Do you need a reason to cut down on sweetened beverages? Their fructose content might increase your blood pressure, doctors said Thursday.
Although not all studies agree, the findings add to a growing body of evidence that too much of the ubiquitous sugar – found in fruits as well as high-fructose corn syrup and table sugar – can have important health consequences. (See Reuters Health story of May 24, 2010.)
High blood pressure, for example, increases the risk of strokes, heart disease and kidney failure.
Close to one in three Americans suffer from elevated blood pressure, a rate that has tripled in the past century, the researchers say in the Journal of the American Society of Nephrology. While the reasons aren’t clear, diet and lifestyle changes are the main suspects.
To test the link between blood pressure and fructose, they used nationally representative survey data from more than 4,500 adults. The survey included questions about all sources of fructose, whereas most earlier studies had focused on soft drinks.
On average, they found, people said they consumed 74 grams of fructose per day – roughly the amount in four soft drinks. Even though none of them had experienced blood pressure problems, about a third turned out to have borderline high blood pressure and eight percent had hypertension (readings of at least 140/90 mmHg, compared with normal values of 120/80 or less).
The more fructose their diet included, the more likely they were to have high blood pressure. Of course, that could have been influenced by a variety of factors, such as obesity and disease, or getting too much of other sugars, salt or alcohol.
But even when adjusting for all these factors, the odds of having high blood pressure increased in those whose fructose intake was above average. For the most severe form – stage 2 hypertension – the odds were 77 percent higher.
Given the new findings, people might want to think twice about what they throw into their shopping carts, said Dr. Michel Chonchol of the University of Colorado Denver, who worked on the study.
“In the grocery store, you see food without high-fructose corn syrup,” he said, adding that it would make sense to reduce fructose intake by choosing those products and avoiding the ones containing added sugars.
“There is no question that fructose itself appears to have effects that other sugars don’t have,” said Chonchol. The exact mechanisms are unclear, although several have been proposed, he added.
“What we need now are clinical trials, where you take people with hypertension and place them on a diet with low fructose and see if that lowers their blood pressure,” said Rachel K. Johnson, a professor of nutrition at the University of Vermont in Burlington, who was not involved in the research.
Until then, she said the message is clear: “Sugar-sweetened beverages – avoid, avoid, avoid! That’s the major source of added sugars for Americans.”
Getting fructose from eating fruits appears to be less of a problem, she said, perhaps because they also contain many healthful substances like antioxidants and fiber. Fruit has just 4 to 10 grams of fructose per serving, while a can of Coca-Cola has 39 grams of high-fructose corn syrup, about half of which is fructose (the rest is glucose).
Last year, Johnson helped prepare a statement about sugar and heart disease from the American Heart Association, which included dietary recommendations.
“For most American women,” she advises, “no more than six teaspoons or 100 calories a day of added sugars, and no more than nine teaspoons for men.”
That is less than one can of Coca-Cola.
In a press release about the new study, the Corn Refiners Association, a U.S. trade group, said the researchers had muddled the differences between fructose and glucose, the other half of high-fructose corn syrup and table sugar.
“The rise in glucose consumption also mirrors the dramatic rise in hypertension,” the release said.