Drinking Milk as Teens May Not Protect Men's Bones
Instead, research found boys who consumed more milk had higher risk of hip fractures as adults
All participants were white, and milk-consumption histories (primarily involving whole milk) focused on the ages of 13 to 18. The participants' histories were provided solely on the basis of personal recall.
More than 35,000 men and nearly 62,000 women were tracked for 22 years. During this time, 490 hip fractures occurred among men and more than 1,200 occurred among women.
First, the researchers accounted for a number of possible influencing factors, such as current diet, weight, smoking history, exercise patterns, prescription drug use and current milk-consumption habits. They then determined that a man's risk for a hip fracture actually increased 9 percent for every additional daily glass of milk he had consumed while a teen.
However, no increase in adult hip fracture risk was seen among teen girls who drank more milk.
"The gender difference might be explained by several things," Feskanich said. "Difference in when women attain full height and maturity, or the fact that bone density is a bigger issue for men than women -- perhaps more of an issue than height. But at this point we're just hypothesizing."
Although the study found an association between more milk consumption in boyhood and higher risk of hip fractures in adulthood, it did not establish a cause-and-effect relationship.
In an editorial accompanying the study, Connie Weaver, a distinguished professor in the department of nutrition science at Purdue University, suggested that the findings may be flawed due to problems with the study's premise.
"When you look at the different findings concerning men and women, there are a number of reasons to ask if there is some problem with the study approach," she said.
"First of all, basic physiology among men and women ought to be the same, because calcium is the major mineral in all our bones," she said. "Their theory holds together based on the proposition that drinking milk will make boys taller and more prone to breaking bones, but the impact on height really shouldn't be different for boys and girls."
"There's also the fact that, both sexually and in terms of bones, boys and girls do develop at a different rate," she said. "To get an accurate look at the impact of teenage milk consumption, maybe the timelines shouldn't have been lined up to be exactly the same."