For the past year or so, I have taken cod liver oil for omega-3 fats. Then I read the recent paper that said there may be too much Vitamin A in cod liver oil. A few weeks ago I switched to fish oil.
From the beginning, something didn't seem right. I started to feel sluggish. Last week, I tried some days with fish oil and some days without. Whenever I skipped the fish oil, I usually felt better the next day.
I'm not exactly sure why I did okay on cod liver oil but not fish oil. The Weston Price Foundation recommends cod liver oil and not fish oil, though I'm not exactly sure why.
I checked out a couple forums where people documented their experiences with fish oil. The differences were pretty startling. Some people did great with fish oil - smoother skin, more energy, etc. Others did worse - itching skin, sleepiness, etc.
It's strange that this supplement that is supposed to be beneficial to all could have such different impacts. Maybe other nutrients are needed in the diet to properly metabolize the omega-3 fats in fish oil. Maybe cod liver oil has those other nutrients.