Nutrient Requirements and Interactions Dietary a-Linolenic Acid at 1.3 g/kg Maintains Maximal Docosahexaenoic Acid Concentration in Brain, Heart and Liver of Adult Rats1

We have previously determined the dietary a-linolenic requirement for membrane synthesis in the developing animal. This study measures the dietary re quirement for maintaining normal membrane compo sition in adult rats, as determined by 22:6(n-3) (docosahexaenoic acid) concentration. Sixty-day-old rats, previously fed a diet containing both linoleic and a-lino lenic acid, were divided into nine groups, each receiving different quantities of a-linolenic acid but the same amount of linoleic acid. They were killed 4 wk after initiation of the new diet to determine the minimum quantity of a-linolenic acid required in the diet for main taining the 22:6(n-3) tissue concentration in brain (whole tissue, myelin and nerve endings), liver and heart. The minimal amount of dietary a-linolenic acid that maintained the maximal 22:6(n-3) level and minimal 22: 5(n-6) level in tissues was considered to be the dietary requirement. The quantity was found to be 1.30 g/kg diet (0.26% of dietary energy). It was lower than that found for the developing animal (0.4% of energy). At lower quantities of dietary a-linolenic acid, 22:6(n-3) was replaced by 22:5(n-6) in the organs examined, except in nervous tissue, in which 22:6(n-3) was highly preserved. J. Nutr. 123: 1313-1319, 1993.