Bone Mineral Density & Bone Health
Bone health tends not to be of much interest to most of us until we or a relative breaks a bone in later life. 20% of elderly people who suffer a hip fracture aged 65+ die within the year, an example of the devastating effect breaking a bone can have on the elderly. You don’t have to be that old either: I’ve had a couple of clients who have suffered fractures in their 50’s and been diagnosed with osteopenia, the precursor to osteoporosis and the problem seems to be getting worse.
Bone health is a worldwide issue, affecting some populations more than others. In the past few decades, the global incidence of osteoporosis has increased dramatically with rising life expectancy, and over 200 million people suffer from osteoporosis worldwide. By 2050, the global cost of osteoporosis is expected to exceed $130 billion and the annual hip fracture incidence is expected to increase to 6.3 million. The highest risk of hip fractures is currently found in Norway, Sweden, Iceland, Denmark and the United States, but by 2050 Asia is expected to account for almost 50% of all global fractures.
Low BMD (bone mineral density) has been the cited as a factor in the incidence of osteoporosis, with advice such as taking calcium supplements and getting adequate amounts of exposure to sunlight (vitamin D is required for the body to absorb calcium) being the treatment, but I came across some interesting statistics (various sources available at The National Library of Medicin) and the bone health story is confusing: –
- BMD (bone mineral density) is highest in those countries where the most milk is consumed (milk being a good source of calcium) and osteoporosis incidence is also highest: USA, Australia, Switzerland, the UK and Northern Europe. Italians, for example, drink lots of milk, have a high BMD, but osteoporosis is also very high.
- Conversely, BMD in Polish children is lower than in American children, yet they drink over 20% less milk and the incidence of osteoporosis is also lower.
- BMD and hip fractures are both low in china.
- BMD in the hips is 10% to 15% lower for Taiwanese than in Caucasians, but hip fractures are also far lower.
- In Gambia, BMD, calcium intake and osteoporosis incidence are very low.
- A lot of milk is consumed in Kuwait and therefore their BMD is close to that of people in West-European countries, but so is osteoporosis in Kuwait.
- In the above countries where BMD, osteoporosis and fractures are low, genetics don’t play a part: it seems that immigrants have similar levels of all three as those people in their adopted country.
So it appears from the above that the hypothesis that a high BMD will ensure bone health and protect you against osteoporosis may not be entirely accurate. BMD by itself is not a good predictor of the risk of osteoporosis. From the information above, low BMD due to low calcium intake doesn’t appear to increase the risk of osteoporosis either, perhaps because calcium turnover has been low too. The problem occurs when the body loses more bone than it can produce, when the production of new bone cannot match the destruction. This breakdown of old bone and production of new bone is a natural process which takes place throughout our lives, but as we get older it slows down and is lost more quickly than it can be replaced. So why do some people suffer more than others with an imbalance in this process and go on to develop osteoporosis?
More next time, plus how yoga can help with bone health