BRAIN DOCOSAHEXAENOATE ACCRETION IN FETAL BABOONS - BIOEQUIVALENCE OFDIETARY ALPHA-LINOLENIC AND DOCOSAHEXAENOIC ACIDS

The dietary bioequivalence during the brain growth spurt of cr-linolen ic (LNA) and docosahexaenoic acids (DHA) as substrates for brain and r etinal n-3 fatty acid accretion is reported for the fetal baboons, who se mothers consumed a long chain polyunsaturate-free diet with a n-6/n -3 ratio of 10:1. Pregnant baboons received i.v. doses of U-C-13-label ed fatty acids (LNA or DHA), plasma was collected from mother and fetu s, and fetal brain (occipital cortex), retina. and liver were analyzed at various times post-dose. Fetal brain DHA plateaued 15-35 d post-do se with 1.6% of the preformed [U-C-13-]DHA dose recovered in the brain . In contrast, LNA-derived DHA accretion also plateaued but was 20-fol d lower. Liver and retinal results were of the same order of magnitude , but showed evidence of peaks and decline. Conversion products to n-3 long chain polyunsaturate were observed in the maternal circulation a t 1 h after administration, as was transfer of both fatty acids to the fetus. From these measurements we estimate that a dietary level of ab out 0.45% of energy as LNA is sufficient to meet the requirements of t he growing fetal brain, whereas 0.03% of energy as DHA would suffice. These data are the first direct measurements of the bioequivalence of DHA and LNA in developing primates and imply that n-3 fatty acid requi rements for the developing fetal brain can be met by attainable dietar y LNA for diets low in long chain polyunsaturates.