Written by: Jyoti Madhusoodanan, Ph.D. | Issue # 118 | 2024
- Analysis of data extracted from the Nurses Health Study that began in 1980 revealed that total dairy intake was linked to a lower risk of fractures in middle-aged and older women.
- Consuming milk, yogurt, and cheese was correlated with a lower risk of fragility fractures of the hip.
- The protective effects of dairy could benefit women both before and after menopause.
For many people, aging increases their risk of a fracture from a slip or fall from standing height or even more minor injuries. These injuries usually reveal the underlying condition of osteoporosis, characterized by low bone mineral density and a loss of the micro-architecture of bone tissue. Approximately 1.5 million new cases of fragility fractures are diagnosed annually in the U.S. alone . Although older women are considered most at risk of these injuries, a recent analysis revealed that the risk of fragility fractures begins to increase when women are in their forties .
Dairy consumption is thought to improve bone mineral density because foods such as milk and cheese are rich in calcium, phosphorus, and other minerals important for bone health. Despite this connection, the correlation between a dairy-rich diet and fracture risk has been tenuous. A 2018 study reported that an extra daily serving of dairy, at least half of which was milk, was linked to a 6 percent decrease in risk of hip fracture amongst postmenopausal women in the Nurses’ Health Study (NHS) . But some other studies have found no correlation between dairy consumption and hip fracture risk , while others have found that drinking milk can reduce these fractures.
In a new study, researchers led by Lynn Moore of the Boston University Chobanian & Avedisian School of Medicine set out to better understand whether dairy consumption could protect bone health in middle-aged and older women . The researchers turned to data from a large cohort of women included in the NHS, a study that tracked the health of female nurses starting in 1980. The researchers homed in on data for approximately 103,000 participants in the study. They excluded participants with a history of osteoporosis, previous fragility fractures, and those with missing information on dairy intake.
The team also examined participants’ exercise habits, medical history, and nutrition information collected in food frequency questionnaires that were sent to the study participants every few years. They included milk, cheese, and yogurt in their definition of dairy but left out butter, cream cheese, and cream because of the scant amounts of calcium present in these foods. Over the 24-year period of available data, there were a total of 5494 fractures across the participants.
In their analyses, funded in part by the National Dairy Council, the researchers discovered that women who consumed 2 or more daily servings of dairy—and milk in particular—had experienced fewer fractures than those who consumed the lowest amounts of dairy. Women who consumed more than 1 serving of cheese each day also had lower rates of fractures compared with those who ate less than 1 serving of cheese weekly. But the researchers found no correlation between eating yogurt and reduced fracture risk. Overall, dairy consumption appeared to benefit women who were postmenopausal as well as those who were under the age of 65.
The protective effects of dairy did not seem to be a result of the diet’s calcium content alone, because calcium from non-dairy sources was not correlated with a lower risk of fracture. The bone boost linked to dairy appeared independent of women’s consumption of calcium, vitamin D, or protein from non-dairy foods in their diet.
The inconclusive results of earlier studies may have stemmed from variations in the kinds of dairy consumed in different parts of the world, the authors suggest. For instance, their analysis of women in the U.S. found no link between yogurt and bone health, but yogurt consumption in this cohort  was much lower than their consumption of milk and cheese. Another reason for the variability amongst studies could be the quality of dairy. For example, a recent meta-analysis of studies conducted in 14 cohorts suggested that in the U.S., one extra serving of milk each day reduced the risk of hip fractures by 7 percent, but this correlation did not exist in studies of Scandinavian populations—perhaps because milk in the U.S. is often fortified with vitamin D .
Although the current study  is one of the largest of its kind, the authors noted that since nurses are likely to be more health-aware and practice healthy behaviors, there may have been other unmeasured preventive actions that contributed to the observed links between dairy and bone health. Future studies should aim to analyze whether high-fat and low-fat dairy products confer different protective effects, they suggested in their discussion of the results. Nonetheless, they concluded that the present data to a protective effect of milk and dairy products against fragility fractures in women. They concluded in their study that “this ﬁnding may provide middle-aged and older females with one of a series of methods for preventing future fractures.”
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