How Does Milk Product Consumption Influence Fracture Risk?

Synopsis 

Although fracture risk is influenced by non-modifiable factors, such as age and sex, several lifestyle factors also play a role, namely diet, physical activity level and tobacco and alcohol use. Additionally, some chronic medical conditions and the long-term use of certain medications may increase fracture risk by weakening bones. Many variables, including genetic predisposition, may impact the effectiveness of interventions. 

Milk contains many essential nutrients and bioactive compounds that promote bone mineralization; and, it has traditionally been associated with strong bones. The overall evidence suggests that higher intakes of milk and milk products, including yogurt and cheese, are associated with a reduced risk of fractures in older adults. Dairy protein is associated with a reduced risk of fractures. Consuming milk products can help to promote peak bone mass development during the early years. Peak bone mass is a key predictor of reduced risk of osteoporosis and fractures later in life.

The evidence 

A 2019 meta-analysis by Matía-Martín et al. examined the association between intake of dairy products and the risk for osteoporotic fractures in non-Hispanic whites from North America and Europe.¹ Comparing the highest to the lowest level of dairy intake, this meta-analysis showed: 

• A higher total dairy intake was associated with an 18% reduced risk of vertebral fractures;
• A higher intake of yogurt and cheese was associated with an 8% and 11% reduced risk of fractures at any site; milk was not significantly associated with reduced risk. 

A 2018 meta-analysis by Bian et al. examined the association of dairy product consumption with hip fracture risk in 18 epidemiological studies (10 prospective cohort studies and 8 case-control studies).² This was the first meta-analysis to assess the role of yogurt and cheese, in addition to milk, on fracture risk. This meta-analysis found dairy foods were associated with lower hip fracture risk: 

• Yogurt and cheese were associated with a 25% and 32% reduced risk of hip fractures, respectively, in cohort studies.  
• Milk was associated with a 29% reduced risk of hip fractures in case-control studies. 

In 2018, Iguacel et al. published a meta-analysis that explored bone mineral density and facture risk in vegans, vegetarians and omnivores.³ This meta-analysis, which included data from 20 studies, with a total of 37,134 participants, found that:

• Compared to omnivores, vegans and vegetarians had a  lower bone mineral density, which was much lower in vegans than vegetarians; 
• Compared to omnivores, vegans also had an increased risk of fractures, which was not the case for vegetarians. 

In addition to recognizing the importance of calcium and vitamin D for bone health, the authors point to other key nutrients found in animal foods such as high-quality protein and vitamin B₁₂ as a potential explanation for these findings. 

In 2017, Feskanich et al. published a prospective cohort study that followed 123,906 older adults for up to 32 years.⁴ This study examined two large U.S. cohorts, including postmenopausal women from the Nurses’ Health Study and men over 50 years of age from the Health Professionals Follow-up Study. This study used multiple dietary assessments (at baseline and every 4 years) to assess long-term intake, thereby addressing an important issue of previous cohort studies that have mainly assessed intake at baseline only. This study found that: Higher long-term consumption of dairy foods was associated with a lower risk of hip fractures.

• Each daily serving of dairy foods, including milk, cheese and yogurt was associated with a 6% lower risk of hip fracture in men and women.  
• Those consuming higher milk intakes of 2 or more servings of milk per day had a 23% lower risk of hip fractures. 

Another prospective cohort study published by Langsetmo et al. in 2017 assessed protein intake by food source with fractures in older men⁵. Findings from this cohort, which included 5,875 men in the Osteoporosis Fractures in Men (MrOS) study, showed that:

• Dairy and non-dairy animal protein were associated with a reduced risk of hip fractures by 20% and 16% respectively, while plant protein was not associated with hip fracture risk; 
• Higher protein intake from animal sources (dairy and non-dairy) was associated with higher hip bone mineral density and lower hip fracture risk, while plant protein was not associated with these outcomes.  

 According to the 2016 U.S. National Osteoporosis Foundation’s Position Statement:⁶  

• There is strong evidence for calcium (Grade A) and good evidence (Grade B) for dairy products and vitamin D in peak bone mass development, a key predictor of fractures.    

Potential mechanisms 

The potential mechanisms underlying the association between milk product intake and fracture risk are not entirely understood, but they are likely related to the role of milk and milk products in bone mineral density, a key risk factor for osteoporosis and fractures. The 2016 U.S. National Osteoporosis Foundation’s Position Statement concluded that there is good evidence that milk products help to promote peak bone mass development in young adults. Achieving peak bone mass in younger years is critical for preventing osteoporosis and fractures later in life.⁶ Milk products provide a number of key nutrients that are important for bone health, including more calcium, protein, potassium, magnesium, zinc and phosphorus per calorie compared to any other food in the typical adult diet.⁷ 

Calcium and vitamin D 

According to the National Osteoporosis Foundation Position Statement, calcium and vitamin D are important for achieving peak bone mass in young adulthood. Peak bone mass is a key predictor of osteoporosis and fractures later in life.⁶  

Protein 

Current research indicates that protein is important for bone health. An adequate intake of protein is required for optimal bone growth and maintenance of healthy bone. In older adults, intakes above the current RDA (i.e., greater than 0.8 g/kg body weight/day) work in combination with adequate calcium intakes to help reduce bone loss and fracture risk, especially at the hip.⁸  

Other nutrients  

Calcium, protein, and vitamin D are described as being critically important for bone health.⁹ Potassium, magnesium, zinc, and several vitamins are also involved in bone health to varying extents.⁹ 

Conclusion 

The overall evidence indicates hat higher intakes of milk products, including milk, yogurt and cheese, are associated with a reduced risk of fractures in older adults.  

There is good evidence that the consumption of milk products helps to promote peak bone mass development. Milk products, calcium and vitamin D are important for achieving peak bone mass in young adulthood, which in turn is critical for preventing osteoporosis and fractures later in life. Milk products are also an important source of protein and other nutrients that contribute to bone health. 

The evidence also indicates that plant-based diets (especially those that exclude animal foods) may not support optimal bone health.