BONE HEALTH
Osteoporosis is a disease in which bones become brittle, leading to an increased risk of fractures (broken bones). It is a silent disease that is largely treatable – and even preventable – in most people. However, without prevention or treatment, osteoporosis can progress causing pain, disability and loss of independence. The most common bones to break are the wrist, hip and spine, although any bone can be affected.
Osteoporosis can affect both men and women, and mostly after the age of52 years for women and 65 for men, although it is more common among women owing to lower levels of oestrogen during menopause. In South Africa the incidence of osteoporosis in white, Indian and mixed-race populations appears to be similar to that seen in developed countries, although no fracture data exist. Osteoporosis at the hip is less prevalent in black populations, although vertebral bone mass, and possibly also vertebral fracture prevalence, appears to be similar in black and white South Africans.
Dealing with osteoporosis is expensive. The direct annual cost of treating osteoporotic fractures in Canada, Europe and the USA is reported to amount up to US$6.5 trillion. This is without taking into account indirect costs such as disability and loss of productivity. Prevention of this disease can significantly reduce the costs incurred by the health system.
Bone health and strength are determined largely by factors outside our control, such as genetics, gender and age. However, factors that we can control, such as our diet and physical activity, can contribute to bone health and these are particularly important during adolescence, when bones are still developing. A balanced diet that provides ‘bone-friendly’ nutrients such as calcium, phosphorus, protein, vitamin D, zinc and magnesium is essential.
Dairy foods are rich in a number of these nutrients. (Although milk is not fortified with vitamin D in South Africa, regular exposure to 30–40 minutes of sunlight, before 11:00 or after 15:00, will give your body all the vitamin D it needs.)
Regular weight-bearing activity, in which you put the full weight of our body on our feet and legs, is also needed. Examples include jogging or brisk walking and playing sports. Further advice for a bone-friendly lifestyle includes maintaining a healthy weight, avoiding excessive alcohol intake and not smoking.
In addition to calcium, vitamin D and phosphate, adequate intake of dietary protein is recommended to keep bones healthy and prevent osteoporosis. This should already start in childhood and continue throughout life. Owing to the interaction between calcium and protein, both should be consumed in adequate amounts to optimise the beneficial dietary effects on bone health. Dairy products – especially milk – have optimal nutrient proportions for bone health, particularly with regard to the high calcium–protein ratio. Without dairy intake, it is difficult to meet calcium requirements and some of the beneficial effects of this mineral appear to be dairy specific. Individuals and nations should strive to increase the consumption of dairy as it has a health-economic impact: millions in health care costs related to hip fractures can be saved annually if dairy intake is increased.
There is a theory that the protein and phosphate in dairy products make them ‘acid producing’. Acid production could cause minerals to be leeched from the bones in order to neutralise the acid conditions, which would, in turn, compromise bone health.
However, the science does not support this theory. In fact, it is established that protein and phosphorus are essential nutrients for bone health. Milk and dairy products neither produce acid upon metabolism nor cause metabolic acidosis, and systemic pH is not influenced by the diet. In addition, the role of calcium in building and maintaining bones is well recognised and dairy foods such as milk, yoghurt and cheese are among the best dietary sources of this mineral.