Bone health and osteoporosis

Milk and dairy products contain a number of nutrients that are required for building strong bones in childhood and for their maintenance during adulthood with the aim to reduce osteoporosis and bone fractures in older age (48). The European Commission has concluded that protein, calcium, phosphorus, magnesium, manganese, zinc, vitamin D, and vitamin K are necessary for maintaining normal bones (European Commission regulation 2012). With the exception of vitamin D, these nutrients are all present in significant amounts in milk and dairy products.

Osteoporosis has been described as a ‘paediatric disease with geriatric consequences’ as low milk, and hence, low mineral intake during childhood and adolescence has been associated with significantly increased risk of osteoporotic fractures in middle and older age, particularly in women (49, 50). A recent study indicated that in children and adolescents, except for those with very low calcium intakes, magnesium intake may be more important than calcium in relation to bone development (51). Calcium intake was found not to be significantly associated with total bone mineral content or density, whereas intake of magnesium and the amount absorbed were key predictors of bone mass. The extent to which these results can be extrapolated to the general population is uncertain, but milk and dairy products are important sources of magnesium and hence important supporters of bone growth during adolescence. In a meta-analysis by Huncharek et al. (52), dairy products, with or without vitamin D supplementation, increased total body and lumbar spine bone mineral content in children with low baseline dairy intake, whereas no effect was found for children with a high baseline dairy intake. Thus, there may be a threshold above which increasing intake of dairy products or dairy-calcium does not additionally benefit bone mineral content or density in children.

In adults, interactions between calcium, phosphorus, protein and vitamin D reduce bone resorption and increase bone formation, thereby attenuating age-related bone loss (53). Possibly due to the complex interaction between nutrients and the multifactorial nature of bone fractures, it has been difficult to establish whether or not a low intake of milk and dairy in adulthood increases the risk of osteoporosis and bone fractures. Hence, to date, meta-analyses have not supported a protective effect of milk and dairy intake in adulthood on risk of osteoporosis and bone fractures (54, 55). Nevertheless a recent systematic review concluded that calcium and dairy are important contributors to bone health in adults (56).

In the 2015–2020 Dietary Guidelines for Americans, it was stated that ‘Healthy eating patterns include fat-free and low-fat (1%) dairy, including milk, yoghurt, cheese, or fortified soy beverages (commonly known as “soymilk”). Those who are unable or choose not to consume dairy products should consume foods that provide the range of nutrients generally obtained from dairy, including protein, calcium, potassium, magnesium, vitamin D, and vitamin A (e.g. fortified soy beverages)’. Although the focus is on achieving the nutrient requirements by foods rather than supplements, plant-based beverages typically contain inorganic chemical forms of calcium, which may actually increase cardiovascular risk (56, 57). As calcium in dairy is organic, milk and dairy products should still be considered the superior sources of calcium (58). Yet, future studies need to address whether or not vitamin D fortification of dairy products is crucial for these to have a positive effect on bone fracture risk.

Conclusion on bone health and osteoporosis

The present evidence suggests a positive effect of milk and dairy intake on bone health in childhood and adolescence, but with only limited evidence on bone health in adulthood and on the risk of bone fractures in older age.

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