Moderate Drinking May Keep Women's Bones Stronger, Study Finds

Research on female twins in England found that those who drank moderately had denser bones than their twin sisters who drank rarely.

Identical twins may look alike on the outside, but their drinking habits may lead to differences on the inside, according to new research.

In a study of 46 pairs of female twins, scientists found that, if one twin drank moderately and the other drank rarely, the moderate drinker had "significantly denser bones both at the spine and the hip," said Tim Spector, a researcher in the Twin Research and Genetic Epidemiology Unit at St. Thomas' Hospital in London.

Denser bones help keep brittle bones at bay, Spector said. Healthy individuals are constantly breaking down and replacing bone, but brittle bones develop when the body reabsorbs necessary minerals from existing bones and doesn't form new bone. This condition may develop into osteoporosis, increasing the risk of bone fractures, especially in older individuals. Previous research has found that moderate wine drinking may increase bone mass in elderly women.

The study was initiated because "the effects of alcohol on bones were unclear," Spector said. And studying twins was particularly helpful, the authors wrote, because "[identical] twins are uniquely matched for age, sex and genetic factors, all of which are known to influence both bone mineral density and the propensity to consume alcohol."

The study first appeared online on July 1 in the Annals of the Rheumatic Diseases. For it, the scientists recruited pairs of adult female twins, of which one twin drank moderately (defined as up to three drinks a day in the United Kingdom) and the other twin had less than one drink per week. On average, the moderate drinkers consumed eight drinks per week. (The authors defined an average drink in England as a half-pint of beer, a 4- or 5-ounce glass of wine or a standard shot of spirits.)

The twins answered questionnaires on health and lifestyle details, such as smoking habits. To determine bone density, the women received X-rays of their hips and back. Blood and urine samples were also collected to examine the rate at which the body was reabsorbing bone.

The scientists then compared the twins' bone density and found that the moderate drinkers had "significantly" stronger bones than their twins who were nondrinkers or light drinkers. (Smokers had the thinnest bones in the group, the authors noted.) The moderate drinkers showed higher levels of minerals per square centimeter of bone, with an average density of 0.982 grams/cm2 in the hip, while the light drinkers had an average of 0.964 g/cm2. The moderate drinkers' spines had an average density of 1.020 g/cm2, and the light drinkers had 1.011 g/cm2.

However, the researchers also observed that the non- and light-drinking twins did not have lower-than-average bone density. That indicated that low levels of alcohol consumption do not increase the risk of brittle bones and that moderate consumption "may even be beneficial" to bone health, they wrote.

The scientists believe moderate alcohol consumption may exert a beneficial effect on bones through its effects on hormones or its "influence on the micro-architecture of the bone," rather than through a mechanism related to bone formation and reabsorption.

In the study, the researchers cautioned that twins may not reflective of the general population and that women who have more than 21 drinks a week are probably at a higher risk of fractures because of their "increased risk of falls."

But Spector said, if supported by further research, their results indicate that in the future "women with osteoporosis [may] be told [by physicians] that a glass of wine a day would be healthy" for their bones.

For a comprehensive look at the potential health benefits of drinking wine, check out senior editor Per-Henrik Mansson's feature Eat Well, Drink Wisely, Live Longer: The Science Behind A Healthy Life With Wine

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