A visitor drinks coffee at the 'International Coffee Festival 2007' in the southern
Indian city of Bangalore February 25, 2007. [Reuters]

Because the caffeine in coffee and other foods can cause a short-term spike in blood pressure, there's been concern that coffee drinking may over time raise the risk of high blood pressure. Studies, however, have come to inconsistent conclusions.

In the new study, published in the American Journal of Clinical Nutrition, researchers found that healthy women who drank upwards of six cups of coffee per day were no more likely than abstainers to develop high blood pressure over the next decade.

On the other hand, women who drank coffee occasionally or in moderation -- reporting anywhere from zero to three cups a day -- had a higher risk of developing high blood pressure than the heavy coffee drinkers or the abstainers.

For men, the risk of high blood pressure did not significantly increase or decrease, regardless of how much coffee they drank each day. However, men who abstained did have a lower risk than any coffee drinkers.

Still, the effect was "relatively small," Dr. Cuno S. P. M. Uiterwaal, the study's lead author, told Reuters Health.

Handing out blanket advice on coffee or any food is difficult, noted Uiterwaal, an associate professor at the University Medical Center Utrecht, in the Netherlands.

But given the overall research on the effects of coffee on healthy people -- including studies that suggest health benefits, like a lower diabetes risk -- there seems to be no reason to discourage them from enjoying their java, according to the researcher.

"The general advice to healthy people, if any, would then be that there is no argument for healthcare workers to advise against coffee drinking," he said.

The findings come from an 11-year follow-up of nearly 6,400 Dutch men and women who were 40 years old, on average, at the study's start. Participants completed detailed questionnaires on their diets, including coffee drinking, as well as other lifestyle habits, education and family medical history.

Over the next 11 years, the researchers found, light coffee drinkers were more likely to develop high blood pressure than either non-drinkers or heavier consumers, with other health factors considered.

A possible reason, according to Uiterwaal's team, is that people who drink several cups of coffee every day develop a tolerance to the transient blood-pressure-raising effects of caffeine, while those who drink less coffee less often may remain sensitive.

Even if coffee drinking contributes to blood pressure elevations in some people, Uiterwaal noted, studies have failed to show that it actually raises the risk of heart disease in healthy people.

He also stressed, however, that this study focused on adults in good general health. The findings do not pertain to people with high blood pressure or other risk factors that increase their odds of heart disease.