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NEW YORK (Reuters Health) - Sweet drinks have been linked to a slightly higher risk of developing high blood pressure, but, contrary to earlier research, a large new study finds that fruit sugar in those drinks is not the likely culprit behind that association.
Following more than 200,000 men and women for up to 38 years, researchers found that regularly consuming sweetened drinks -- either containing sugars or artificially sweetened -- was associated with a rise of about 13 percent in the risk of developing high blood pressure.
Carbonated and cola drinks were most strongly linked to risk for hypertension, but fructose in drinks did not stand out as a driving factor, the group reports in the Journal of General Internal Medicine.
High consumption of fructose from foods, such as fresh fruits, was tied to lower odds of developing blood pressure problems.
"We don't know what causes the increased risk in artificial- or sugar-sweetened beverages," said Dr. Lisa Cohen, lead author of the study and a researcher at the University of Maryland Medical Center.
"It's hard to say that from the fructose itself you're increasing your hypertension risk," she added.
Dr. Richard Johnson, a professor at the University of Colorado, Denver, who was not involved in the study, said the results are not enough to let fructose off the hook.
Work by Johnson and others has implicated fructose as a factor related to the risk of high blood pressure (see Reuters Health story of July 1, 2010).
Earlier studies, however, have only taken a snapshot in time, Cohen said, and could not determine which came first -- the high blood pressure or the taste for sweet drinks.
Cohen and her colleagues looked at data from three massive studies, including nearly 224,000 healthcare workers, whose diet and health were tracked for 16 to 38 years.
No participants had diagnosed high blood pressure at the beginning of the study period.
Over time, those who drank at least one sugar-sweetened beverage a day had a 13 percent increased risk of hypertension, compared to those who only had a sweet drink once a month or less.
Similarly, people who drank at least one artificially-sweetened drink a day had a 14 percent increased risk of developing hypertension relative to those who had little or none.
The increases are fairly small, but, Cohen said, "over a large population, it is a significant risk."
According to the Centers for Disease Control and Prevention, about 30 of every 100 adults have hypertension.
A 13 percent increase in the population's risk would boost that number to about 34 in 100.
To see if it's the fructose in sugar-sweetened drinks that's responsible for the differences, the researchers also looked at people who had high levels of fructose in their diets from other sources, such as fruits.
"You would think if fructose were the causative factor, then eating a lot of apples (for example) would also increase your risk of hypertension," Cohen told Reuters Health.
Among the people who consumed 15 percent of their calories from fructose sources other than drinks, the risk of developing hypertension was either lower or the same as people who ate very little fructose.
"So our conclusion was that it couldn't be the fructose itself," Cohen said. "It has to be something else."
The findings take into account other diet and lifestyle factors that might influence hypertension risk, like overall diet quality, intake of alcohol, fats, fiber and certain vitamins, as well as smoking, physical activity level, contraceptive use and nonprescription painkiller use.
The researchers also adjusted for weight and weight changes over the study period as well as family history of hypertension.
Cohen's team looked for other factors that might explain the elevated risk for hypertension, such as caffeine, but nothing stuck out.
The "markedly" stronger link between carbonated sweet drinks and increased hypertension risk, versus noncarbonated drinks, might be explained by larger serving sizes associated with sodas, the researchers speculated, or some other unknown ingredient common to all of them.
Further research into the connections between sweet drinks and hypertension, as well as the underlying mechanisms is needed, Cohen told Reuters Health. Right now, "There really isn't a good explanation," she said.
SOURCE: bit.ly/JA2f76 Journal of General Internal Medicine, online April 27, 2012.