The answer to this is based on the fact that we probably exaggerated the benefit of taking omega 3 based things like fish or fish oil. The root of this stems from the fact that with rise in processed foods and vegetable oils we sky rocketed the amounted of omega 6 fatty acids in our diet. From a evolutionary standpoint we are supposed to have a 1:1 ratio. This created a knee jerk reaction of increasing omega 3s to balance out omega 6s.

We do this a lot in nutrition, we match excessively high amounts of something with increasing the counter. A good module for this would be Duality in our Nutrition course. We could potentially increase our omega 3 to match high levels of omega 6, or we could simply lower our omega 6 to begin with and see what happens.

Truth is that all polyunsaturated fatty acids (3, 6, 9) are molecular unstable and oxidize readily. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7517362/). We are exposing ourselves to problematic foods when we eat any excess polyunsaturated fatty acids. we need some, but abundance no. So the answer would be to lower all polyunsaturated fatty acids and getting to a normal ratio between omega 3 and 6.

If there is a risk of mercury in fish, it will not be an issue with eating fish 2-3x a week. The best defense to heavy metals is to reduce the amount in the body. If we spread out fish in take over the course of a week, we can get the necessary amount of omega 3s (along with being a good source of protein), without causing any damage to nervous tissue from mercury.