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Eating and living for strong, healthy bones

Tanya Haffner
BSc(Hons) RD RNutr
Dietitian
Nutritionist
Health Writer
London

Many nurses working in primary care will encounter people with osteoporosis. Women are more at risk because they do not attain as high a peak bone mineral density as men, and they suffer a period of accelerated bone loss in the first five years following menopause.(1) Approximately three- million people in the UK are affected by osteoporosis, and it is estimated to cost the NHS £1.7bn a year.(2) Cost alone does not take into account the distressing symptoms and the anxiety and reduced quality of life caused by having fragile bones, such as depression and the related social and personal implications.(3)
Our bones are alive and constantly changing. Old, worn-out bone cells are broken down and replaced by bone-building cells called osteoblasts. In childhood osteoblasts work faster, enabling the skeleton to increase in density and strength. After the age of 35, bone loss increases as part of the natural ageing process. This bone loss is more rapid in women following the menopause for several years, leading to an increased risk of broken bones. 
Although genetic make-up undoubtedly plays a role, lifestyle factors such as nutrition, physical activity and smoking can all contribute to bone strength.
It is important to strengthen bones in the first 30 years of life to accumulate calcium and other minerals that will help offset the effect of ageing, so targeting this age group is a top priority. However, research shows that a bone-friendly diet and lifestyle are useful at any age to strengthen bone and to help minimise bone loss.(4)

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How to help protect bones?
Incorporate daily weight-bearing exercise into your lifestyle
Weight-bearing exercise puts pressure on the bones, helping to strengthen them. It is important to try incorporating such exercise daily. This can be achieved by walking, running or standing, or just shifting weight from one foot to another while standing.

Enjoy a healthy balanced diet
Bones are complex and need nutrients such as vitamins, fatty acids, protein and minerals for optimum health. Although calcium is the most abundant mineral found in the skeleton, other nutrients play a crucial role. These can be found across the different food groups, including fruit and vegetables; bread, potatoes, pasta and cereals; milk and dairy products; and meat, fish eggs, pulses, nuts and seeds. A healthy balanced diet is not only good for bones; it also helps to reduce the risk of many other chronic diseases.

Ensure you gain enough calcium from your diet
Dietary calcium builds strong bones. Ideally, adults need between 700 and 1,000 mg/day of calcium. Rich sources of calcium include milk and dairy products and their calcium-enriched alternatives, but other food types can provide useful amounts of calcium. There is calcium in green leafy vegetables, for example, but because it is not as well absorbed you need to eat a lot more of these foods to get the equivalent of a regular glass of milk. The calcium in tofu and soya is well absorbed, and oily fish that contain bones are also a good source of calcium. Water can contain variable amounts of calcium depending on the source, and there are calcium-supplemented fruit juices available on the market now. Table 1 can be used to help your patients roughly assess how much calcium they might be getting from their diet. If your patient finds it hard to get this amount from their diet, you can encourage them to take a daily calcium supplement containing 400-600 mg of calcium, and
preferably one that contains vitamin D to help boost calcium absorption. Too much calcium in the diet may be detrimental since it can affect the absorption of other important minerals such as iron.

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Get adequate vitamin D from food, supplements or sunlight
Vitamin D is an essential partner to calcium. It releases calcium from the digestive tract into the bloodstream, making it available for absorption into the bones. The main source of vitamin D is by the action of sunlight on exposed skin. Those at risk of vitamin D deficiency include those who cover up outside, avoid the sun, are housebound or have darker-coloured skin. Statistics from the Department of Health have indicated that poor vitamin D status in the younger population is a major problem, strongly related to covering up our skin.(5,6) Wearing sunscreen higher than factor 8 reduces vitamin D production by 95%. Vitamin D from sunlight can be stored in the body for use throughout the year. It is recommended to expose skin for five to 15 minutes each day between 10am and 3pm during the summer months to make enough vitamin D for the year. However, too much sun exposure can increase the risk of skin cancer, so it is important to sunbathe carefully. A suntan does not indicate that one has enough vitamin D. If a patient is concerned about sun exposure then they should be informed that vitamin D can also be acquired by taking supplements.
For those patients who are housebound the current UK dietary recommendations are equivalent to one portion of oily fish or two eggs.
From the age of one, the recommended daily intake of vitamin D to help prevent osteoporosis is 10 mcg (400  IU). Those over 70 years or those who have been diagnosed with osteoporosis may be recommended to take 15 mcg a day (600  IU). Pregnant and breastfeeding women and young children should also take a vitamin D supplement, as should those with darker skin.

Consume adequate vitamin K
Consuming adequate vitamin K, found in green leafy vegetables, helps to form bone-hardening protein.

