March 5, 2010
Dear Mayo Clinic:
What are the current thoughts on coffee as to how it affects one's health, good or bad?
Over the past several years, research has busted some health myths about coffee. It doesn't contribute to heart attacks, cancer or reduced bone density — all of which have been suspected in the past.
We've learned that coffee, in moderation — perhaps 1 to 2 cups daily — isn't bad for you. And in some cases, coffee seems to offer health benefits, perhaps the most noteworthy being a reduction in the risk of type 2 diabetes.
Many studies have shown that coffee decreases the risk of type 2 diabetes. One study, published in the Annals of Internal Medicine in 2004, showed this significant protective effect increased with coffee consumption up to 6 cups a day. The effect was similar for caffeinated and decaffeinated coffee.
This study and others on the health effects of coffee highlight that there's more to coffee than caffeine. Where health benefits or risks have been documented, researchers don't necessarily know what components in coffee are linked to the health effects. A "cup of joe" has up to 2,000 different components, including micronutrients such as magnesium, potassium, niacin and vitamin E. Among coffee drinkers, coffee may be the largest food source of antioxidants — substances that protect cells from the damage caused by unstable molecules called free radicals.
Studies have documented coffee's other health benefits in various areas:
Parkinson's disease: A number of studies have shown that coffee drinkers benefit from a protective effect against Parkinson's disease.
Asthma: Coffee may reduce asthma symptoms.
Gallstones: Coffee may reduce gallstone formation.
Cognition: Coffee increases alertness. That's why it's the morning wake-up call for many people. Studies also have shown that coffee can improve cognitive performance. Results from at least four studies suggest that coffee drinkers have a decreased risk of Alzheimer's disease.
Mental health: Three studies have shown a decreased risk of suicide with moderate coffee consumption. The reason for this isn't clear.
Liver disease: Coffee seems to offer a protective effect against liver disease including cancer, especially among those who drink alcohol.
Before you rush to brew a pot of coffee, know that there are some side effects and potential health concerns from drinking coffee. Side effects can include jitteriness, insomnia and benign heart palpitations. The extent of the side effects varies by individual and the ability to metabolize caffeine. Some people forgo coffee in the afternoon because it causes insomnia. Others can have a coffee nightcap and sleep soundly.
Side effects also can include loose stools and heartburn or reflux in people who are predisposed to those conditions. Coffee may worsen urinary symptoms for men with prostate problems.
Occasional coffee drinkers may see an increase in their blood pressure after a cup of coffee. With regular consumption, tolerance develops and the blood pressure falls to previous levels. If you are going to drink coffee, it's probably best to enjoy it daily to avoid blood pressure spikes.
Here's another reason for consistency. If you skip a day, you're likely to experience a withdrawal headache, since caffeine is slightly addictive.
Another health concern is that coffee in more than moderate amounts may affect a woman's fertility and possibly contribute to miscarriage. Other negatives are that coffee decreases iron and calcium absorption. It also increases urinary calcium loss, but this can be offset by increasing calcium consumption.
If you are not a coffee drinker, I wouldn't suggest starting for the sake of better health. On the other hand, if you enjoy a daily cup or two of coffee and aren't bothered by side effects, there's no need to worry about serious health risks from coffee. And you may be sipping in some health benefits, too.
— Donald Hensrud, M.D., Preventive and Internal Medicine, Mayo Clinic, Rochester, Minn.