The effect of long chain polyunsaturated fatty acids on bone throughout the lifespan: An investigation of bone mass and its regulation by bone and mineral metabolism

The pathology of osteoporosis is low bone mass potentially leading to fractures. Dietary long chain polyunsaturated fatty acids (LCPUFA), including arachidonic acid (AA), eicosapenaenoic acid (EPA) and docosahexaenoic acid (DHA), influence bone mass, mineral content and metabolism. The amount of each of these LCPUFA required throughout the lifespan to optimize bone health is unknown. To further understand the effects of specific LCPUFA in infant bone growth, dietary AA and DHA in varying amounts at a 5:1 ratio were added to formula and fed to male piglets for 15 d. Bone mass, as measured by dual energy x-ray absorptiometry (DXA), was higher with 0.5 and 0.1 g/100 g of fat as AA and DHA than in the unsupplmented group. These effects were not explained by changes in bone (including tibia prostaglandin E2) or mineral metabolism. Higher amounts (1.0 g AA and 0.2 g DHA/100 g of fat) reduced bone resorption, altered femur Zn and Ca content, but did not affect bone mass. To assess whether other life stages were affected by specific LCPUFA, a long-term rat study was conducted. The effects of an EPA diet (0.5 g EPA, 0.1 g AA and 0.1 g DHA/100 g of fat) or an AA diet (0.5 g AA, 0.1 g EPA and 0.1 g DHA/100 g of fat), to reflect current recommendations and/or intakes, on bone mineral content (BMC) and area (BA) using DXA and femur morphometry were compared at 3 time points (early, mid and late) from weanling to maturity (over 49 wk) in male and female rats. Compared to control, dietary EPA, regardless of when supplemented, decreased femur BA in males and decreased urinary Ca in females. At the levels studied, neither AA nor EPA affected BMC, bone resorption or femur prostaglandin E2. Compared to control, males fed AA mid or continuously had wider femur neck and head widths, respectively. Femur Mg, Zn and P content, but not Ca, were altered by dietary AA and EPA. The effects on Zn and P content were gender specific. Dietary AA or EPA with DHA affect mineral metabolism and bone size or mass at different stages in the life cycle. Whether higher neonatal bone mass and elevated femur neck and head width during maturity offer protection against osteoporotic fracture requires clarification.