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Synopsis: Bone Health and Osteoporosis

Milk product consumption is recognized as a key factor in bone health and in the prevention of osteoporosis. There is very good evidence that calcium and vitamin D, two essential components of milk, play important roles with respect to attaining peak bone mass and preventing osteoporosis and fractures. Emerging evidence also indicates that milk products are better than calcium and/or vitamin D supplements in maintaining bone health, indicating that other nutrients in milk products may serve an important function in this respect. These nutrients include:

• Protein,
• Potassium,
• Magnesium,
• Phosphorus,
• Vitamin B_12,
• Vitamin K,
• Zinc.

World-renowned bone health expert Robert P. Heaney summarizes the evidence related to how milk products affect bone health:¹

• Low fracture risk depends upon bone mass, bone architecture, and body mechanics (fall avoidance);
• Nutrients influence all three components listed above;
• Calcium, protein, and vitamin D are critically important for bone health, particularly considering that North American diets are deficient in these nutrients;
• Milk products are the most readily available sources for these nutrients, and diets low in milk products will almost always be low in one or more of the nutrients needed for healthy bones;
• It is difficult to devise a diet that is “bone healthy” without including 3 servings of milk products per day, not just because of dairy calcium but also because of dairy protein and potassium;
• Epidemiological studies report that a lifetime of high calcium intakes can reduce fracture risk by as much as 60%;
• Of 86 observational studies identified in an earlier review paper by Heaney in 2000, 64 reported relationships in favour of increased calcium intakes, with outcomes of reduced fracture risk, bone loss or improved bone mass;
• More than 100 additional studies have been published since Heaney’s 2000 review paper, with the majority of studies showing a positive effect (75 to 80% of studies) or no effect (20-25% of studies);
• Studies also indicate that milk and milk products provide a longer lasting skeletal benefit than that seen with calcium supplements;
• The available evidence supports the conclusion that optimal bone health requires adequate intakes of multiple nutrients, not just calcium;
• It is reasonable to conclude that the calcium sources that provide these other nutrients are at least as efficacious as the calcium supplements used in antifracture efficacy trials, and very likely more so;

The potential mechanisms by which milk products may have a beneficial impact on bone health and may prevent osteoporosis and fractures remain to be fully clarified, but several studies have identified mechanisms related to calcium and vitamin D, such as their role in offsetting obligatory losses, reducing excessive bone remodelling or turnover, and improving antifracture efficacy. Vitamin D may also have a role in neuromuscular function and fall prevention. Other nutrients found in milk products are also involved in important physiological functions related to bone health, such as bone mineralization and collagen formation. More studies on milk products and bone health across all age groups and on the efficacy of milk products in preventing osteoporosis and fractures are needed, as are studies looking at the role of specific milk products, especially yogurt and cheese. Mechanistic studies are also needed to clarify the role of other nutrients and components of milk products. For example, the role of protein, especially milk-based protein, needs to be clarified as does the role of other nutrients, such as potassium, vitamin K, vitamin B12, magnesium and zinc.

Keywords: bone health, osteoporosis

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