When it comes to fish oil in particular, that isn't necessarily the case. Fish Oil is extremely sensitive to oxidation, and will become rancid quite easily, and many brands will gladly sell you oxidized oils.

As for picking a good brand that's good and not unnecessarily expensive, I would recommend watching this video.

Whatever you go with, be sure to pop open at least one capsule to smell and taste the oil to ensure it's good. If it smells rotten or oxidized (like an acrid oil similar to furniture linseed oil), then I wouldn't recommend taking it.

Personally, I would recommend incorporating more fish into the diet instead of taking a fish oil supplement, but that's just me.

Also @iLoveFishing@lemmy.today