By Janet Raloff, Science News
Women don't develop gout—an arthritic condition prone to excruciatingly painful flare-ups—at nearly the same rate as men. But as in men, its incidence has been creeping up in women, according to a new report. Also as in men, a second new report finds, fructose-sweetened beverages appear to pose a particularly potent gout risk for women.
Potentially aggravating this trend: New data indicate that sweetened soft drinks appear to be a richer source of fructose than had been assumed.
The new data signal a dietary trend that can trigger pain and can potentially cripple joints—but is avoidable, says Martin Underwood of the University of Warwick Medical School in Coventry, England, who is unaffiliated with the new studies. Moreover, he adds, gout's growing incidence potentially points to an even bigger threat because studies have begun to point to gout as an independent risk factor for cardiovascular disease.
Gout develops when the blood becomes saturated with uric acid, a breakdown product of purines, which are a constituent of many foods, especially red and organ meats. When uric acid precipitates out into the joints and crystallizes, intense pain develops. Researchers consider severely elevated uric acid levels in blood, or hyperuricemia, a silent indicator of gout.
At the American College of Rheumatology meeting in Atlanta, Hyon Choi of the Boston University School of Medicine and his colleagues reported November 9 that incidence of hyperuricemia increases with age and now afflicts some 31 percent of U.S. adults 65 and older—an estimated 8.4 million people. Their data came from the most recent National Health and Nutrition Examination Survey, which interviewed and took health measurements from more than 24,000 adults selected to offer a representative cross section of Americans.
Women seldom develop gout pain prior to menopause, because female sex hormones help keep uric acid levels low, notes Choi. But after menopause, women's risk of the disease rises to about half of the rate in older U.S. men, he reports.
Over the past decade, Choi's team has uncovered a host of gout triggers. Two years ago, for instance, he and Gary Curhan of Harvard Medical School linked risk of the disease in men with elevated consumption of fructose—a principal sugar in fruit that is present in all sugar-sweetened beverages. It made sense, the researchers pointed out, since fructose independently triggers the body's production of uric acid from adenosine triphosphate, a molecule that stores and transports energy.
At a November 10 presentation at the rheumatology meeting, Choi, Curhan and Walter Willett of the Harvard School of Public Health now extend fructose's gout risk to women. Based on data collected from roughly 79,000 postmenopausal participants of the long-running Nurse's Health Study, the team shows that downing one sugar-sweetened soft drink per day increased a woman's risk of gout compared to women drinking less than one serving a month. Upping the consumption of sugary soft drinks to two or more servings a day appeared to have an even bigger effect.
The team's findings also appear online in the Journal of the American Medical Association.
In the United States, soft drink manufacturers almost invariably sweeten their nondiet offerings with high-fructose corn syrup. Unlike sucrose, or table sugar, which is a 50:50 combination of fructose and glucose, high-fructose corn syrup contains these sugars in a mix dominated by fructose.
Although the corn syrup industry has argued that the amount of extra fructose is small, with 55 percent fructose and 45 percent glucose, a new paper in Obesity challenges that. Michael Goran's team at the University of Southern California's Keck School of Medicine, in Los Angeles, locally collected samples of 23 different sugar-sweetened beverages. The researchers purchased most as canned or bottled drinks, but also collected six samples of soda-fountain beverages.
"All of the soft drinks," the team reports, "with the exception of the Mexican Coca-Cola, are 58 percent fructose or above, and the three most popular soft drinks [Coke, Pepsi and Sprite] contained 64 to 65 percent fructose."
And that's disturbing, Goran says, because unlike glucose, fructose is primarily broken down in the liver, where it can become a feedstock for new fat synthesis. Indeed, the nutritional physiologist notes, fructose is suspected of contributing to a serious and widespread condition known as fatty-liver disease.
The bottom line, Underwood says, is that reducing fructose in the diet—especially its exaggerated use in soft drinks—could do a lot to limit a sweetened beverage's health risks.
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