The traditional medical paradigm for bone health is simplistic. Because bones contain calcium, eating more calcium must improve bone health. It is known that deficiencies of calcium cause bone deformities during development and can increase the risk of bone disease. However, bones are composed of more than just calcium. In particular, other minerals such as magnesium, phosphorus and boron are required for correct bone health. In addition, bones metabolism is under hormonal control, and this aspect is often overlooked. Studies that have investigated the role of supplemental calcium at improving bone health have shown inconsistent results, which supports the viewpoint that calcium is important, but is only one component of bone health. Nutritionists have long understood the role of a healthy diet in bone health, rather than the emphasis on single dietary components. More recently, the nutritional literature has confirmed that plant based diets show particular beneficial effects on bone health.
Osteoporosis is a common bone disorder characterised by a weakening of the bone caused by a chronic demineralisation. As minerals are removed from the bone, particularly calcium, the bone loses its strength and fracture rates increase significantly. Studies using calcium to treat osteoporosis have been inconsistent in their findings, and epidemiological studies show only weak associations between calcium intake of osteoporosis risk. The protective effect of plant based diets on the fracture risk in human populations shows an inverse association. For example, in one study1, researchers investigated the association between overall diet composition and fracture rates in Chinese subjects living in Singapore. The researchers collected diet data from a frequent food questionnaire and used a principal component analysis to identify patterns of food consumption within the diet in order to find particular protective components. The diet quality of the subjects was assessed using the Healthy Eating Index (2010).
The results of the study showed that two particular dietary patterns were inversely associated with fracture rates in the subjects. The vegetable-fruit-soy pattern and the Healthy Eating Index pattern both reduced the risk of developing hip fractures and in the case of the vegetable-fruit-soy pattern, these effects were dose related. Compared to the lowest intakes, those in the highest intake for vegetable-fruit-soy intake had a 34 % reduction is risk of fractures. Those subjects with the highest scores for the Health Eating Index had a 32 % reduction in fracture rates compared to those subjects with the lowest scores. In contrast, consuming the meat-dim-sum pattern of food, a traditional Cantonese eating pattern, was not associated with protection from osteoporosis. These results therefore support the contention that plant based diets are protective of fractures and support previous research showing beneficial effects for plant based diets against the formation of osteoporosis.
Plants are a good source of calcium and increasing plant foods is an effective way to increase calcium intake. Those eating plant based diets may therefore have higher intakes of calcium. However, plant based diets also tend to supply higher concentrations of other minerals, particularly magnesium. Therefore plant based diets may supply not only higher concentrations of minerals, but also supply more balanced intakes of a greater range of minerals. However, plant based diets may provide benefits in other ways. Meat based diets contain high amounts of sulphur containing amino acids and these may be metabolised to acid forming metabolites that lower the pH of the blood. As blood pH falls, minerals from bones are released to circulation to neutralise these metabolites and maintain correct blood pH. Plant based foods are metabolised to potassium salts that can raise the pH of the plasma, and this may therefore protect bone by decreasing this demineralising effect. The meat to plant ratio of the diet may therefore be required to be biased towards plant foods in order to protect bone health.
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