Fish is a very healthy food, but some cooking methods make it healthier than others.
This article reviews the best cooking methods for fish. Read on www.healthline.com/nutrition/healthiest-way-to-cook-fish
I haven’t read much over the years about the effect of different cooking methods on the nutritional quality of fish. I think the general assumption has been that fish cooked anyway is always better than no fish at all. I think there’s actually evidence that fish may be detrimental before it is even cooked if the polyunsaturated fatty acids in it have begun to go rancid. However, that is another story for another day.
This story is about whether fish is susceptible to the same issues that affect other animal foods in the course of certain types of cooking. For example, it is well known that grilling meat over an open flame produces carcinogenic compounds and that excess consumption of meat prepared this way is associated with a higher risk of cancer. There’s no compelling research to prove that the same thing with fish. The grilling of fish over an open flame does produce the same carcinogenic compounds, so the absence of any research about the health effects is probably due to the fact that the subject has not been studied extensively.
Although fish consumption has increased significantly in the United States over the past couple of decades, most of it is currently consumed after being prepared deep-fried and a significant amount of the rest is grilled. Much of what is on sale at many markets smells rancid. I’ll have to see if there’s any research indicating what percentage of fish for sale on the open market or rancid at the time of sale. Sushi, which would seem to sidestep all of these issues. It is not cooked at any temperature. And, it doesn’t ever smell rancid even at a low to medium end restaurant. However, the reason for that is is that most of the sushi fish sold in the United States is heavily preserved.
Here’s a few quotes from the article about the detrimental effects of deep frying fish:
In fact, one study found that frying tuna decreased the amount of beneficial omega-3 fatty acids by 70–85%.
Other nutrients may be at risk too, as one study found that frying salmon reduced the amount of vitamin D it contained by half (￼.
The high temperatures of frying may also cause more of the harmful compounds HAs, PAHs and AGEs to form.
I would recommend getting your fish from the farmers market from unknown source and preparing at home using methods like baking, sautéing, poaching, etc.