Vitamin E may be bad for bones

Vitamin E decreases bone mass by stimulating the generation of bone-degrading cells, reports an article published online this week in Nature Medicine. As vitamin E containing supplements are widely consumed, these results may have public-health implications. Bone strength is maintained by the balance between bone-forming cells, called osteoblasts, and bone-degrading cells, called osteoclasts, which are formed by the fusion of precursor cells. Although the role of fat-soluble vitamins such as vitamin D in maintaining bone strength is well known, the role of vitamin E, or alpha-tocopherol, is less clear. Early studies had shown a positive effect of vitamin E on bone. This effect was proposed to be dependent on the antioxidant properties of alpha-tocopherol. By contrast, Shu Takeda and his colleagues report that mice deficient in an alpha-tocopherol transfer protein, a model of vitamin E deficiency, have high bone mass as a result of a decrease in bone degradation. The team found that alpha-tocopherol stimulated the fusion of osteoclast precursor cells, independently of its antioxidant capacity, by inducing the expression of a series of molecules crucial for osteoclast formation. Moreover, healthy mice or rats fed a diet with an amount of alpha-tocopherol similar to what is found in supplements consumed by many people lost bone mass, highlighting the potential relevance of these findings to human health.