If DHA is harmful, why did evolution create a dedicated transporter to bring it into the brain?
I’ve been reading Ray Peat’s arguments against omega 3s, and there’s one point I can’t reconcile with modern lipid biology.
Peat argues that DHA is inherently harmful because it’s highly unsaturated and readily undergoes lipid peroxidation, producing damaging oxidation products.
However, from what I’ve read, the body appears to actively and selectively transport DHA into the brain. The main omega 3 in the brain and retina is DHA, not EPA. DHA can circulate as lysophosphatidylcholine-DHA (LPC-DHA), and the blood brain barrier contains a specific transporter, MFSD2A, that efficiently transports LPC-DHA into the brain. EPA, on the other hand, crosses the blood brain barrier much less efficiently and accumulates very little in brain tissue.
So this doesn’t seem like passive accumulation, the body appears to have evolved a dedicated mechanism to deliver DHA specifically to the brain.
If DHA is primarily harmful because it’s so susceptible to oxidation, why would evolution develop a specialized transporter to concentrate it in one of our most important organs instead of using more oxidation resistant fats?
Is the current understanding simply that DHA’s functional benefits (membrane fluidity, neuronal signaling, retinal function, etc.) outweigh its oxidation risk, with antioxidants and repair systems managing the downside? Or is there another explanation that I’m missing?