Fish – Catholic Carnivore

Last update: 19 November 2020

Fish are the major dietary source of the polyunsaturated n-3 fatty acids EPA and DHA. This makes them a potent tool in managing your n-3 to n-6 fatty acid composition, which you may want to do to improve your health^1,2,3. However, not all fish are created equal, and farmed fish have distinct lipid profiles from wild fish, where the farmed varieties have much more linoleic acid^4,5,11. The total amount of fat⁴ needs to be considered as well, since all the fish in the world won’t make a difference if they are too lean.

In general, I think it’s vastly preferable to eat wild fish over farmed fish. Sometimes, fish are labelled as to their origin (farmed or caught), but often they are not. Distinguishing them can be a problem, one possible solution to which would be to look at which fish species are mentioned in aquaculture analyses. For example, in one document about Polish aquaculture⁶ lists 29 fish species produced, among others carp (several species), trout (several species), sturgeon, salmon (two species), pike, catfish and tench. I wouldn’t eat any of the fish on that list regularly, on account of them linoleate content, since anything I find in the shops is likely to originate from these fish farms.

Specific recommendations are difficult to give, since type of aquaculture and access to global food supply differ between regions. However, two fish species that I’ve never heard about being farmed for human consumption are sprat⁷ and herring^7,8 (do correct me if I err). Given the publications on the matter of fatty acid profiles^9,10,11, mackerel also seems very likely not to come from farms.

A frequent objection to fish consumption is the danger of methylmercury poisoning. While this is a real concern¹², they need not be eaten in such amounts as to cause significant risk – 50-100 grams fatty fish per day is probably more than enough. Furthermore, bioavailability¹³ and amount of mercury vary considerably across particular fish and locations^14,15. Small fish, low on the trophic level (such as sprat and small herring), tend to have less mercury¹⁵.

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