Drinking milk and risk of hip fractures

It's a tenet of nutrition, handed down from our parents and grandparents, and backed up by clever marketing campaigns. The specific message might vary, but the underlying belief is: "Drink milk for strong bones."

Milk contains a number of vitamins and minerals, not to mention protein and fat, and the presumption behind much of the research into bone health and milk has been, essentially, that:
1. Milk contains higher levels of calcium and vitamin D, and
2. Calcium and vitamin D are beneficial to bone health, therefore
3. Milk is beneficial to bone health

For decades this belief wasn't closely questioned - to the point that the USDA's MyPlate actually includes dairy milk as a beverage in its dietary recommendations.

More recent research, however, has looked at dairy intake (and more specifically at dairy intake in the form of liquid cow's milk) and any link there might be between a) consuming cows' milk itself or b) consuming supplements of calcium and Vitamin D and bone fracture. The results, however, have been mixed.

Back in 2014 we reported on a study that suggested that for women, higher intake of cheese and fermented dairy - not liquid milk - reduced their risk of fracture, while those who drank more than three glasses of milk per day increased their risk of fracture.

Worse yet, it would appear that taking calcium or vitamin D supplements in order to reduce the risk of fracture might actually increase your risk of heart attack or stroke.

With all of this conflicting data regarding milk, the components of milk thought to be bone-protective, and whether those protective components should be taken as supplements by themselves, for an Internist like me, who sees patients nearly every day, the really relevant question is the one our patients who are concerned about their bones often ask me: "Should I drink milk?"

Today's article was published in the British Journal of Nutrition (doi:10:1017/S0007114518003823) and is authored by a team of Norwegian researchers who analyzed data gathered through two large-scale, long term studies carried out in Norway.

The first source of data is known as the Norwegian Counties Study (with over 35,000 participants included in the analysis) and includes those participants from a larger cardiovascular health screening that recruited participants between 1985-86 and 1987-88. The second source of data comes from the Five Counties study (about 23,300 people included in the analysis), which includes 5 Norwegian counties of varying economic and locational areas, which began collecting data between 2000 and 2003 and continues to today.

Both data sources included at minimum the height, weight, and smoking data for all participants, and among other food groups queried the participants regarding their usual intake of milk, measured in "glasses of milk per day."

After an average of more than ten years' followup, the authors could access the country's hospital data to ascertain which participants might have experienced a hip fracture. They then compared the milk intake of those who fractured their hip with those who did not, taking into account such variables as Body Mass Index, age, gender, smoking status, chronic diseases, and other variables.

The authors found, and this is a direct quote from their discussion, "no clear association [either for or against] between milk consumption and risk of hip fracture."

What this means for you

These are results from people who are largely Caucasian, and the results could and probably are complicated by race, class, or more diverse gender. What this does suggest is that if you're drinking milk solely - or even mostly - for your bone health, you might reconsider. First, those glasses of milk may be calories you don't need, while the bone-related content of the milk (calcium, vitamin D) is likely available through other foods that offer you multiple other benefits, such as fiber or antioxidants (spinach is a good source of vitamin D, for example, and collards, broccoli rabe, and kale are higher in calcium foods).

First posted: February 20, 2018