B is for bones (B vitamins that is) part II
June 1, 2011
In last week's article I wrote about the importance of certain B vitamins in reducing elevated homocysteine levels. Homocysteine is an amino acid that is a by-product of protein metabolism. According to the homocysteine theory, elevated levels of this amino acid can cause osteoporosis.
Certain B vitamins can lower homocysteine levels. These are folic acid, vitamin B6, and vitamin B12. Last week;s article discussed folic acid and its relationship to osteoporosis. This week's article will discuss vitamin B6 and vitamin B12.
Like folic acid, B6 also plays a role in homocysteine metabolism. Studies have been done showing a relationship between vitamin B6 deficiency and osteoporosis. One such study done in 1972 and published in the journal Biochemical Medicine showed that rats receiving a B6 deficient diet developed osteoporosis.
A 1992 study on human subjects published in Clinical Science found a relationship between pernicious anemia and osteoporosis in 21 postmenopausal women with pernicious anemia. In the women with pernicious anemia, the bone mineral density of the lumbar spine was decrease by 16 percent compared to 24 normal postmenopausal women. Pernicious anemia is caused by B12 deficiency, and B12 is also a coenzyme in homocysteine metabolism.
Two more recent studies support the role of vitamin B12 in bone density. One appeared in the March 2003 issue of the Journal of Nutrition. In this study, osteoporosis occurred more often among women whose vitamin B12 status was considered marginal or deficient than in women with normal status. The authors concluded that vitamin B12 status is associated with bone health in elderly women.
A study done a year later in the March 2004 Journal of Clinical Endocrinology and Metabolism found the same association. The purpose of the study was to test whether women with low serum vitamin B12 levels at or below 280 (the lowest category of serum B12 levels in which the women were grouped) had a greater annual loss in total hipbone mineral density compared to women with vitamin B12 levels above 280. They concluded that low serum vitamin B12 levels are associated with increased rates of hipbone loss in older women. Finally, a study published in The New England Journal of Medicine in 1988 found that sufficient availability of vitamin B12 may be critical to osteopath activity and osteocalcin production, which are both involved in bone mineral building.
How to protect yourself
Folic acid is present in a wide variety of foods, but the most concentrated source is fresh vegetables, especially green leafy vegetables. Vitamin B6 is also widely concentrated in foods. But both of these vitamins are easily destroyed by processing and overcooking. Vitamin B12 is found only in foods of animal origin. Eating a well balanced diet of fresh, unprocessed foods, especially fresh fruits and vegetables, is the best way to get all of these vitamins.
However, in the case of a vitamin B12 deficiency, the cause is rarely a dietary deficiency. More than 95 percent of the cases of vitamin B12 deficiency seen in the United States are due to inadequate absorption of the vitamin. Although it is popular to inject vitamin B12 in the treatment of B12 deficiency, injections are not required, since the oral administration of an appropriate dosage has been shown to produce results as good as those of injectable preparations.
Vitamin B12 is necessary in only very small quantities. The RDA is 2 micrograms. However, in the treatment of vitamin B12 deficiency with oral preparation, the recommended dosage is a daily intake of 1,000 micrograms. Such large amounts are necessary because only one percent to a tenth of one percent will be absorbed. It is best to get the sub-lingual (under the tongue) form since B12 might not be absorbed in the gut, and the sub-lingual form is absorbed directly into the membranes by-passing the gut. It is also best to get the methyl-cobalamin form of B12 because it is the most easily absorbable.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.