Michele McDonald/for The Boston Globe
Coffee, it seems, has gotten a bad rap -- blamed for heart problems, higher cholesterol, and hyperactivity. Now many researchers believe that not only is coffee not harmful, but it should be put in the category of health food. A study published Thursday in the journal Stroke finds that drinking coffee lowers stroke risk in women by 22 to 25 percent over a decade.
Perhaps it's time for coffee to push aside green tea. "I think it's actually more healthful than tea," contends Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health. As an investigator on the Harvard Nurses' Health Study, Hu should know. He's identified a connection between coffee consumption and lower diabetes risk.
In recent years, coffee drinkers have been found to have a reduced risk of gallstones, colon cancer, liver disease, and Parkinson's. Long-distance athletes also have increased endurance if they drink coffee before a race.
Whether caffeinated coffee is safe to have during pregnancy remains uncertain, though the latest research indicates that drinking as little as 200 milligrams of caffeine a day -- equivalent to two cups of brewed coffee -- doubles the rate of miscarriages. "The general consensus is that pregnant women should have less than this amount," says Joan Salge Blake, a registered dietitian at Boston University.
And it's probably a good idea for nursing mothers to stick to a limit of one or two cups a day as well, since excessive amounts of caffeine can pass into breast milk and cause behavioral changes in the baby.
But what about the rest of us?
The Swedish researchers who conducted the stroke study -- in which nearly 35,000 women were followed for a decade after reporting their coffee intake on a 1997 dietary survey -- say people shouldn't take up a coffee habit based on these results. But, they add, the finding should ease concerns of those who fear that coffee drinking is harmful.
Women in the study who drank as little as one cup a day to more than five cups a day had a lower stroke risk than those who drank none. Oddly, it didn't show that drinking four or five cups a day offered any greater protection than drinking just one, which raises some doubt about the strength of the finding.
"Other studies have found a dose-response relationship" for other health effects, says Hu. His own diabetes research found that drinking three to four cups of coffee a day lowers the risk of Type 2 diabetes by 20 percent and that drinking five or more cups lowers risk by 30 percent.
"There's still not enough data to make recommendations on how much people should drink," Hu says. "It's really an individual choice." But he does believe that the preponderance of evidence is strong enough to deem coffee a health food, that is, if it's not topped with whipped cream or blended with loads of sugar, chocolate or caramel syrup.
Just how java delivers its nutritional benefits remains largely unknown, but it could be the significant amount of antioxidants and other disease-fighting chemicals contained in the coffee bean. These may lower levels of dangerous inflammation and may improve the action of the hormone insulin.
Also not known: Whether decaffeinated coffee offers the same benefits. "Several studies suggest that," says Hu, "but the evidence is limited."
That's an important question to have answered because some people simply can't tolerate caffeine. "They get jittery, have increased anxiety, or can't sleep at night, even if they only drink coffee in the morning," says Blake. Those folks should stick with decaf.
Experts are also wary about recommending coffee for teens. "They need to be getting a good night's sleep and not be wired," Blake says. Hu agrees, adding that children can be extra sensitive to caffeine to the point that moderate amounts can affect their mood and behavior.
June 6, 2011
By Deborah Kotz, Globe Staff Bean sprouts are likely to blame for the E. coli outbreak in Germany …
June 4, 2011
By Carolyn Y. Johnson, Globe Staff A drug that blocks production of the hormone estrogen cut breast …
June 10, 2011
By Deborah Kotz, Globe Staff Quick quiz: What's the most dangerous spot in the house? Sure, kitche …
June 9, 2011
By Elizabeth Comeau, Boston.com Staff loading video... (please wait a moment)Requires Adobe Flash …
May 16, 2011
By Deborah Kotz, Globe Staff No question, most of us sit way too much, and that's not good for our …
April 26, 2011
By Elizabeth Comeau, Boston.com Staff Last week, I asked you how you find the time to stay …
June 10, 2011
Greene, Bill Globe Staff/The Boston Globe By Deborah Kotz, Globe Staff I was bummed to hear th …
June 6, 2011
By Deborah Kotz, Globe Staff A new research finding could help parents and public health specialis …