Flaxseed oil supplementation increased plasma eicosapentaenoic acid proportion, but did not stimulate ketogenesis in healthy young and older adults

Introduction: Cognitive decline in the elderly is associated with lower brain glucose uptake. Ketones are synthesised from acetyl CoA generated from fatty acid βoxidation and are the main alternative fuel to glucose in the brain. Among long chain fatty acids in the diet, alpha linolenic acid (ALA) is one of the most easily oxidized and may thus stimulate ketone production. Objective: To determine if flaxseed oil supplementation, enriched in ALA, could stimulate ketone production in healthy young (between 18 and 30 years old; n of 10) and older (over 65 years old; n of 10) adults. Methods: Plasma ketones (βhydroxybutyrate (βOH) and acetoacetate) were analysed during fasting and every hour for 6 h following breakfast, before and after a 4 week flaxseed oil supplementation (4 g per d of flaxseed oil, corresponding to 2 g per d of ALA). Plasma fatty acid composition was determined by gas chromatography. Results: At baseline, older adults had 50 percent higher total plasma fatty acid concentrations (p of 0.04). Older adult’s baseline plasma βOH concentrations were 50 percent  higher compared to the young (p of 0.04), however, postprandial production remained identical in both groups. After flaxseed oil supplementation, plasma ALA level was doubled (p of 0.01) and EPA level was increased by 50 percent  (p of 0.01) in both groups, whereas DHA content remained unchanged. Flaxseed oil supplementation did not significantly modify baseline ketone levels and postprandial production. Conclusion: Flaxseed oil supplementation is not an ideal candidate for stimulating ketogenesis. Despite higher plasma fatty acid and βOH concentrations at baseline, aging did not alter ALA and ketone metabolism. However, flaxseed oil positively impacted plasma fatty acid profiles by increasing ALA and EPA plasma concentrations. (Authors abstract)