A similarly surprising fact is the Omega-3 fatty acid actually comes from algae the fish eat. As a result there are vegan-friendly algae-derived supplements as an alternative to the popular fish oil ones.

On a brief vegetarian experiment I used a methylcobalamin sublingual B12 supplement, but it had strange and totally unique side effects. After a week of daily use, and this was consistently reproducible, my neck would become very stiff and painful to turn. I don't know why, but it didn't take much of a leap for me to connect this stuff diffusing into my system from under my tongue and the surrounding neck tissue being effected. I find it preferable to just eat sardines regularly.