Exactly! Brain and bone marrow are ... in addition to fish body oil .. the richest known sources of the essential fatty acid DHA, which humans cannot manufacture in their own bodies.

Nuts and oily fruits can provide short-chain fatty acids. But the long-chain essential fatty acids -- EPA (eicosapentanoic acid) and DHA (docosahexanoic acid) specifically ... are found pre-formed in nature only in animal-source fat. Long chain fatty acids are the chief constituents of our nerve cells and larger brain.

Humans may be able to synthesize DHA from plant-based alpha-linolenic acid (ALA or LNA) eg. from oil-bearing seeds, but the process is inefficient and incomplete. It's bioligically simpler to acquire DHA directly from animal-source fat. In fact humans are born lacking the desaturase enzymes necessary for the conversion of plant-based fatty acids -- human-breast milk is necessarily rich in pre-formed DHA. As well, a substantial percentage of human adults are deficient in these enzymes. This would suggest that the ability to synthesize DHA (and EPA) from plant-based fatty acids is not part of natural human evolution. Rather, it's an inefficient survival adaptation to the lack of pre-formed long-chain fatty acids from animal sources.


Doreen