As for the oft-repeated warning that coffee dehydrates: It, too, is a myth. Like any fluid, coffee may send its fans to the bathroom frequently. But a major report issued last year by the U.S. government's Institute of Medicine concludes that the beverage quenches thirst as effectively as water and does not deplete body fluids.
Is it addictive? Indeed, quitting cold turkey can cause such withdrawal symptoms as headaches or grumpiness--assuming you can withdraw. Now, you don't need to.
This story appears in the December 19, 2005 print edition of U.S. News & World Report.