Yesterday I was asked to weigh in on a simple question that happens to have a complicated answer-- the best kind! The question: If you're trying to get the health benefits of increased dietary omega-3 fatty acids, is fish oil supplementation as good as eating oily fish?
Considering that several of the studies that support omega-3 benefits were done using fish oil supplementation, I suspect that the quick answer is "fish and fish oil are similar." At least as far as we can currently tell.
But the real answer depends on a number of things:
1. The ratio of omega-3 to other omega family fatty acids.
Because of the mechanism of fish's omega-3 benefits, it's necessary for omega-3 molecules to greatly outnumber competing omega molecules. (Omega-6 fatty acids are necessary, but are common in the Western diet.) Some supplements expressly include these competing fatty acids, which may decrease the potential for the omega-3 to do any good. Farmed fish may also be lower in omega-3 than their wild counterparts. (The overall ratio of omega-3 to other fats in your diet is also very important.)
2. Content of toxins such as heavy metals, PCBs, and other chemicals that may negate the long-term good stuff associated with omega-3.
Ocean waters contain some level of these contaminants, and so therefore do fish. The higher up the food chain the fish is and the older it is, the more they have tended to accumulate these toxins. For example, a tiny, short-lived, plankton-eating sardine will be safer to eat than a huge, long-lived, carnivorous tuna.
Supplement makers put their fish oils through a chemical purification process that reduces these contaminants, but they may also concentrate the fish oil, which would also concentrate any toxins present. An unconcentrated, well-purified supplement would probably have fewer toxins than carnivorous fish from the ocean.
3. What kind of processing the oil has undergone.
For fish, this is not of great concern except for cooking. Suffice it to say, deep frying your fish in peanut oil or being lavish with the butter may not produce the health benefits you want from fish. Eating raw fish would not alter the oil content, but comes with concerns of food-borne illness.
For supplements, processing is more industrial. Oil may be chemically cleaned, distilled, converted and re-converted. This processing should leave the oil safe to ingest and the omega-3 content intact, but only if done correctly. As fish oil gains in popularity as a supplement, some companies will no doubt be tempted to cut corners, to the detriment of consumers. Doing a little brand research may be helpful.
4. What else you are eating.
One of the benefits of reaching for whole foods rather than a supplement is that whole foods come with other nutrients. Fish is low in saturated fat and contains a large percentage of protein, which helps you feel satisfied after a meal. For example, 3 oz of cooked mackerel comes with 22 g of protein and nearly 2 g of minerals. Plus, if you are eating a piece of fish, you may be replacing something else on your menu that is not as nutritious.