Canned fish and I are friends. It's a cheap and convenient way to get good food into your system. Gotta run and forgot to pack lunch? You could do worse than a can of mackerel, an apple, and some nuts. In fact, I sometimes do that even if I don't have to rush.
Just make sure to read the ingredient labels carefully. Sometimes "tinned in olive oil" forgets to mention they also use soybean, or those sardines may have sugar in them, etc.
Another factor to bear in mind besides the oils and added ingredients: the presence of BPA (bisphenol A, a type of plastic) in the inside lining of many cans.
This applies not just to canned fish, of course, but also to things like canned tomato sauce.
Whether BPA is actually harmful to health, endocrine disrupter and so forth, is another matter - it seems current evidence is unclear about this. But if you're worried about it then it would be another factor to bear in mind when choosing canned foods.
Randy Hartnell, whose company, Vital Choice, sells products aimed at health-conscious consumers, switched last year to can linings made without BPA. It was a costly move that he figured would resonate in the niche market that buys his canned wild salmon and low-mercury tuna.
But a recent Consumers Union test detected small amounts of BPA in Vital Choice tuna, raising questions about whether it is possible to clean the food supply of the ubiquitous chemical. The consumer group also found trace amounts of BPA in baked beans made by Eden Foods, the only other U.S. company that says it has switched to BPA-free cans.
I usually avoid the stuff with added oils...most of what I have read indicates that tinned fish is actually healthiest/least processed (mackerel, herring, sardines, even Alaskan salmon -- I think it was on MDA that I read farmed salmon does not hold up as well to canning as does the fresh kind) -- good for Omega-3s, and I quite enjoy them. It's hard to find good fish, so bottom feeders like the aforementioned fish (with the exception being salmon) are a nice, sustainable, option.
i probably have water packed slightly smoked herring ["kippered snacks"] once or twice a week, accompanied by 4oz of full fat cream cheese. [makes a fast, easy, filling lunch.] they're packed in water, and a good source of omega-3. smaller, cold-water fish such as herring, sardines, etc are less likely to carry heavy metals or pcb's or other noxious substances which tend to be concentrated as they move up the food chain via successively larger fish. i haven't worried much about the heat of canning; hard to believe it's more of a problem than cooking.