TUESDAY, Nov. 8, 2005 (HealthDay News) -- Women who love drinking coffee can keep on loving it, researchers say.
Too bad the same isn't true for those who can't get enough of caffeinated colas, however.
A new study has found that regular coffee drinking has no links to temporary hypertension or persistent high blood pressure.
In fact, women who consume the most coffee may even get a protective cardiovascular effect from their cup of java.
In contrast, drinking caffeinated sugared or diet colas raise blood pressure, the researchers found.
"This is good news for women who enjoy drinking coffee," said study author Dr. Wolfgang Winkelmayer, a researcher in the divisions of pharmacoepidemiology and pharmacoeconomics at Brigham and Women's Hospital in Boston. "Quite contrary to popular belief, it appears to not increase the risk of high blood pressure."
The findings appear in the Nov. 9 issue of the Journal of the American Medical Association.
Some 50 million Americans have hypertension or persistent high blood pressure, a major risk factor for coronary heart disease, stroke and congestive heart failure.
"There is clearly a lot of public belief and clinical lore among physicians that coffee increases blood pressure," Winkelmayer said.
Most of the studies that have been done, however, are short-term and there is some evidence the effect may taper off over time.
"There has never been very good evidence that caffeine is a precipitant in chronic hypertension," said Dr. Nieca Goldberg, chief of women's cardiac care at Lenox Hill Hospital in New York City.
The authors of this study looked at information on nearly 156,000 American women who participated in the Nurses' Health Studies I and II and who did not have diagnosed hypertension at the start of the study. Participants filled out questionnaires on caffeine consumption and were followed over a dozen years.
Contrary to expectations, the authors found no association between caffeine intake and hypertension.
They did find one surprise, however: Women who consumed either the least caffeine or the most caffeine were at lowest risk of developing high blood pressure.
"We took a step back and deconstructed this, given that total caffeine intake is just an aggregate of individual consumption of regular and decaffeinated coffee, regular and decaffeinated tea and sugared and diet cola," Winkelmayer said.
That analysis showed that coffee drinking may even have a protective effect on blood pressure. The results for caffeinated tea were inconclusive.
But caffeinated cola beverages, whether sugared or diet, were linked with an increased risk of high blood pressure.
Younger women who drank four or more cans or glasses of caffeinated, sugared cola each day were at a 28 percent increased risk of hypertension compared with women who drank less than one can or glass a day. Younger women who drank higher amounts of diet cola were at a 19 percent increased risk.
Older women who drank four or more cans or glasses of caffeinated, sugared cola each day were at a 44 percent increased risk of hypertension, while those that drank the same amount of diet soda faced a 16 percent elevated risk.
"We found a very clear direct association between cola consumption, whether sugared or diet, and an increased risk of high blood pressure," Winkelmayer said.
It's not clear why this is so, although caffeine is obviously not the culprit. Additional analyses seemed to exonerate sodium, magnesium, potassium and calcium as well.
"At the end of the day, we do not have much of an idea of what might cause this association. It needs to be confirmed and we need to find the biological link," Winkelmayer said.
For the time being, it's not enough reason to kick the cola habit. "Would I go as far as recommending that women reduce their soda or cola intake? Maybe not," Winkelmayer said. "This is the first study that has shown this association."
And, Goldberg pointed out, there may be other reasons to avoid caffeine besides high blood pressure.
"Caffeine can precipitate palpitations in people who are sensitive," she said. "We have to remember that there are some non-obvious sources of caffeine, for example, dark chocolate, which everyone thinks is good for heart."
More information
For more on hypertension, head to the American Heart Association.
