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Bone Health: Studies in Adults and the Elderly

The Evidence

A 2015 meta-analysis of 15 randomized controlled trials (n = 1,533) by Tai et al. examined whether increasing calcium from dietary sources affects bone mineral density.¹

• Increasing calcium intake from dietary sources led to a small increase in bone mineral density (by 0.6%-1.8%) at all sites except the forearm;
• Similar results were obtained when the analyses were restricted to 12 randomized controlled trials of milk or dairy products.

A 2013 meta-analysis of randomized controlled trials investigated the effects of milk consumption on bone mass and bone turnover markers. The analysis consisted of 11 studies that included 2,397 adults. The authors concluded that dietary intervention with milk consumption has a favorable impact on bone metabolism and attenuates bone loss.²

• Compared to the control group, those who consumed milk had a significant increase in total body bone mineral density of 40.32 g (95% CI: 17.58-65.05);
• The intervention group also had a decrease in bone metabolism markers.

In a randomized double-blind controlled trial of 89 institutionalized elderly women, yogurt fortified with vitamin D or calcium was compared to non-fortified yogurt in terms of the capacity to lower serum parathyroid hormone and bone resorption markers:³

• Both the fortified and the non-fortified yogurt helped in the overall improvement of vitamin D status, parathyroid hormone and bone resorption markers;
• The favourable changes observed with the fortified yogurt were greater than those with the non-fortified yogurt.

Another randomized controlled trial, consisting of 40 postmenopausal women aged 55 to 65 years, found that calcium and vitamin D supplementation through fortified milk products had a beneficial impact on bone metabolism and bone mass indices. In addition, seasonal variations in hormonal and biochemical molecules appeared to be counterbalanced.⁴

A Japanese prospective cohort study of 1,479 adults aged 65 years or older concluded that greater milk intake was associated with lower bone turnover, higher bone density and higher bone microarchitecture. Specifically:⁵

• Greater milk consumption was associated with decreased bone turnover markers;
• Having ≥2 glasses of milk per day was associated with increased bone mineral density after adjustment for potential confounders such as height.

Data from the Framingham Offspring Study were examined to determine the association between milk product consumption and bone mineral density and hip fracture. The analytical sample included 2,733 participants with bone mineral density data and 3,212 adults with hip fracture data. The subjects were aged 26 to 85 years and followed for an average of 12 years.⁶

• A higher consumption of total dairy, milk and yogurt was associated with higher bone mineral density;
• Participants in the highest tertile of fluid dairy consumption (milk and yogurt) had a significantly lower risk of hip fracture than those in the lowest tertile, with a hazard ratio of 0.40 (95% CI: 0.17-0.99);
• The consumption of either milk or yogurt alone was associated with a lower but non-significant risk of hip fracture.

In a population-based cohort study of 625 women from Poland who were over 55 years old, the influence of calcium intake from milk products on hip bone mineral density and hip fracture incidence was investigated:⁷

• Those who had a higher intake of dairy calcium had an overall higher hip bone mineral density;
• The median dairy calcium intake was significantly lower in women who had previous fractures compared to those who did not (336 vs. 395 mg/day, p < 0.03).

Conclusion

The evidence indicates that dairy consumption is beneficial to bone health. Consumption of milk products, particularly milk, improves bone mineral density and appears to decrease bone loss.

There is limited evidence for milk products other than milk such as yogurt and cheese. More research is needed to better understand the role of total dairy intake and specific dairy products such as yogurt and cheese.

Keywords: bone health , calcium