Long story short,
In Mediterranean and Scandinavian diets (for example) they eat lots of fish. More than, what is recommended in (most countries in) Europe, 1 or 2 times a week, max. Why is this a recommendation that pops up everywhere, while countries who seem to have a much higher average life-span generally eat much more fish (the 9 places in the world where people live the longest seem to eat way more fish)?
I know this is not a direct correlation — it definitely includes many other factors as well and it’s also all about balance — but the point is, why is the recommendation made in (quite a lot) Western countries to eat fish max. twice a week while other countries seem to ignore this recommendation and claim the opposite by stating that eating fish everyday is really good for your health?
>recommended 1 or 2 times a week, max
This isn’t a thing. The FDA recommends eating AT LEAST 8 ounzes (2 servings) of fish per week. The 2-3 servings max is only for small children and pregnant women.
Mercury is the big debate when it comes to fish. Some species of fish, most notably Tuna is quite high in Mercury comparably to a lot of smaller fish like Sardines, Mackerel and Salmon. Those fish should be limited to 1-2 times per week. The “safe” fish you can eat without much worry.
FDA recommendations on fish:
https://www.fda.gov/food/consumers/advice-about-eating-fish
Recent post discussing Mercury in Salmon vs. Tuna:
https://www.reddit.com/r/nutrition/comments/xil0cn/is_10oz_of_fish_per_day_too_much_if_it_is_just/
Tony Robbins found out what happens when you eat too much fish. His mercury levels got so high that the authorities were suspicious that his wife had poisoned him!! He is lucky he survived. (He tells this story in the film “Eating our Way to Extinction”.)
But that being said, just because there is an unsafe upper limit doesn’t mean that there isn’t a safe lower limit.
Eat all the smaller fish you want, like sardines, and also salmon, and so on, to avoid too much mercury. However, there can be issues with farm-raised for some fish, not only ecologically (they have to dump a ton of anti-biotics into the water) but also health-wise regarding the fish (overcrowded fish enclosures with poor fish health and poor nutrition). So if you want to buy and eat anything farm-raised, check into the situation with the particular species. Some farm-raised might be ok, like Tilapia I think does OK crowded together (though some claim tilapia have low nutrition compared to others).
In a cleaner world, fish is one of the best. But its still good, just be careful of a few things, including how they are caught or other issues: https://www.greenpeace.org/usa/oceans/sustainable-seafood/red-list-fish/