Milk Products and Bone Health: Potential Mechanisms
Milk products contain many nutrients, such as calcium, vitamin D, protein and phosphorus, which play a key role in the formation and maintenance of optimal bone health.
Calcium and phosphorus account for 80% to 90% of hydroxyapatite crystals, which make up bone mineral and play important roles for both bone rigidity and mobility. Protein, found in the bone matrix, also contributes to bone strength.1
A review of the potential mechanisms of nutrients found in milk products that play a role in bone health is presented below:
Calcium and vitamin D
- Offsetting obligatory losses
- Calcium and vitamin D are both needed to offset obligatory losses of calcium from the human skeleton. Vitamin D is necessary for efficient absorption of calcium from the diet, which in turn helps maintain blood calcium levels;1,2
- Calcium is recognized as a critical nutritional factor in achieving optimal peak bone mass.3
- Reducing excessive bone remodelling (turnover)
- Both calcium and vitamin D, particularly together, reduce excessive bone remodelling or turnover;2
- Both increased calcium intake and increased vitamin D status reduce bone remodelling because they reduce parathyroid hormone secretion.1,2
- Antifracture efficacy
- Calcium, as well as vitamin D which is needed for its absorption, helps maintain the structural strength of bones. Together, calcium and vitamin D contribute to increased bone mineral density, a key factor in reducing fracture risk.4
- Vitamin D and neuromuscular function
- Vitamin D has also been shown to improve lower-extremity neuromuscular function, increase muscle strength and reduce fall frequency.2,5
- Dietary protein plays many roles that may contribute to improving bone mineral density:1,6
- Increasing calcium absorption from the intestine;
- Decreasing bone resorption;
- Improving lean muscle mass and strength;
- Stimulating production of insulin-like growth factor 1 (IGF-1), a bone anabolic factor.
- The effect of increasing dietary protein on bone mineral density or bone mineral content is even more favourable when the level of both calcium and vitamin D is adequate.7
- Increasing phosphorus intake helps in the absorption and overall retention of calcium;7
- The calcium-phosphorus (Ca-Pi) ratio of dairy products appears to be optimal in supporting bone health during growth and adulthood. In particular, the Ca-Pi ratio in milk appears to favour a positive Ca-Pi balance that leads to bone matrix formation and mineral deposition.8
Interactions between calcium, vitamin D, phosphorus and protein
- Calcium, phosphorus, protein and vitamin D interact to reduce bone resorption and stimulate bone formation, which diminishes bone loss related to aging.7
In summary, milk products are one of the best available food sources that provide a combination of nutrients (calcium, vitamin D, protein and phosphorus) which contribute to bone health.
- Heaney RP. Dairy and bone health. J Am Coll Nutr 2009;28:82S-90S.
- Heaney RP. Bone health. Am J Clin Nutr 2007;85:300S-303S.
- Caroli A et al. Invited review: dairy intake and bone health: a viewpoint from the state of the art. J Dairy Sci 2011;94:5249-5262.
- Moore LL et al. Effects of average childhood dairy intake on adolescent bone health. J Pediatr 2008;153:667-673.
- Laird E et al. Vitamin D and bone health: potential mechanisms. Nutrients 2010;2:693-724.
- Mangano KM et al. Dietary protein is beneficial to bone health under conditions of adequate calcium intake: an update on clinical research. Curr Opin Clin Nutr Metab Care 2014;17:69-74.
- Bonjour JP et al. Dairy in adulthood: from foods to nutrient interactions on bone and skeletal muscle health. J Am Coll Nutr 2013;32:251-263.
- Bonjour JP. Calcium and phosphate: a duet of ions playing for bone health. J Am Coll Nutr 2011;30:438S-448S.