Bone Mineral Density & Osteoporosis
Bone mineral density (BMD) is mg mineral per cm2 bone.
In the old hypothesis, a high BMD is protective against osteoporosis, and therefore must be increased as much as possible.
But a low BMD due to a lifetime excessive calcium turnover is fundamentally different from a low BMD due to low calcium intake;
* BMD is highest and about similar in those countries where most milk is consumed and osteoporosis incidence is highest, like the USA, Australia, Switzerland, the UK and Northern Europe. (1) Italians also drink very much milk, have a high BMD, and Italian osteoporosis incidence is very high too. (2)
* BMD in Polish children is lower than US children (3), and so is milk consumption (22% less) and Polish osteoporosis incidence (4).
* Both BMD and hip fracture risk are lower in Chinese (5). And in some part of their bones they even have a higher BMD decrease rate (6). (but in some part of their bones the they reach peak BMD 5-10 years later than their counterparts, and is BMD decrease rate lower (7))
And their lower BMD is not due to genetic differences; Chinese who immigrated to Denmark more than 12 years ago have a similar BMD to that of the Danish. (8)
* Hip-BMD in Taiwanese is 10 to 15% lower as in Caucasians, and hip fracture incidence is, like in mainland Chinese, far lower. (9)
* Japanese osteoporosis incidence is also lower, and so is their BMD (10). And also BMD decrease rate is higher in some part of the bones. (11)
And this is not due to genetic differences either; America-born Japanese women have BMD values equivalent to those of whites. (12)
* Because fracture rates among African-American women are lower than among Caucasian women, ‘they’ thought African Americans therefore must have higher BMD, which however is not the case. (13)
* In Gambia, BMD, calcium intake and osteoporosis incidence is very low. (14) And again, this is not ‘genetic, since there are no significant differences in BMD and bone turnover in Gambian and Caucasian children living in the UK (15).
The belief of scientists that a high BMD is protective against osteoporosis, is based on a lower BMD in osteoporosis patients and in women.
But BMD in osteoporosis patients is lower due to excessive erosion. And in women BMD is lower due to a monthly increase in bone turnover, due to monthly fluctuations in estrogen level. (see ”Calcium Hormones”)
BMD on itself does not predict osteoporosis risk.
A natural low BMD due to a low calcium intake is protective against osteoporosis, for calcium turnover has been structurally low.
A low BMD caused by excessive calcium turnover is dangerous and enhances osteoporosis.
Many studies have shown that calcium intake (16) and physical activity can increase BMD. (17) Especially excessive high calcium intake (over 1200 mg) (18) and intensive physical training can. (19)
But because they body desperately tries to limit the intake of excessive calcium, also many studies have shown non-significant effects of calcium intake (or normal physical activity) on BMD. (20)
In elderly women BMD is either naturally decreased, which is not dangerous, or it is decreased due to excessive calcium turnover, which can cause osteoporosis.
If the low BMD is due to intake of too much calcium, physical exercise can increase BMD very effectively. And if BMD has naturally decreased, both excessive calcium and physical exercise can increase BMD values. That is why both physical activity and calcium intake can increase BMD values in elderly women very effectively. (21)
Abstracts of most sources can be found at The National Library of Medicin
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