Despite everything we’ve been told about milk building strong bones and making us healthy, that may not be the case once we’re middle-aged adults, a new Swedish study suggests.
Researchers from Uppsala University followed more than 100,000 men (ages 45 to 79) and women (ages 39 to 74) for up to 20 years and found that those who drank three or more glasses of milk a day had a higher rate of death. Even more troubling, the women had more, not fewer, bone fractures.
The research, published Oct. 28 in the British Medical Journal, is one of several recent studies questioning whether increased consumption of milk in older adults really protects against bone loss and fractures. The U.S dietary guidelines, for example, call for adults to drink three cups of milk a day, but public health experts at Harvard note that it’s still not clear how much milk is optimal.
Lead author Karl Michaëlsson, a professor at Uppsala, said he had been studying fractures for 25 years and was puzzled because “there has again and again been a tendency of a higher risk of fracture with a higher intake of milk,” he told the Washington Post.
In the study, women who drank three or more glasses a day had twice the chance of dying at the end of the study as did those who drank less than one glass a day, he said. They also had a 50 percent higher risk of hip fracture. Men drinking that much milk had a higher risk of cardiovascular death.
One possible explanation, the researchers wrote, could be the high level of natural sugars consumed by drinking that much milk, which other animal studies have found can increase inflammation and cause changes in bone density.
On the other hand, eating cheese, yogurt and other fermented milk products — which have a low level of sugar — seemed to have an opposite effect, protecting women against both death and bone fractures, the scientists reported. For each serving of these kinds of dairy products, the rate of death and hip fractures was reduced by 10 to 15 percent in women.
The researchers cautioned that the study showed only an association between high milk consumption and fractures, not solid evidence of cause and effect.
In an editorial accompanying the study, C. Mary Schooling, a professor of public health at the City University of New York, urged more research into milk’s health effects as we age: “As milk features in many dietary guidelines and both hip fractures and cardiovascular disease are relatively common among older people, improving the evidence base for dietary recommendations could have substantial benefits for everyone.”
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