As the human body ages, bones lose their density and become porous due to the progressive loss of minerals in the body.
Calcium is vital for making bones hard, but if the body eventually withdraws more calcium from the bones than has been deposited over the years, bones become weak, brittle and prone to fractures.
Postmenopausal women are especially vulnerable to osteoporosis because they no longer have the protection of the female hormones oestrogen and progesterone, which slow down bone loss. Hormone replacement therapy (HRT) can help to reduce the rate of bone loss, but since HRT can have its drawbacks, the risks need to be weighed carefully against the benefits. Heavy drinkers are also vulnerable, as the consumption of alcohol can hasten calcium loss. The risk of developing osteoporosis is also increased by smoking, which interferes with oestrogen production.
Until a person reaches his mid-30s, bone is being built but not lost, so bones reach their maximum density – known as peak bone mass – at some time in the mid-30s. From then on, bone starts to be lost. But as living bones are being rebuilt throughout life (an adult’s skeleton is replaced every seven years), it is never too late to take some positive action by improving the diet. Exercise is also necessary to build bone and prevent osteoporosis.
Medical experts agree that a healthy diet plays an important role in both preventing and treating osteoporosis. Calcium is the key to healthy bones, so the ideal way to prevent osteoporosis is to eat plenty of calcium-rich foods such as milk, cheese and yoghurt during childhood and adolescence. Low-fat varieties of these dairy products generally contain as much calcium as full-fat ones, so it is possible to obtain calcium without consuming too much saturated fat. Other good calcium sources include nuts (especially almonds), seeds, green leafy vegetables such as broccoli and watercress, tofu, and tinned sardines and pilchards when eaten with the bones.
For the body to absorb calcium efficiently, certain other nutrients need to be present; these include vitamin D and the minerals phosphorus and magnesium. Vitamin D is manufactured by the body through the action of sunlight on the skin, but it is also found in oily fish (herring, halibut, kippers, mackerel, pilchards, sardines, salmon, trout and tuna), eggs, and fortified margarine and breakfast cereals. Nuts, seeds and green leafy vegetables are rich sources of both calcium and magnesium, and phosphorus is found in many foods including fish, poultry, bread, cereals, rice and pasta.
Other minerals that play a role in the formation of bone include manganese, boron, zinc and copper. The best way to obtain these nutrients is to eat a varied diet of wholesome foods including nuts, seeds, green leafy vegetables, sea vegetables such as nori and kombu, fruit, whole grains, beans and shellfish.
An excess of fibre, salt or protein in the diet can interfere with the body’s ability to absorb calcium. Although protein is important for both bone formation and overall health, there is some evidence that protein from meats and dairy products may increase the loss of calcium from the body. For this reason, it is sensible to derive calcium from a wide variety of sources.