Bones are complex organs and rather than being static as most people think, are in constant dynamic change, adapting and adjusting to all the knocks and traumas and changes in lifestyle that we throw at them on a daily basis. They are constantly being remodelled with some areas being reabsorbed (by osteoclasts) and new bone being laid in other areas (by osteoblasts).
Bones are made from a protein (collagen) scaffold matrix, that give them their shape, structure and flexibility, but for their strength and resilience they need calcium, which is laid down on the scaffold in complex molecules with phosphate, carbonate, silicon and zinc.
Bones also contain 10 – 15% water and most importantly, in the long bones, bone marrow, which is essential for production of blood.
So keeping bones healthy is quite a complicated job!
Exercise and in particular, weight bearing exercise such as brisk walks, light jogging etc is essential for telling the regulatory processes in the bones to keep them in good and strong shape. Gravity is really important for this and one of the dilemmas facing long haul space flights and prolonged periods of time in the International Space Lab, is that bones rapidly melt away in the absence of gravity and weight bearing. So a good brisk walk once a day is not only good for your heart, but also good for your bones!
This doesn’t mean only eating salads, vegetables and fish! Fast food is fine once in a while, but a diet that is balanced and is protein and mineral rich, is good for bones. Milk and cheese are always hailed as being high in calcium but other foods such as green vegetables, citrus fruits, fish, nuts, tofu and beans also provide good amounts of calcium for those of us who don’t fancy dairy products or are lactose intolerant. Vitamin D (which is essential for calcium absorption) is also found in high amounts in these foods.
Calcium that we eat, still has to get from our gut and into our bloodstream in order for it to be used in bone maintenance. This is achieved by vitamin D, but the vitamin D that we take in has to be processed within the body in order for it to be activated. The first part of this activation process occurs in the kidneys, but the 2nd part occurs in the skin, but only if sunlight hits the skin. So in countries where there isn’t much sunlight (at the poles for example) or where traditional clothing hides the skin from sunlight, the condition rickets still occurs. This is where the scaffold structure of the bones has not been adequately mineralised by calcium and the bones are bendy and weak giving rise to ‘bandy legs’.
A similar condition is seen in areas of the world near volcanic activity where there are very high concentrations of fluoride in the drinking water and fluoride, which has a comparatively weak structure, gets preferentially incorporated into bones rather than calcium. In small amounts, fluoride helps to strengthen bone and enamel.
Amazingly, circulating sex hormones (testosterone in men, and oestrogens and progestogens in women), have a huge impact on bone development and remodelling. They also have an effect on joint flexibility and ligaments. That is why, in the latter stages of pregnancy, the pelvis is able to adapt and widen to allow the baby to begin its journey through the birth canal and into the bright blue world.
Normal circulating levels of these hormones are essential for the healthy collagen scaffold of bones. However, as levels of the female sex hormones start to drop off towards menopause, the collagen content of bones also starts to fall which may lead to osteoporosis and brittle bones in later life. The bones are brittle and snap easily because although containing plenty of calcium, the essential scaffold is weak. Replacing calcium is therefore not enough and there is a group of drugs called ‘bisphosponates’ which help to ‘shore up’ the scaffold and are often prescribed to women in later life.
This is one of the arguments in favour of HRT for post menopausal women.
Similar problems can also occur in men with low testosterone levels, either naturally, or deliberately as in the management of prostate cancer for example.
Sadly these do have an effect on calcium balance within the body. Alcohol, smoking, caffeine and even chocolate can have a deleterious effect on calcium and collagen metabolism and cause osteoporosis if consumed in high quantities!
Too much salt in the diet can reduce the amount of calcium that is absorbed. It binds with ingested calcium and is then excreted by the bowel
Oxalates are naturally occurring in certain types of food. They also bind with calcium and prevent its absorption in the gut. These foods include spinach, chard, certain berries, fizzy sodas and chocolate. So reducing your intake of these may have a beneficial effect on your bones.
MOTs are a good idea. They are a general check-up of health in middle age and are designed to prevent problems in the future and prolong life. There is no doubt that often unrecognised chronic conditions may lead to poor quality bones. These include, chronic kidney disease, chronic liver disease, poor quality diet and intestinal conditions such as coeliac disease, may all have an effect in causing osteoporosis and impaired calcium absorption. So if you get offered an MOT by your GP, grasp the nettle!
At the end of the day, a life spent taking regular exercise, eating well and not overindulging should give your bones the longevity they need to see you out!!
If you wish to discuss this or any other health issue please contact Dr Webberley