Other foods and nutrients
There are other foods, and nutrients besides calcium and vitamin D, that contribute to bone health, including protein, fruits and vegetables, and other vitamins and minerals.
Protein
Adequate dietary protein is essential for optimal bone mass gain during childhood and adolescence, and preserving bone mass with ageing. Insufficient protein intake is common in the elderly and is more severe in hip fracture patients than in the general ageing population. Protein undernutrition also robs the muscles of mass and strength, heightening the risk of falls and fractures, and it contributes to poor recovery in patients who have had a fracture. Lean red meat, poultry and fish, as well as eggs and dairy foods are excellent sources of animal protein. Dairy foods offer the extra bonus of being a rich source of calcium, and oily fish, of vitamin D. Good vegetable sources of protein include legumes (e.g. lentils, kidney beans), soya products (e.g. tofu), grains, nuts and seeds.
Fruits and vegetables
Fruits and vegetables contain a whole array of vitamins, minerals, antioxidants, and alkaline salts, some or all of which can have a beneficial effect on bone. Studies have shown that higher fruit and vegetable consumption is associated with beneficial effects on bone density in elderly men and women, although the exact components which may give this benefit are still to be clarified.
Other vitamins and minerals
Vitamin K:
Vitamin K is required for the correct mineralization of bone. Some evidence suggests low vitamin K levels lead to low bone density and increased risk of fracture in the elderly, but more studies are needed to prove if increasing vitamin K intake would help to prevent or treat osteoporosis. Vitamin K sources include leafy green vegetables such as lettuce, spinach and cabbage, liver and some fermented cheeses and soyabean products.
Magnesium:
Magnesium plays an important role in forming bone mineral. Magnesium deficiency is rare in generally well-nourished populations. The elderly could potentially be at risk of mild magnesium deficiency, as magnesium absorption decreases and renal excretion increases with age, and also because certain medications promote magnesium loss in the urine. Particularly good sources of magnesium include green vegetables, legumes, nuts, seeds, unrefined grains, and fish.
Zinc:
This mineral is required for bone tissue renewal and mineralization. Severe deficiency is usually associated with calorie and protein malnutrition, and contributes to impaired bone growth in children. Milder degrees of zinc deficiency have been reported in the elderly and could potentially contribute to poor bone status. Lean red meat and meat products, poultry, whole grain cereals, pulses and legumes abundantly provide zinc.
B vitamins and homocysteine:
Some studies suggest that high blood levels of the amino acid homocysteine may be linked to lower bone density and higher risk of hip fracture in older persons. Vitamins B6 and B12, as well as folic acid, play a role in changing homocysteine into other amino acids for use by the body, so it is possible that they might play a protective role in osteoporosis. Further research is needed to test whether supplementation with these B vitamins might reduce fracture risk.
Vitamin A:
The role of vitamin A in osteoporosis risk is controversial. Vitamin A is present as a compound called retinol in foods of animal origin, such as liver and other offal, fish liver oils, dairy foods and egg yolk. Some plant foods contain a precursor of vitamin A, a group of compounds called carotenoids, for example in green leafy vegetables, and red and yellow colored fruits and vegetables. Consumption of vitamin A in amounts well above the recommended daily intake levels may have adverse effects on bone, the liver and skin. However, such high levels of vitamin A intake are probably only achieved through over-use of supplements, and intakes from food sources are not likely to pose a problem. Further research is needed into the role of vitamin A in bone health, although many countries at present caution against taking a fish liver oil supplement and a multivitamin supplement concurrently, as this could lead to excessive intake of vitamin A.
