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Moderate Drinking May Help, Not Harm, Kidneys, Study Finds

Men who had a drink or so a day fared better on renal performance tests than abstainers

Jacob Gaffney

Posted: Thursday, May 19, 2005

Conventional wisdom has held that alcohol was a sworn enemy of the kidneys, the twin organs responsible for filtering impurities in the blood and passing them from the body. However, this belief is being challenged by a new study that has found that a drink or two a day may lower the risk of kidney failure.

The study, published in the May 9 issue of the Archives of Internal Medicine, found that men who consumed at least seven drinks in a week showed a 29 percent lower risk of renal dysfunction than nondrinkers and infrequent drinkers. Men who had five to six drinks a week had an 8 percent lower risk. The study did not distinguish among different types of alcohol.

"This is the first study to show a consistent reduction in the risk of chronic kidney disease with light to moderate drinking," said study coauthor Tobias Kurth, a researcher at the Harvard University-affiliated Brigham and Women's Hospital, in a statement. He said the data in his study is not surprising, as moderate drinking is linked to a reduced risk of cardiovascular disease and traditional cardiovascular risk factors are associated with kidney disease, according to other recent research.

Kurth and his team looked at data from more than 11,000 volunteers in the long-term Physicians' Health Study, which ran from 1982 to 1995. That research, which originally sought to examine the link between taking aspirin and heart disease, focused on healthy male doctors, ages 45 to 70, who answered questionnaires on their lifestyles and reported the results of their physicals. Annual follow-ups were done, and blood samples were submitted at the beginning and the end of the study.

Kurth's team examined information from these blood samples for the purposes of their current study. They looked at the blood levels of a muscle-produced protein called creatinine and at the results of the men's glomerular filtration rate (GFR) tests.

Both tests help gauge how well the kidneys are filtering out waste products in the bloodstream. The GFR is measured by injecting low doses of a radioactive solution into the blood. After a few hours, a blood sample is taken and the amount of radiation still in the circulation system is calculated. If the kidneys are filtering properly, the radiation level should be comparatively low. Properly working kidneys will also remove comparatively high levels of creatinine.

The men were categorized by their level of alcohol consumption: no more than one drink a week (the majority being nondrinkers), two to four drinks per week, five to six drinks a week (defined by the authors as light consumption) and more than seven (defined by the authors as moderate consumption). While the research did not specifically define what constituted a drink, a typical serving would be 10 to 12 ounces of beer, 4 or 5 ounces of wine and 1 to 1.5 ounces of spirits.

The scientists then compared the men's test results to their level of alcohol consumption. They found that the men who drank seven or more drinks per week had the lowest levels of creatinine and the best GFR. This worked out to be a 29 percent reduced risk of kidney failure when compared to the lowest consumption category. While those who consumed five to six drinks a week saw some benefits, the men who had two to four drinks a week showed a similar risk for renal dysfunction as the nondrinkers and those who drank no more than once a week.

Not many physicians reported high levels of consumption so the effects of heavy drinking were not measured in this research. However, Kurth added, the harmful effects of heavy drinking on the kidneys have been well-documented in other studies.

The text added that at the heaviest levels of consumption, the men tended to be at higher risk for poor health in other areas; for example, they were more prone to hypertension and more likely to smoke. Because of these factors, the scientists warned against drinking for the singular purpose of trying to protect one's kidneys. "Conclusions about the overall effects of alcohol intake cannot be drawn from our study," they wrote.

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