Osteoporosis, or brittle bones, often has an underlying dietary basis, and good nutrition can help you maintain strong bones and reduce your risk of future fractures. Osteoporosis develops when the process of bone remodelling becomes unbalanced so that not enough new bone is made to replace the old, worn-out bone that is continually reabsorbed. As a result, your bones start to thin and become more brittle.
Osteoporosis is unfortunately a silent disease, with few symptoms or signs even when bone thinning is advanced. Sometimes the diagnosis is made when an X-ray is taken for other reasons, but often the first indication of the problem is a bone fracture (eg of a wrist or hip) after a minor fall. According to the International Osteoporosis Foundation, a fracture due to brittle bones occurs once every 3 seconds world-wide. An estimated 1 in 3 women over the age of 50 will be affected, as will 1 in 5 men.
What are the risk factors for osteoporosis?
The female hormone, oestrogen, strongly stimulates the formation of healthy, new bone so women are relatively protected against osteoporosis until they reach the menopause. The main female risk factors for osteoporosis are therefore linked with lack of oestrogen, and include:
- early menopause (before age 45)
- early hysterectomy (before the age of 45) especially if both ovaries are also removed
- loss of periods for any cause except pregnancy, such as excessive dieting and weight loss, excessive exercise or use of depot progestogen contraception.
Non-oestrogen-related risk factors that increase the risk of osteoporosis include:
- close family history – especially if your mother or father had a hip fracture
- long-term use of high-dose, corticosteroid tablets
- certain medical conditions such as adrenal, liver or thyroid problems
- being housebound with little exposure to sunlight to make vitamin D
- low dietary intakes of vitamin D, calcium magnesium and phosphorus
- intestinal malabsorption (eg due to coeliac disease, Crohn’s disease, gastric surgery)
- long-term immobility, especially confinement to bed in childhood
- heavy drinking
These non-oestrogen risk factors also apply to men, who are at additional risk if they also have low levels of the male hormone, testosterone (testosterone deficiency syndrome).
Although osteoporosis is often thought of as an older person’s disease, it affects an increasing number of younger women. So, if any of the above risk factors apply to you, it’s worth taking steps now to help safeguard your future bone health.
Despite its prevalence, osteoporosis is largely a preventable disease. Nutrition plays a massive role in reducing your risk and in treating brittle bones once the condition is diagnosed.
Calcium and osteoporosis
Calcium is an important structural mineral in your bones and good calcium intakes are vital at all stages of life. Calcium-rich foods include dairy products, green leafy vegetables (especially broccoli, but not spinach whose oxalate content reduces its bioavailability), tinned salmon/pilchards (because these contain small, calcium-rich bones), eggs, nuts, seeds, pulses plus white and brown bread made from fortified flour.
The easiest way to boost your intake is to drink an extra pint of milk per day which provides around 720mg calcium – skimmed or semi-skimmed milk provides slightly more than full-fat.
Interestingly, the bioavailability of calcium in brassica vegetables (cabbage and turnip family) is higher than that in dairy products. For example, 61% of the calcium found in broccoli is absorbable, compared with only 32% of that in milk. The reason remains unknown. Only 30–40 per cent of the calcium present in other food and drinks is absorbed.
Some types of dietary fibre (phytates from wheat in unleavened bread e.g. chapatti) also bind calcium in the bowel to form an insoluble, non-absorbable salt. High-fibre diets, which speed the passage of food through the bowels, will also reduce the amount of calcium absorbed.
Phosphorus and osteoporosis
Phosphorus is just as important for bones as calcium as it forms part of the bone structural salt, calcium phosphate (hydroxyapatite). Phosphorus is obtained from many food sources, including meats, eggs, dairy products, whole grains, pulses, nuts and yeast extract. As phosphorus is widely found in the diet, deficiency is rare but can develop in people using antacids containing aluminium hydroxide long-term which impairs absorption of phosphates from the gut.
Vitamin D and osteoporosis
Vitamin D is essential for the absorption of dietary calcium and phosphate in your small intestines and for their deposition in bones. Vitamin D also promotes the reabsorption of calcium in the kidneys, so less is lost in urine, reduces the secretion of parathyroid hormone from the parathyroid glands (to reduce the release of calcium from bones) and helps to maintain the balance between production and breakdown of bone. Just 15 minutes exposure to bright sunshine on your face makes enough vitamin D in your skin during spring and summer on days when the UV index is greater than 3. Throughout autumn and winter, at northern climes, your blood levels plummet and diet becomes even more important, as discussed here. Good dietary sources of vitamin D include oily fish, liver, eggs, butter, fortified milk and fortified margarine/spreads.
