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Milk Products and Bone Health: Potential Mechanisms

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

Protein

• 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

Phosphorus

• 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.

Keywords: health studies , bone health