Think osteoporosis has nothing to do with you because you’re not old yet? Think again.
20 October 2011 is World Osteoporosis Day so I’ve been doing a bit of research.
I was horrified to discover that older women don’t break their hips when they fall, they fall because their hips have simply shattered in the course of normal everyday activities, due to osteoporosis – thin, brittle bones.
The trouble with osteoporosis is that we all think we don’t have to worry about it until we’re old. But it only occurs then if we don’t care for our bones properly throughout life. You may be aware that calcium is important for bone health, but there are a whole host of other nutrients you need as well to enable your body to build and maintain your bones.
It’s tempting to think that once we stop growing, our bones become inactive – fixed and rigid – but they’re actually very alive and changing all the time. The body is continually ‘borrowing’ calcium from the bones, and then returning it again, to balance acidity in the body, so our bone tissue is involved in a dynamic process of flux and change known as ‘remodelling’. This process is also essential to the repair of bones and joints, to keep them strong and flexible.
As we get older, the rebuilding process becomes less efficient, so that gradually more is taken from the bones than is returned. This happens particularly in women after the menopause, because oestrogen helps with the rebuilding process, and after menopause, oestrogen levels drop sharply. That’s why it’s so important to ensure you look after your bones when you’re younger – so that the gradual loss of strength which occurs after the menopause never reaches a critical point at which you’re vulnerable to fractures.
But there are many other factors apart from age which can affect bone health, and that’s why men are vulnerable to osteoporosis in later life as well as women, if they don’t ensure they maintain strong bones when they’re younger.
Nutritional and lifestyle factors are key for bone health: as well as plenty of load-bearing exercise to stimulate bone formation (running, brisk walking, weights work – including carrying shopping bags!), the right nutrition is crucial.
What to eat
Calcium – but is dairy really a good source?
Calcium is essential for bone health. Dairy products – milk, yoghurt, cheese – contain good amounts, but it has been suggested that dairy products increase the acidity in the body. This is because they contain protein which breaks down into amino acids, thus creating a state where the balance is tipped in favour of the bones releasing calcium rather than taking more on board. But there’s no clear evidence to support this 15, 16 , and as long as you’re eating plenty of fruit and vegetables, which metabolise to alkalilne substances in the body and balance acidity, you probably don’t need to worry about the acidifying effects of protein 12,13,14. In fact, it’s important to make sure you get enough protein – more of which later.
Other important nutrients found in dairy
These include Vitamin D is which is essential to enable the body to absorb and use calcium; Vitamin A, to enable the body to absorb and use both calcium and protein. It also plays a role in regulating the hormonal system, helping to ensure sufficient oestrogen production, which enables calcium to be laid down in the bones; finally vitamin K which is involved in the synthesis of the bone protein osteocalcin, required for bone mineralization. Vitamin K can be manufactured by good bacteria in the gut, supplied by ‘live’, or probiotic yoghurts.
The importance of protein
Protein is needed to make the matrix-like structure which holds the calcium and other minerals in the bone, and the softer cartilage which keeps your joints moving. Two or three palm-sized portions a day of lean meat, poultry, fish, or slightly bigger portions of vegetarian proteins such as beans or lentils, nuts and seeds alongside grains, should do it.
The importance of getting your 5-a-day
Many vegetables and other plant-based foods are a good source of, and in addition they provide other nutrients essential for bone health.
Leafy greens like cabbage, kale and broccoli (particularly purple sprouting broccoli) are sources of calcium.
They also provide magnesium which aids calcium absorption and is needed for the formation of the bone mineral, hydroxyapetite.
Leafy greens are also a good source of folic acid which is required to recycle a substance called homocysteine and stop it building up in the blood. Recent observational studies suggest that high homocysteine levels in the blood may be linked to lower bone mineral density and a higher risk of hip fracture in older people 17,18.
Onions, tomatoes and lettuce are good sources of chromium, which helps to reduce the excretion of calcium in the urine19.
