About this article
(a) Normal bone
Bone affected by osteoporosis
This article has been produced for anyone interested in finding out more about osteoporosis. You may have the con-dition yourself, or you may be a friend or relative of someone with osteo-porosis. Whatever reason you have for reading this, we hope you will find it useful. We want to explain as much as we can about osteoporosis – what causes it, how it can be prevented, and how it can be treated.
Unfortunately we cannot hope to answer all your questions, because every-one is different and this article is no substitute for individual consultation with a doctor.
What is osteoporosis?
The word ‘osteoporosis’ means, literally, ‘porous bone’. It is a condition where you gradually lose bone material so that your bones become more fragile. As a result, they are more likely to break even after a simple fall. Osteoporosis is common in South Africa.
How does it affect bones?
Bone is made of fibres of a material called collagen filled in with minerals – mainly calcium salts – rather like reinforced concrete. The bones of the skeleton have a thick outer shell or ‘cortex’, inside which there is ‘trabecular’ bone which is formed in a meshwork, as shown in Figure 1(a). Osteoporosis causes bone to be lost, leaving gaps in the bone material, as shown in Figure 1(b).
What causes osteoporosis?
Our bones grow during childhood and adolescence and are at their strongest in the late 20s. As middle age approaches the bones very gradually begin to become weaker. This weakening or thinning of the bones continues as we get older.
The process speeds up in women in the 10 years after the menopause. This is because the ovaries stop producing the female sex hormone oestrogen – and oestrogen is one of the substances that helps keep bones strong. Men suffer less from osteoporosis, because their bones are stronger in the first place and they do not go through the menopause.
Who is at risk?
All of us are at risk of developing osteoporosis as we get older, which is why elderly people are more likely to break bones when they fall. But there are some people who are more at risk of osteoporosis than others. These are some of the factors that can make a difference:
- Steroids: If you take prednisolone over a long period of time, it can lead to osteoporosis.
- Oestrogen deficiency: Women who have had an early menopause (before the age of 45), or a hysterectomy where one or both ovaries have been removed, are at greater risk. Removal of the ovaries only (ovariectomy) is relatively rare, but is also associated with an increased risk of osteoporosis.
- Lack of exercise: Moderate exercise keeps the bones strong during childhood and throughout adulthood. Anyone who does not exercise, or has an illness or disability which makes exercise difficult, will be more prone to losing calcium from the bones, and so more likely to develop osteoporosis. Exercise is, therefore, very important in preventing osteoporosis. (However, there is one case in which this is not true: for the small number of people who exercise very intensively, particularly women who exercise so much that their periods stop, the risk of osteoporosis may actually be increased.)
- Poor diet: A diet which does not include enough calcium or vitamin D can make osteoporosis more likely (see below).
- Heavy smoking: Tobacco lowers the oestrogen level in women and may cause early menopause. In men, smoking lowers testosterone activity and this can weaken the bones.
- Heavy drinking: A high alcohol intake reduces the ability of the body’s cells to make bone.
- Family history: Osteoporosis does run in families. This is probably because there are some inherited factors which affect the development of bone.
- Physical Build: Osteoporosis occurs more often among Caucasian and Asian women of lighter build than among larger women and most men of all races.
Can you prevent osteoporosis?
There is a great deal which can be done at different stages in your life to guard against the condition.
Healthy diet: Children and adults need a diet which contains the right amount of calcium. The best sources of this are milk, cheese and yogurt and, as shown below, certain types of fish which are eaten with the bones. If you are watching your weight it’s worth knowing that skimmed or semi-skimmed milk actually contains more calcium than full-fat milk. We recommend a daily intake of calcium of 1000 milligrams (mg) or 1500 mg if you are over 60.
A ½ litre of milk a day, together with a reasonable amount of other foods which contain calcium, should be sufficient (see Table 1). Vitamin D is needed for the body to absorb calcium. Vitamin D is produced by the body when sunlight falls on the skin, and it can be obtained from the diet (especially from oily fish) or vitamin supplements. For people over 60 it may be helpful to take a supplement containing 10–20 micrograms of vitamin D.
Table 1. Approximate calcium content of some common foods
60 g sardines or pilchards (including bones) 260 mg 0.2 litre semi-skimmed milk 230 mg 0.2 litre whole milk 220 mg 3 large slices brown or white bread 215 mg 125 g low-fat yogurt 205 mg 30 g hard cheese 190 mg 0.2 litre calcium-enriched soya milk 180 mg 125 g calcium-enriched soya yogurt 150 mg 115 g cottage cheese 145 mg 3 large slices wholewheat bread 125 mg 115 g baked beans 60 mg 115 g boiled cabbage 40 mg
- Children’s exercise: Children should actively take part in sports or other types of exercise to help strengthen their bones.
- Adult exercise: For the same reason, adults should keep physically active all the way into retirement. Choose ‘weight-bearing’ exercises (any activity which involves walking or running) which are of more benefit for bone strength than non-weight-bearing exercises such as swimming and cycling.
