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B. A. WATKINS, Department of Food Science, Lipid Chem. & Molecular Biol. Lab., Purdue University, 1160 Food Science Building, West Lafayette, IN 47907-1160 and M. F. Seifert, Department of Anatomy, Indiana University Purdue University Indianapolis, School of Medicine, Medical Science Building 259, Indianapolis, IN 46202.

Growing evidence from research on dietary lipids, genisten and vitamin E indicates that these dietary factors benefit skeletal health. Investigations in laboratory animals demonstrate that n-3 fatty acids and conjugated linoleic acids (CLA) alter bone prostaglandin E2 (PGE2) production, serum biomarkers of bone formation and histomorphometric values for bone modeling. Human clinical trials and epidemiological studies show that diets providing sources of phytochemicals ("limiting dietary components") reduce bone mineral loss and are associated with a lowered incidence of osteoporosis. Osteoporosis, osteoarthritis and inflammatory joint disease afflict millions of people. Inflammatory cytokines inhibit chondrocyte proliferation and induce cartilage degradation. This response, in part, is mediated by PGE2. Excess production of PGE2 has been associated with the loss of bone and proteoglycans in osteoporosis. Conversely, lower concentrations of PGE2 positively influence the IGF-I/IGFBP axis to promote bone and cartilage formation. Studies in laboratory animals have shown that dietary lipids can alter the fatty acid composition and local production of eicosanoids and skeletal growth factors in different compartments of bone. Presumed changes in bone cell and chondrocyte functions are thought to influence bone modeling. Interestingly, the bioactive fatty acids, n-3 polyunsaturates and CLA isomers, may compliment the action of phytochemicals (genistein) to maintain bone mass. We hypothesize that genistein and bioactive fatty acids influence the activity or gene expression of cyclooxygenase enzymes to reduce bone mineral loss. New research suggests that several phytochemicals work synergistically on key enzymes that alter cellular metabolism and reduce risk of chronic disease. The focus of this presentation will be to summarize findings of dietary lipids and phytochemicals on bone metabolism in animals, to review the literature on human studies and to discuss new opportunities for research in this area.