Nuts, seeds, beans/legumes and grains are also good sources of calcium and magnesium: wholemeal bread, brown rice, wholemeal pasta, quinoa) and seeds like pumpkin seeds and sunflower seeds. Ideally wholegrain bread should be sour-dough, and beans/legumes should be well soaked, to reduce levels of phytic acid, which binds to calcium and inhibits absorption9.
Another important mineral is zinc is also found in foods like nuts and seeds. It is a constituent of the bone mineral, hydroxyapatite and helps to regulate bone turn-over. It’s also needed to enable an enzyme called alkaline phosphatase to work properly, which is involved in laying down minerals in bone to make it hard and strong.
Nuts, seeds and wholegrains also provide vitamin E, which is an antioxidant. Animal studies suggest it protects the mechanism by which calcium is deposited in the bones from damage by free-radicals 4,5. (Free radicals are damaging chemicals produced by the body’s own metabolic processes, that need to be balanced by anti-oxidants.)
Beans and pulses, especially soy, also contain phytoestrogens – weak plant oestrogens – which mimic the effects of natural oestrogens in the body. It is thought that they may help to prevent bone loss in women after the menopause, but though there has been some promising research in animals, the evidence isn’t conclusive22, 23.
Fruits, especially apples and dried fruits, alongside nuts and grains are also good sources of boron: prunes are a great source, dark leafy greens (in particular cabbage), apples, beans and peas. Boron is another key nutrient, needed for the conversion of vitamin D into its active form, which in turn enables calcium absorption. Boron has been shown to reduce the excretion of calcium and magnesium11 (more of which later).
Seafood and lean meat – prawns, oysters, chicken, lean beef – are other good sources of zinc. Animal proteins – meat, chicken, fish – also contain vitamin B12, which seems to have a role in maintaining bone density, possibly by inhibiting the activity of osteoblasts – the cells which break down bone10.
Dairy and animal proteins also contain phosphorus, which provides phosphate needed alongside calcium for bone formation.
Oily fish like salmon, sardines and mackerel are good sources of omega-3 good fats. It is thought these may help prevent bone loss as their anti-inflammatory properties blunt the effects of pro-inflammatory substances called cytokines which are produced by the immune system, and seem to be raised in the first few years after menopause 24.
What to avoid
It’s all the usual suspects which are implicated in poor bone health, but there’s one nice surprise too – and if you want to skip straight to the good news, scroll down – I’ve saved that for the end.
Refined carbohydrates and sugar
Avoiding refined carbohydrates like sugar, white bread and white rice may also help to maintain bone health, because these foods deplete chromium levels.
Too much salt
Salt contains sodium which encourages the loss of calcium in the urine. Although a high salt intake hasn’t been conclusively linked to a greater risk of osteoporosis, it makes logical sense, and there are other reasons, such as increased risk of stroke, to avoid excessive salt intake. The best advice is to stick to a maximum of 6g/day, which is about a teaspoonful. Ensure you read the ingredients on packets to check for hidden salt.
Coffee and colas
These contain caffeine, and your caffeine intake is something else to keep an eye on: it interferes with the natural balance of calcium and phosphorus, and increases the amount of calcium excreted in the urine.
Fizzy drinks like colas have also been implicated in bone-thinning and osteoporosis because of their high concentrations of phosphoric acid. This encourages the release of calcium from the bones to counteract the acidity, making bones thinner and weaker 20.
A high alcohol intake is believed to contribute to osteoporosis, especially in men 21.
Smoking is very bad news for bone health: it lowers oestrogen levels in the blood and inhibits the effects of oestrogen8.
Don’t be too slim (woo hoo!)
Because oestrogen, which helps the bones to lay down calcium, is made by fat tissue as well as the ovaries, it becomes a crucial source of oestrogen after menopause, so may not be a good idea to be very slim after the menopause. It is possible that one reason women naturally gain a little weight after the menopause is linked to protective effects on bone health: the extra fat supplies oestrogen that protects against bone loss. Very thin women are at greater risk of osteoporosis6,7.