- Smoking: Avoid smoking. As previously mentioned, smoking can affect the hormones (in men and women) and may therefore increase the risk of osteoporosis.
- Drinking: Avoid drinking too much alcohol. The recom-mended daily maximum for a woman is 2–3 units. For a man it is 3–4 units. A unit is a single measure of 25 ml of spirits (40% alcohol by volume, or abv), or 0.3 litre of normal-strength beer, lager or cider (3.5% abv), or a very small glass (no more than 85 ml) of wine (12% abv).
How can osteoporosis be detected?
There are no obvious, physical signs of osteoporosis, because no one can see the bones getting ‘thinner’. Osteoporosis can go unnoticed for years without causing any symptoms. Quite often the first indication that someone has a problem is when s/he breaks a bone in what would normally have been a minor accident. Relatively minor fractures of the spinal bones can cause you to become round-shouldered and to lose height. These minor fractures may be painless but can cause back pain in some people. If a doctor suspects osteoporosis, s/he can order a scan to test the strength or density of the bones. This scan is now available at some hospitals throughout the country. The results will tell how much risk there is of the bones fracturing. You will need to lie on a couch, fully clothed, for about 15 minutes while your bones are x-rayed. The dose of x-rays is tiny – about the same as spending a day out in the sun. The technique is called dual energy x-ray absorptiometry (DEXA).
What are the consequences?
People with osteoporosis are more likely to break a bone even after a relatively minor accident. Fractures are most likely to the hip, spine or wrist. Hip and wrist fractures are usually sudden and the result of a fall. People who have previously had a fracture after a minor fall are at greater risk of further fractures.
Spinal problems occur if the bones in the spine (vertebrae) become weak and crush together. If several vertebrae are crushed, the spine will start to curve. This may cause back pain and loss of height and because there is then less space under the ribs, some people may have difficulty breathing. People who have this type of spinal problem also have an increased risk of fractures.
How can osteoporosis be treated?
Apart from the preventive measures already described there are other treatments available if you have osteoporosis. These may slow down the loss of bone or reduce the risk of fractures.
- Calcium and vitamin D: As mentioned earlier, people over 60 may benefit from taking small daily amounts of vitamin D, along with 1500 mg of calcium. Stronger vitamin D preparations are sometimes used to treat osteoporosis in younger people.
- Bisphosphonates: This group of drugs works by slowing bone loss; in many people, an increase in bone density can be measured over 5 years of treatment. Both alendronate and risedronate reduce the risk of hip and spine fractures in patients with osteoporosis. These drugs cannot be taken with food, and specific instructions on how to take the tablets are provided as they can cause irritation of the gullet. They are available either as daily-dose tablets or weekly-dose tablets.
- Hormone replacement therapy (HRT): Women who have been through the menopause may consider using hormone replacement therapy to reduce their menopausal symptoms. HRT is only beneficial for bones while it is being used. A very large clinical trial reported in 2002 that using the commonest type of HRT tablet is associated with a reduction in fracture, but also with a slight increase in the risk of heart disease and breast cancer. It can also increase the risk of venous thrombosis. If you are considering long-term HRT use, discuss the potential risks and benefits with your doctor.
- Selective estrogen receptor modulators (SERMs): As previously mentioned, the hormone oestrogen helps to keep the bones strong. Raloxifene is a SERM which mimics this effect and reduces spine fractures. It also reduces the risk of breast cancer without increasing the risk of heart disease. It is taken by mouth once a day without the need to follow special instructions. It may cause side-effects like menopausal ‘flushing’ and, as with HRT, may increase the risk of venous thrombosis.
- Calcitonin: Calcitonin is a substance which the body produces naturally and which helps keep the bones healthy. When used as a treatment it has enabled the bones of people with osteoporosis to grow stronger. Calcitonin can only be given in the form of an injection or by nasal spray. Injections of calcitonin are normally given only as a short-term treatment for painful vertebral fractures, but the nasal spray may be used as a long-term treatment for osteoporosis. Possible side-effects include hot flushes, nausea, an unpleasant taste in the mouth, tingling in the hands and, rarely, an allergic reaction. The nasal spray may also cause a blocked or runny nose, sneezing and headaches.
- Teriparatide: Teriparatide is a new drug which helps new bone to form and therefore reduces the risk of fractures. It is taken by daily injection into the thigh or tummy (patients are shown how to do this themselves). It is used for up to 18 months, during which time the bones are strengthened. At present it is used mainly for people who have had fractures despite using other treatments, or who have had side-effects from other treatments, or who have had nausea, limb pain, headaches and dizziness, but because it is a new drug any long-term side-effects are not known.
Leading an active healthy life and maintaining a diet with sufficient calcium is the best way of preventing osteoporosis. If you have the condition already, there are a number of treatments which can be effective, as described above.