Bioequivalence of dietary alpha-linolenic and docosahexaenoic acids as sources of docosahexaenoate accretion in brain and associated organs of neonatal baboons

The dietary bioequivalence of alpha-linolenic (LNA) and docosahexaenoic aci ds (DHA) as substrates for brain and retinal n-3 fatty acid accretion durin g the brain growth spurt is reported for neonatal baboons who consumed a lo ng-chain-polyunsaturate free commercial human infant formula with a n-6/n-3 ratio of IO:I. Neonates received oral doses of C-13-labeled fatty acids (L NA*) or (DHA*) at 4 wk of age, and at 6 wk brain (occipital cortex), retina , retinal pigment epithelium, liver, erythrocytes, and plasma were analyzed . In the brain, 1.71% of the preformed DHA* dose was detected, whereas 0.23 % of the LNA* dose was detected as DHA*, indicating that preformed DHA is 7 -fold more effective than LNA-derived DHA as a source for DHA accretion. In LNA*-dosed animals, DHA* was greater than 60% of labeled fatty acids in al l tissues except erythrocytes, where docosapentaenoic acid was 55%. Estimat es using dietary LNA levels as tracees indicate that brain turnover of DHA is less than 5% per week between weeks 4 and 6 of life. For retina and reti nal pigment epithelium, preformed DHA was at levels 12-fold and 15-fold gre ater than LNA-derived DHA. Liver, plasma, and erythrocytes ratios were 27, 29, and 51, respectively, showing that these pools do not parallel tissue m etabolism of a single dose of omega-3 fatty acids. The distributions of lab eled fatty acids for LNA*-dosed animals were similar, in the order DHA > DP A > EPA > LNA, except for erythrocytes where docosapentaenoic acid predomin ated. These are the first direct measurements of the bioequivalence of DHA and LNA in neonatal primate brain and associated tissues.