- A Wachman and D S Bernstein, “Diet and osteoporosis” Lancet 1968 1:958
- Frey R Ellis, et al, “Incidence of osteoporosis in vegetarians and omnivores” American Journal of Clinical Nutrition, June 1972, 25:555-558
- Richard B Mazess and Warren Mather, “Bone mineral content of North Alaskan Eskimos” American Journal of Clinical Nutrition, September 1974 2:916-925
- Arimandi B et al (2002) Vitamin E improves bone quality in the aged but not in young adult male mice. J Nutr Biochem. 2002 Sep;13(9):543.
- BA Watkins et al, “Importance of Vitamin E in Bone Formation and in Chondrocyte Function” American Oil Chemists Society Proceedings, 1996, at Purdue University
- M E Nelson, “Hormone and bone mineral status in endurance-trained and sedentary postmenopausal women” Journal of Clinical Endocrinology and Metabolism May 1988, 66(5):927-933
- R N Baumgartner et al, “Associations of fat and muscle masses with bone mineral in elderly men and women”, American Journal of Clinical Nutrition 1996 63:365
- National Institute of Health Consensus Conference: “Osteoporosis” Journal of the American Medical Association August 1984 252(6):799-802
- Lindsey H Allen, “Calcium absorption and requirements during the life span”, Nutrition News, February 1984 47(1):1-3
10. USDA/Agricultural Research Service (2005, April 23). Fight Osteoporosis: Bone Up On B12.
11. Beattie, JH and Peace, HS. The influence of a low-boron diet and boron supplementation on bone, major mineral and sex steroid metabolism in postmenopausal women. Br J Nutr 1993 May;69(3):871-84
12. New SA. Nutritional Factors Influencing the Development and Maintenance of Bone Health Throughout the Life Cycle, World Congress on Osteoporosis 2000. Day 1 – June 15, 2000
13. New SA, Bolton-Smith C, Grubb DA, Reid DM. Nutritional influences on bone mineral density: a cross-sectional study in premenopausal women. Am J, Clin Nutr. 1997;65:1831-1839.
14. New SA, Smith R, Foulds E, Reid DM. Associations between present dietary intake and bone health in elderly Scottish men and women. In: Ring EFJ, Elvins DM, Bhalla AK, eds. Current Research in Osteoporosis and Bone Mineral Measurement V. London: British Institute of Radiology; 1998:3.
15. Sally Fallon and Mary G Enig (2000) Dem Bones: Do High Protein Diets Cause Bone Loss? http://www.westonaprice.org/osteoporosis/dem-bones
16. Jeannette M Beasley, Laura E Ichikawa, Brett A Ange, Leslie Spangler, Andrea Z LaCroix, Susan M Ott and Delia Scholes (2010) Is protein intake associated with bone mineral density in young women? American Journal of Clinical Nutrition, doi:10.
17. McLean RR, Jacques PF, Selhub J, et al. (2004) Homocysteine as a predictive factor for hip fracture in older persons. N Engl J Med 350:2042-49.
18. Morris MS, Jacques PF, Selhub J (2005) Relation between homocysteine and B-vitamin status indicators and bone mineral density in older Americans. Bone 37:234-42.
19. McCarthy, Med Hypotheses 1995 45:241-246
20. E Mazariegos-Ramos et al, “Consumption of soft drinks with phosphoric acid as a risk factor for the development of hypocalcemia in children: A case control study”, Journal of Pediatrics 1995 126:940-942
21. Herta Spencer, et al, “Chronic Alcoholism: Frequently Overlooked Cause of Osteoporosis in Men”, The American Journal of Medicine, March 1986 80:393-397
22. Spence LA, Lipscombe ER, Cadogan J, et al. (2005) The effect of soy protein and soy isoflavones on calcium metabolism in postmenopausal women; a randomized crossover study. Am J Clin Nutr 81:916-22.
23. Osteoporosis Prevention, Diagnosis, and Therapy. NIH Consensus Statement. Online 2000 March 27-29; [cited year, month, day]; 17(1): 1-36
24. Kettler, DB. Can Manipulation of the Ratios of Essential Fatty Acids Slow the Rapid Rate of Postmenopausal Bone Loss? Alternative Medicine Review – Volume 6, Number 1, February 2001