Magnesium and osteoporosis
Magnesium is a mineral needed for over 300 body enzymes to work properly. It is essential for every metabolic reaction in the body, including the activity of parathyroid hormone and the regulation of calcium deposition in bone. Women with osteoporosis tend to have lower magnesium levels than similar women without osteoporosis. Dietary sources of magnesium include beans (especially soy), nuts, wholegrains seafood, and dark green, leafy vegetables. Chocolate and drinking water in hard-water areas are also important sources for some people.
Vitamin K and osteoporosis
Three types of compound have vitamin K activity. Ninety percent of dietary intake is in the form of vitamin K1, and just 10% in the form of the more useful K2, which also has benefits on the heart and circulation. Probiotic bacteria in the gut also produce some vitamin K2 which you can absorb and use. Vitamin K is needed for the synthesis of osteocalcin – a calcium-binding protein found in bone matrix – and is as important for bone health as calcium.
Dietary sources include cauliflower, broccoli, and dark green leaves such as spinach, kale and some lettuces which provide more than 100mcg vitamin K1 per 100g. Useful amounts are also found in yoghurt (produced by the bacteria present), egg yolk, alfalfa, safflower, rapeseed, soya and olive oils, fish liver oils, liver, tomatoes, meat, potatoes and pulses.
Fruit And Veg and osteoporosis
Getting your 5-a-day is important as plant foods are an excellent source of bone-friendly substances such as isoflavones, vitamin C, vitamin K and carotenoids, as well as minerals such as potassium, magnesium, boron, copper, manganese, potassium, silica and zinc.
Oily Fish and ostoporosis
Fish such as salmon, mackerel, herring, sardines and fresh (not tinned) tuna are a rich source of omega-3 essential fatty acids which stimulate calcium uptake from the gut, decrease calcium loss in the urine and increase calcium deposition in your bones. They are also a good source of vitamin D, as is cod liver oil.
Where To Go Easy…
Cut back on salty foods as table salt (sodium chloride) increases the loss of calcium through your kidneys. Halving average salt intakes could cut urinary calcium losses by as much as 20%, as well as having beneficial effects on blood pressure.
Avoid canned, fizzy drinks which contain phosphoric acid as high intakes increase the loss of calcium from your bones.
Consider cutting back on caffeine if you drink lots of coffee. A large analysis of over 61,000 Swedish women suggested that, after taking other factors into account, a high coffee intake (≥4 cups daily) was associated with a 2%-4% lower bone density compared with women who drank little coffee (<1 cup daily). Although this was associated with a 28% increased risk of osteoporosis, however, this did not translate into an increased risk of fracture. To offset the effect of caffeine on bones, some experts suggest obtaining an extra 40g calcium for every 6 fl oz (178 ml) cup of caffeinated coffee consumed.
Avoid heavy consumption of red meat which may reduce absorption of dietary calcium and has been linked with low bone mass and early osteoporosis. This appears to be due to protein increasing the loss of calcium through the kidneys.
A US study involving almost 86,000 women aged 35-59 found that women who ate five or more servings of red meat per week were 23% more likely to experience a forearm fracture than women who ate red meat less than once per week, but there was no association between protein intake and hip fractures. They did not find any association between bone fractures and intake of vegetable protein. Best advice for red meat lovers it do have it no more than once a day and preferably only three or four times a week’ have more vegetarian and fish dishes, instead.
Avoid excess alcohol, which reduces the absorption of calcium from your diet and has a direct toxic effect on bone cells. The resulting adverse effects of heavy alcohol use on bone loss cannot be reversed, even if you cut back on drinking. Thankfully, moderate intakes of alcohol may actually increase bone density although the reason is not yet known, so keeping within recommended alcohol intakes is fine.
Lifestyle choices and osteoporosis
Regular exercise stimulates the formation of new bone. High impact exercise is best (eg aerobics, gymnastics, netball, dancing, racquet sports, jogging, skipping) but non-weight-bearing exercise such as stretching and swimming are also beneficial as they cause slight bone bending that triggers the strengthening process. You don’t have to over-do it, as significant benefits were shown from just jumping up and down 10 to 30 times per day. For older people, any form of activity is useful, including walking, climbing stairs, carrying loads, doing housework and gardening – these activities also strengthen muscles to reduce the likelihood of a fall.
