Is Milk Bad for Your Bones?

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You’ve probably heard it your whole life: Milk builds healthy bones.

But could the age-old axiom actually be false? And could the opposite actually be true—could drinking lots of milk actually lead to more bone fractures and even increased mortality? According to a new study published in BMJ, milk may not be the all-star bone-builder we’ve  been led to believe, and it could actually be quite detrimental to our health when consumed in large quantities.

About the Study

Researchers in Sweden administered food frequency questionnaires to 61,433 women and 45,339 men, asking them to record their dietary habits and note how regularly they consumed certain foods, including dairy products like milk, cheese, and yogurt. The scientists then followed the women for 20 years and the men for 11, tracking how many participants developed bone fractures and how many actually died over the course of the study.

The results were somewhat startling: Higher milk intake was associated with higher incidences of bone fractures in women and higher mortality rates in both women and men. Women who drank at least three glasses of milk a day were almost twice as likely to die than women who drank less than one glass per day. It’s important to note, however, that the mean age of these women was 54 at the beginning of the study, and the age demographic of the participants may have played a part in the results. And although the findings seem to indicate that the occasional glass is probably unlikely to wreak major havoc, regular, heavy milk consumption could be linked with substantial health risks.

What the Researchers Discovered

The authors explicitly state that the results indicate only an association, not causation (in fact, a reverse causation could be possible, meaning the participants who had a higher risk for osteoporosis purposely drank more milk in an attempt to prevent bone loss).

They offer a possible explanation for the results: High doses of galactose, a sugar found in milk, have been found to induce premature aging and shortened life span in lab animals, although it’s unknown whether the same effect occurs in humans. One of the study’s authors, Karl Michaelsson, a professor at Uppsala University, told Live Science that galactose “might induce oxidative stress and low-grade inflammation, and that type of inflammation can affect mortality and fractures.”

Findings Don’t Apply to All Dairy Products

The study does offer some reassuring news for dairy lovers–fermented products like yogurt and cheese were actually associated with lower rates of fracture and mortality. Women who consumed fermented products were less likely to die or suffer fractures than those who did not. For each daily serving they consumed, the rates of mortality and hip fractures were reduced by 10 to 15 percent. One possible explanation: Fermented dairy products contain little or no galactose.  Interestingly, risk reductions in men who consumed fermented products were either not as pronounced or nonexistent.

Should You Pass on That Glass of Milk?

Not necessarily. According to One Medical Group nutritionist Karyn Duggan, CNC, there is no “one-size-fits-all” approach to nutrition, and dietary recommendations must be personalized.

Duggan does, however, encourage patients experiencing gastrointestinal problems to consider the possibility that dairy could be to blame. “If a patient is experiencing digestive issues I will often encourage him or her to explore an elimination diet–which includes elimination of dairy–for at least 21 to 28 days to see if symptoms improve, and often they do.”

Because of the study’s observational design, the authors state that the results should be interpreted with caution, and that further research is necessary before the findings can be used to influence dietary guidelines.

Duggan also reiterates that even the positive aspects of the study must be filtered through a personal lens. “It’s true that because yogurt is fermented, it’s more easily digested,” she says. “But again, it’s a very individual issue–it must be assessed on a case-by-case basis. Studies inform us and shape our opinions, but when it comes to making decisions, it’s always best to sit down with a trained professional who can offer guidance.”

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