Key Findings
ALA is converted to docosahexaenoic acid (DHA) which is important for normal brain function. Data indicates that the synthesis rate of DHA from ALA is low yet plasma concentrations of DHA in vegans are only 0 to 40 percent lower than fish eaters despite having no dietary DHA. This study determined if DHA synthesis from ALA can maintain brain DHA in rats by measuring (i) brain and whole body DHA accretion, (ii) DHA synthesis rates from ALA, and (iii) brain DHA uptake rates in rats fed 3 different diets, a control diet (low n 3PUFA), an ALA diet (2 percent ALA), or a DHA diet (2 percent DHA). Rats fed ALA and DHA accreted similar amounts of brain DHA, which together with kinetic findings suggest DHA synthesis from ALA is likely sufficient to maintain brain DHA levels. This study showed that despite large differences in fatty acid accumulation in the body, rats fed a diet containing DHA or ALA making up 2 percent of the fatty acids did not have differences in brain DHA accumulation.
ABSTRACT
Docosahexaenoic acid (DHA) is important for brain function, however, the exact amount needed for the brain is not agreed upon. While it is believed that the synthesis rate of DHA from α linolenic acid (ALA) is low, how this synthesis rate compares with the amount of DHA required to maintain brain DHA levels is unknown. The objective of this work was to assess whether DHA synthesis from ALA is sufficient for the brain. To test this, rats consumed a diet low in n3 PUFA, or a diet containing ALA or DHA for 15 weeks. Over the 15 weeks, whole body and brain DHA accretion were measured, while at the end of the study, whole body DHA synthesis rates, brain gene expression and DHA uptake rates were measured. Despite large differences in body DHA accretion there was no difference in brain DHA accretion between rats fed ALA and DHA. In rats fed ALA, DHA synthesis and accretion was 100 fold higher than brain DHA accretion of rats fed DHA. Also, ALA fed rats synthesized approximately 3 fold more DHA than the DHA uptake rate into the brain. This work indicates that DHA synthesis from ALA may be sufficient to supply the brain. (Authors abstract)
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