Lifelong intake of flaxseed or menhaden oil to provide varying n-6 to n-3 PUFA ratios modulate bone microarchitecture during growth, but not after OVX in Sprague-Dawley rats.

Key Findings:

This study assessed diets with varying n-6 to n-3 PUFA ratio at levels attainable through healthful diet patterns in humans (10:1 or 5:1) does not cause consistent changes to the primary bone structure outcomes most commonly associated with changes to bone strength. Feeding a lower PUFA ratio (5:1 versus 10:1) by providing higher absolute amounts of n-3 (as flaxseed oil) resulted in benefits to cortical bone during growth and these benefits were sustained during periods of bone remodeling (following bone loss, OVX). However, feeding this diet (5:1 (flaxseed)) resulted in significant detriments to trabecular bone compared to 5:1 (menhaden) fed SHAM groups. In conclusion, altering the source and absolute amount of n-3 PUFA to provide varying n-6 to n-3 PUFA ratios in the diet caused differences in bone structure between groups at 3 and 6 months of age but many of these differences are not consistent. Dietary n-3 PUFA provided at two physiologically relevant levels is not an adequate strategy to protect against OVX-induced trabecular bone loss.

ABSTRACT:

SCOPE: Skeletal health is a lifelong process impacted by environmental factors, including nutrient intake. The n-3 source and PUFA ratio affect bone health in growing rats, or following ovariectomy (OVX), but no study has investigated the longitudinal effect of PUFA-supplementation throughout these periods of bone development. METHODS AND RESULTS: One month old, Sprague-Dawley rats (n = 98) were randomized to receive 1 of 4 diets from 1 through 6 months of age. Diets were modified from AIN-93G to contain a varying amount and source of n-3 (flaxseed versus menhaden oil) to provide an n-6 to n-3 ratio of 10:1 or 5:1. At 3 (prior to SHAM or OVX) and 6 months of age, bone microarchitecture of the tibia was quantified using in vivo micro-computed tomography (SkyScan 1176, Bruker microCT). Providing 5:1 (flaxseed) resulted in lower trabecular thickness and medullary area and greater cortical area fraction during growth compared to diets with a 10:1 PUFA ratio, but many of these differences were not apparent following OVX. CONCLUSION: PUFA-supplementation at levels attainable in human diet modulates some bone structure outcomes during periods of growth, but is not an adequate strategy for the prevention of OVX-induced bone loss in rats.