Serum levels could mean your body has more DHA than it needs, without an established level at which some kind of deficiency develops.

I’m not trying to prove a point except this: People who have no regard to dietary DHA and consume no fish don’t exhibit any of the problems claimed in articles and by nutritionists. I’ve been vegan for 20 years for example and my skin is fine, I don’t supplement DHA, I don’t have dementia or other health problems.

This contrasts pretty strongly with homocysteine/B12 deficiency or iron deficiency. There’s no good evidence that a clinical syndrome of DHA deficiency even exists. Whenever I dig into studies serum levels are all over the place.

There’s quite a lot to be suspect of here. The conclusions drawn from our limited understanding of fatty acid metabolism just doesn’t match reality.