If You've Been Told Drinking a Lot of Milk Is Good for Your Bones, You'll Want to See What This Study Found

There's a popular commercial for milk that says it "does the body good," but new research suggests that a lot of the calcium-rich product could actually have the opposite effect.

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While parents frequently tell their children they need to drink their milk to grow strong bones and the U.S. Department of Agriculture recommends most people get about three cups of dairy products each day, a large Swedish study found that drinking more cow's milk increased mortality and bone fracture rates in some adults.

The study published in the British Medical Journal looked at food questionnaires and a follow-up of more than 61,000 women 39 to 74 years old and more than 45,000 men 45 to 79 years old.

An average of 20 years after the initial questionnaire taken by women, more than 15,000 had died and more than 17,000 experienced some sort of fracture. In men an average of 11 years after the survey, more than 10,000 had died and more than 5,000 had a fracture.

When the factor of drinking three or more glass of milk per day was taken into account, the researchers saw mortality and fracture risk increase. New Scientist noted that only 10 percent of participants drank three glasses or more a day.

"High milk intake was associated with higher mortality in one cohort of women and in another cohort of men, and with higher fracture incidence in women," the study authors wrote.

More specifically, women who drank this much milk were almost twice as likely to die during the study period, compared to those drinking only one glass. The higher incidence of bone fractures among these avid milk drinkers compared to those who drank less was 16 percent.

"They're provocative findings, I know, but these are the facts," Karl Michaelsson with Uppsala University, which led the study, told New Scientist.  "The amount is important, so if you drink only small amounts, there's no problem."

The study also found fermented milk, like yogurt or cheese, did not have the same effect, but resulted in lower fracture and mortality rates.

The study authors urge some caution in interpreting these results and offer ideas for further research.

"Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures," they wrote. "The results should, however, be interpreted cautiously given the observational design of our study. The findings merit independent replication before they can be used for dietary recommendations."

If the study is replicated with similar results, Michaelsson told New Scientist he thinks the cause could be inflammation that results from the breakdown of lactose.

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