Make sure you have enough protein-containing foods in your diet
Healthy bone needs protein, so one should aim to eat two portions of meat, fish, dairy or alternatives such as tofu or pulses a day. However, diets high in protein should be avoided as they increase calcium loss from the body.(3)

Enjoy five portions of fruit and vegetables a day
Recent studies have shown a positive effect on bone health for those who have a high intake of fruit and vegetables. It was suggested that osteoporosis may be caused by long-term exposure to an acid-generating diet high in dietary protein.(7) Fruit and vegetables are protective because they balance the acidity generated in the body by eating too much protein. Alternatively, fruit and vegetables may be beneficial to bone because they contain nutrients that are involved in bone metabolism such as vitamin C (required for crosslinking collagen, which is the major structural protein of bone), vitamin K (needed to modifiy osteocalcin - a protein associated with osteoblasts), folate (known to reduce homocysteine, which has been shown to be a risk factor for fractures in the elderly),(8) phytoestrogens (which may act as weak agonists and antagonists of oestrogen) and flavonoids. Too little protein may also be detrimental. Data from the Women's Health Initiative study recently showed that women with extremes of potassium to protein intake (ie, too low or too high dietary protein intake) had increased risk of fracture compared with those in the middle range of intakes.

Watch your salt intake
A high salt intake can increase calcium loss from the body. It is now recommended that adults should not exceed 6 g of salt a day (equivalent to one teaspoon), and that we should preferably aim for less. Salt is so widespread in our diet that we don't need to add it during food preparation or at the table. If a patient has a high salt intake it is usually more successful to reduce it gradually. Many are surprised at how their palate quickly gets used to having less.

What about phytoestrogens?
Phytoestrogens - plant chemicals most commonly found in soya foods - have been shown in humans to act like the human oestrogen (although they are much weaker) and so may help protect against bone loss by mimicking oestrogen. However, while trials are promising, much more research is needed before any specific recommendations can be made.
With regard to consuming soya in general, it can be a good source of calcium, and calcium-enriched varieties of the dairy options such as soya milk and soya yogurts should be chosen.
Soya safety in relation to phytoestrogens has recently been an issue blown up in the press, but as part of a healthy balanced diet soya is completely safe and is more likely to have a number of long-term health benefits when consumed as such.

Other important lifestyle factors
Alcohol
Abuse of alcohol carries a significant risk for osteoporosis. Advice should be given not to exceed the governments recommended limits, which says that men should not drink more than three to four units of alcohol a day and women no more than two to three units per day (one unit of alcohol is equivalent to one small glass of wine, a measure of spirits or half a pint of normal-strength beer or cider). It is also good to have alcohol-free days. Interestingly, a moderate intake of one to two glasses of wine a day may have beneficial affects on the skeleton as well as the heart.

Dieting
A low body weight is a risk factor for breaking a bone, as is a high body weight. If you have overweight or obese patients it is important to reassure them that low-fat dairy products are just as good a source of calcium as their full-fat equivalents. It may be helpful to refer them to a registered dietitian.

Smoking
Smoking is well known to have detrimental effects on health. It has also been shown to slow down the work of our bone-building cells, the osteoblasts. Smoking may also result in an earlier menopause in some women.

Conclusion
While diet, exercise and lifestyle may not cure osteo­porosis, following these top lifestyle tips is important for helping to prevent bone loss and for keeping bones healthy.

References

  1. Macdonald HM, New SA, Campbell MK, Reid DM. Influence of weight and weight change on bone loss in perimenopausal and early postmenopausal Scottish women. Osteoporos Int 2005;16:163-71.
  2. Torgerson DJ, Iglesias CP, Reid DM. The economics of fracture prevention. In: Barlow DH, Frances RM, Miles A, editors. The effective managment of osteoporosis. London: Aesculapius Medical Press; 2001.
  3. Department of Health. Dietary reference values for food energy and nutrients for the United Kingdom. London: HMSO; 1991.
  4. Department of Health. Nutrition and bone health: with particular reference to calcium and vitamin D. London: HMSO; 1998.
  5. Tylavsky FA, Cheng S, Lyytikainen A, et al. Strategies to improve vitamin D status in northern European children: exploring the merits of vitamin D fortification and supplementation. J Nutr 2006;136:1130-4.
  6. Cashman KD. Vitamin D in childhood and adolescence.Postgrad Med J 2007;83:230-5.
  7. Cunningham W, Hyson D. The skinny on high-protein, low-carbohydrate diets. Prev Cardiol 2006;9:166-73.
  8. McLean RR, Jacques PF, Selhub J, et al. Homocysteine as a predictive factor for hip fracture in older persons. N Engl J Med 2004;350:2042-9.

Resources
Food Standards Agency
W: www.eatwell.gov.uk

British Dietetic Association
W: www.bda.org.uk

Smoking cessation
Quitline
W: www.quit.org.uk
T: 080 002200