Avoid smoking cigarettes as these lower levels of the female hormone, oestrogen enough to trigger an early menopause and premature osteoporosis. Smoking also lowers testosterone in men, which reduces bone formation as well as having adverse effects on erectile function. In fact, current smokers lose bone faster than non-smokers so that, by the age of 80 their bones have a 6% lower bone mineral density than if they had never smoked. A large analysis of data from 29 studies concluded that one in eight hip fractures is attributable to cigarette smoking.
Avoid excess stress which has been linked with an increased risk of osteoporosis as stress hormones have a direct harmful effect on bone. Cortisol, for example, increases calcium resorption from bone, increases calcium loss in the urine and also reduces production of sex hormones by the adrenal glands which provide useful top-ups in later life.
Avoid aluminium-based antacids which impair absorption of phosphates from the gut – regular use for more than 10 years may double the risk of a hip fracture.
Preventing osteoporosis with supplements
A multivitamin and mineral supplement or a formulation designed for bones is a good idea as a nutritional safety net, especially if you know your diet is not as good as it could be.
Calcium and Vitamin D Supplements
A daily calcium supplement can reduce and even prevent bone loss in older women, especially during the winter months when vitamin D levels are low. A large analysis of data from 29 trials, involving almost 64,000 adults, aged 50 or over, showed that calcium supplements could reduce the rate of bone loss and reduce the risk of all types of fracture by 12%. The study, published in The Lancet, found that where compliance was good, the protection against fractures was even greater at 24%. The most effective doses were 1200mg calcium plus 800 IU vitamin D.
Calcium tablets are best taken with meals. Some evidence suggests that they are better taken with an evening meal rather than breakfast as calcium flux is greatest in the body at night, when growth hormone is secreted.
As a bonus, a Canadian osteoporosis study involving over 9000 women found that women taking calcium supplements at a dose of up to 1000mg per day were 22% less likely to die over the 10 year follow-up period than women who did not take calcium supplements.
NB The upper safe level for long-term use of calcium supplements is suggested as 1500mg. People with a tendency to kidney stones should ideally take calcium supplements together with essential fatty acids (eg fish oils, evening primrose oil) but always seek medical advice first.
Vitamin D Supplements
Results from 12 studies, involving over 42,000 adults, found that taking vitamin D supplements alone reduced the risk of hip fractures by 9% and other non-vertebral fractures by 14%. Studies using higher doses of over 10 mcg (400 IU) vitamin D per day showed greater benefits, reducing bone fractures by at least 20%. The lead author later commented that everyone age 65 and older should take around 20mcg (800 IU) vitamin D3 per day for bone health benefits.
The European Food Safety Authority recently reviewed all the safety evidence and suggested the upper safe level is 100mcg per day (4000 IU). Excess can lead to side effects associated with high calcium levels, such as demineralisation of bone, kidney stones, headache and weakness.
Look for supplements supplying vitamin D3 (cholecalciferol) as this is more effective in maintaining blood vitamin D levels than the vitamin D2 (ergocalciferol) form.
A review of studies involving magnesium supplements concluded that taking at least 250mg magnesium supplements daily for two years could significantly increase bone mineral density, and prevent bone fractures. Despite these positive findings, twenty years ago, little recent research has been carried out since.
The EU recommended daily amount (RDA) is 375mg magnesium per day. The upper safe limit for long-term use from supplements is 400mg per day. Higher doses can have a laxative effect.
Vitamin K supplements
Lack of vitamin K increases the risk of osteoporosis, and taking high dose supplements for at least 6 months has been shown to reduce bone calcium loss in post-menopausal women by up to 50%, as well as strengthening bones that are already weakened. In 13 trials, all but one showed a significant protective effect of vitamin K supplements against bone loss. In seven trials vitamin K2 reduced the risk of vertebral fractures by 60%, hip fractures by 77% and all other non-vertebral fractures by 81%. NB Vitamin K2 is approved as a medical treatment for osteoporosis in Japan.
The EU RDA for vitamin K is 75 mcg. The upper safe level for long-term use from supplements is suggested as 1000 mcg (1mg). Higher doses used for treating osteoporosis should only be used under medical supervision.
Where possible look for supplements containing vitamin K2 rather than vitamin K1 to also obtain the circulatory benefits.
NB: Seek medical advice before taking supplements containing vitamin K if you are taking warfarin or have a blood clotting disorder.
If you are pregnant or breast-feeding, only take supplements designed for use at these times, as some supplements may be harmful.
Do not exceed recommended doses.
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