Coffee drinkers can take heart from a series of studies presented this week at American Heart Association conferences in San Francisco.
For example, coffee drinkers appear to have a lower risk of hospitalization for abnormal heart rhythms. And there's no indication that having a few cups every day increases the risk of atherosclerosis, the thickening of blood vessel walls that can lead to heart attacks and other problems. What's more, something in coffee other than caffeine might be responsible for a reduced risk of diabetes for women who regularly imbibe java.
Not every report at the AHA's annual conferences on Cardiovascular Disease Epidemiology and Prevention and Nutrition, Physical Activity and Metabolism was totally upbeat for coffee lovers. One report did find a potential link between coffee drinking and high blood pressure, but the effect was described as "modest." And, like the other studies, it came hedged with the caveat that the finding wasn't based on a controlled trial -- the gold standard for assessing risk and benefit -- but from observational studies, which don't exclude all possible factors.
The heart rhythm research looked at the rate at which 130,054 members of the Kaiser Permanente Medical Care Program were hospitalized for heart rhythm disturbances. About 2 percent of them had hospital stays because of such abnormalities, the most common being atrial fibrillation. But the risk was 18 percent lower for those who reported drinking four or more cups of coffee a day, compared to those who didn't drink coffee, said Dr. Arthur Klatsky, a senior consultant in cardiology for the program, who led the study.
"It might be a surprise, because coffee does give some people the jitters," Klatsky said. "And I don't think we're ready to tell people they should drink coffee to prevent heart rhythm problems."
The study didn't offer any reason why coffee might reduce heart rhythm problems, Klatsky said. "It could be that coffee drinkers have better diets or exercise more. We can't say for sure that it might not be related to minor heart rhythm problems that don't require hospitalization."
The bottom line: "Coffee drinkers don't have to quit because they have heart rhythm problems," Klatsky said. "That's about as far as we can go."
Another study that has followed more than 3,000 men and women for 20 years found no association between coffee consumption and atherosclerosis for just about every demographic group -- men and women, blacks and whites, smokers and nonsmokers. Participants in the study included people whose coffee consumption ranged from none to more than four cups a day.
"Based on these data, there does not appear to be any substantial association between coffee drinking and increased or decreased odds of developing atherosclerosis or its progression over time," study leader Jared Reis, an epidemiologist with the U.S. National Heart, Lung, and Blood Institute, said in a prepared statement.
The third study, based on a report from the long-running Women's Health Study, provided a possible explanation for a lower incidence of type 2 diabetes -- the kind that generally develops later in life -- among coffee drinkers. Researchers compared 359 post-menopausal women newly diagnosed with type 2 diabetes and 359 women without the disease. They found that women who drank four or more cups of caffeinated coffee a day had a 56 percent lower risk of developing the condition than those who did not drink coffee.
That reduced risk appears to be due to the effects of caffeine on a protein that binds to sex hormones, said Dr. Atsushi Goto, of the University of California, Los Angeles, who presented the report. But the finding is preliminary and requires further study, Goto added.
The report linking consumption of one to three cups of coffee a day with a slightly increased risk of high blood pressure came from Dr. Liwei Chen, assistant professor of epidemiology at the Louisiana State University School of Public Health, using data from six studies that included more than 172,000 participants.
"Based on our results, long-term coffee drinking might be a risk factor for hypertension, but the effect is very moderate," Chen said. "We definitely need more research and evidence to clarify our findings based on the meta-analysis of published prospective studies. Meanwhile, I think it is important for people to consider lowering their coffee drinking if they are concerned about their blood pressure."