The impact of omega-3 fatty acids on osteoporosis.

The essential polyunsaturated fatty acids (PUFAs) comprise 2 main classes: n-6 and n-3 fatty acids. The most common source of n-6 fatty acids is linoleic acid (LA) which is found in high concentrations in various vegetable oils. Arachidonic acid (AA), the 20-carbon n-6 fatty acid, is obtained largely by synthesis from LA in the body. The n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic (DHA) are found in fish and fish oils. Long-Chain polyunsaturated fatty acids (LCPUFAs) and lipid mediators derived from LCPUFAs have critical roles in the regulation of a variety of biological processes including bone metabolism. There are different mechanisms by which dietary fatty acids affect bone: effect on calcium balance, effect on osteoblastogenesis and osteoblast activity, change of membrane function, decrease in inflammatory cytokines such as interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha), modulation of peroxisome proliferators-activated receptor gamma (PPARgamma). Animal studies have shown that a higher dietary omega-3/omega-6 fatty acids ratio is associated with beneficial effects on bone health. In spite of increasing evidence of the positive effects of dietary fats on bone metabolism from animal and in vitro studies, the few studies conducted in humans do not allow us to draw a definitive conclusion on their usefulness in clinical practice.