Food for Thought Archives...

Cheery, Beer-y Kidneys

Those who have suffered the excruciating pain of kidney stones usually ask themselves what they could have done differently. Pirjo Pietinen and her colleagues in Finland now think they have an answer: Drink beer.

As part of an ongoing lung-cancer prevention study, Pietinen’s group collected detailed dietary information from their 27,000 male volunteers. All were smokers between the ages of 50 and 69. Within about 6 years of entering the study, 329 of the participants developed kidney stones.

Ordinarily, physicians advise people at high risk of recurring stones to drink plenty of liquids, especially water. Diluting the urine seems to slow the buildup of the stony calcium deposits that cause pain.

However, all liquids are not equally beneficial. Studies have indicated that while coffee, tea, and alcohol tend to reduce an individual’s risk of forming kidney stones, grapefruit and apple juices both foster stone production. At least one study also indicated that soft-drink consumption might cultivate stones.

In these Finnish men, however, the researchers found no clear protection associated with water consumption. Then again, Pietinen notes, "our measure of total water was not as good as it should be, because the questionnaire we used didn’t ask about water drunk as such." Rather, they calculated water intake based upon its usual contribution to other foods—such as soup or tea.

Though asking questions directly about water consumption might seem an essential first step in any study of kidney stones, Pietinen points out that this was actually a re-crunching of numbers collected as part of a lung-cancer study. This also explains why her group restricted participation to individuals who smoked.

Unlike other studies, the Finnish scientists found no statistically significant link between alcohol consumption and kidney-stone risk. "What’s interesting in our data," Pietinen told Science News Online, "was that beer seemed to have a specific effect all its own."

For each bottle of the brew that a man downed daily, his risk of stone formation fell by 40 percent. "So, theoretically, drinking two beers a day could reduce your risk by 80 percent," Pietinen says. However, she’s quick to add, that’s a population average. "Certainly, we couldn’t say that if you drink 2.5 bottles of beer a day that you would never have kidney stones. There is no such guarantee."

She’s currently puzzling over why beer seems so beneficial. One hypothesis: The hops used to flavor beer may contain chemicals that interfere with stone formation.

A second study, this one conducted at the University of Wisconsin-Madison Medical School, found that although light-to-moderate drinking appears to reduce an individual’s risk of heart disease, those benefits seem greatest among persons with adult-onset diabetes (SN: 7/24/99, p. 52).

Among diabetics, those who regularly downed a drink a day—be it a mug of beer, glass of wine, or shot of whiskey—faced just 20 percent of the heart-disease-mortality risk seen in teetotalers. That’s significant because diabetics, in general, face an especially high risk of heart disease.

While this study couldn’t identify how alcohol protects, various studies in recent years have raised at least three possibilities, Valmadrid says. First, alcohol seems to have some general effect that retards the development of atherosclerosis—a buildup of fatty deposits in arteries. Other studies have suggested that at least some types of alcohol—especially dark beers (5/4/96, p. 287)—can dampen the susceptibility of blood to form clots. Finally, he notes, at least a few recent studies have suggested that alcohol consumption can actually improve the effectiveness of insulin. An insensitivity to insulin underlies diabetes.

Speculates Valmadrid, "There may even be a synergism between the three mechanisms, such that the effects are potentiated by the combination of all three."

Before you decide to toast these findings with a libation of your own, take heed of a common warning issued by both research teams. Their findings suggest a benefit in light-to-moderate alcohol consumption but should never be interpreted as a license to overindulge.

Prepared by Janet Raloff, senior editor of Science News.