Calcium and bone strength
Our bodies use calcium for many reasons, including function of nerves and muscles and blood clotting. If we don’t have enough calcium for these needs our bodies will start drawing calcium from our bones. The result: weak, easily broken bones. So it is important we get enough calcium, by eating calcium-rich foods and possibly by taking calcium supplements (in conjunction with your doctor's recommendations).
Bone consists mainly of collagen protein fibres, with calcium and phosphate between these fibres to give strength and rigidity. The amount of collagen present, and therefore the amount of bone, depends on the balance between two types of cells - bone forming cells and bone resorbing cells. If our calcium supply is inadequate to meet all the body’s demands our bone resorbing cells will move into action, redistributing calcium from bones to other parts of the body.
Dairy products, including low-fat dairy foods that contain good levels of calcium include: milk, yoghurt, cheese, and ice cream. In a general adult population, calcium intake of around 1000-1500mg daily is considered desirable. That may require about four servings of calcium-rich foods every day. Many older people may feel uncomfortable trying to eat those quantities and instead prefer to take calcium supplements to top up their dietary intake (discuss dosage with your doctor). Calcium alone will not completely stop bone loss, but it can slow it down.
There is some controversy in the medical community about the use of calcium supplements, due to some studies showing an increased risk of heart problems in older adults taking these supplements. So it is recommended to discuss calcium supplementation with your doctor.
Vitamin D has important role
Calcium can only be fully absorbed if the body has enough vitamin D. Unlike other vitamins, vitamin D does not come mainly from food; it is made in the skin as a result of direct exposure to sunlight. Many older people lack vitamin D because they don’t spend enough time outside in the sun. For people at risk of low vitamin D levels, your doctor may prescribe a once-a-month vitamin D tablet. If you are concerned about vitamin D, talk to your doctor. Also see: Vitamin D and sun safety
Calcitriol is also a form of vitamin D that helps the body absorb calcium and incorporate it into bone. However, supervision by a doctor is needed as it can raise calcium too much.
Bisphosphonates are phosphate salts that bind to the bone surface and help prevent the activity of bone resorbing cells. Bisphosphonates help prevent further bone loss and reduce the risk of fractures, and can also increase bone density. Bisphosphonates are often a first-line treatment for osteoporosis.
Bisphosphonate medicines include:
- alendronate (oral tablet)
- etidronate (oral tablet)
- zoledronic acid (once-yearly intravenous infusion).
Bisphosphonates are extremely insoluble. When taken orally, the dosing instructions must be followed precisely to ensure the maximum amount is absorbed - and to reduce the possibility of side effects such as indigestion.
- Take the dose first thing in the morning with a full glass of water, at least half an hour before eating.
- Water only: the tablets should be taken only with water, as milk, tea, coffee or fruit juice interfere with their absorption.
- Remain upright (sitting or standing) for at least half an hour after taking the tablet. This prevents it sliding back into the oesophagus, where it may cause irritation and heartburn.
- Do not take calcium tablets at the same time of day.
Hormone replacement therapy (HRT/HT)
After menopause, all women experience a decline in bone density. This is directly linked to the lower levels of sex hormones produced by the ovaries. Hormone replacement therapy (HRT/HT) - the medical administration of ovarian sex hormones, or similar compounds - can restore a woman’s hormones to pre-menopausal levels. Oestrogen is the hormone that influences bone density, and hormone replacement therapy has been used in the past to help prevent osteoporosis.
More recent studies into the balance of risks and benefits with HRT means that HRT is no longer recommended as the first choice treatment for preventing osteoporosis in women. It is more commonly used for a restricted period to treat symptoms at the time of menopause. However, it may still be useful for osteoporosis in some circumstances. Men with low testosterone levels may also benefit from testosterone replacement.
Selective oestrogen receptor modulators (SERMs)
Selective oestrogen receptor modulators (SERMs) are another treatment for osteoporosis, and are useful in some people. In some tissues SERMs mimic the effects of oestrogen, while in other tissues it blocks the actions of oestrogen. This pattern of effects varies from one SERM to another. Raloxifene is the most commonly used SERM for osteoporosis.
Other types of treatment may be used to strengthen bones, depending on your individual health factors and whether you have other medical conditions. These include: tibolone metabolites; strontium ranelate; teriparatide; and denosumab.
For full information on prescription medicines for osteoporosis, go to www.medsafe.govt.nz (Consumer Medicines Information)
Original material by everybody. Updated April 2013.