DEAR DOCTOR K:
You’ve written that fatty fish like salmon are a good source of omega-3 fats. Does it matter whether the salmon is farmed or wild?
Salmon and other fatty fish certainly are an excellent dietary source of omega-3 fatty acids, which lower the risk of heart disease. Many supermarkets offer both farmed and wild-caught salmon. The two types have noticeably different tastes and textures. Wild-caught also tends to be more expensive.
But is there a difference in the amount of omega-3 fats they contain? It turns out that both types provide similar amounts of omega-3s per serving, although there is more variability among salmon raised in one farm compared to another farm.
I spoke to Dr. Bruce Bistrian, professor of medicine at Harvard Medical School. He noted that in the wild, salmon eat smaller fish that are high in EPA and DHA — the beneficial, long-chain omega-3 fatty acids. Farm-raised salmon eat high-protein food pellets. In particular, farmers often feed young salmon pellets made from plant and animal sources. They then add the more expensive fish- and fish-oil-enriched pellets later in the salmon’s lifespan.
A 2014 study measured fatty acids in 76 different fish species from six regions of the United States. They found big variations in the omega-3 content in the five different salmon species tested — especially the two farm-raised varieties. The omega-3 content ranged from 717 milligrams (mg) to 1,533 mg per 100 grams of fish (equal to a standard 3.5-ounce serving).
Compared to wild-caught varieties, farmed fish tended to have higher levels of saturated fats — “bad” fats. That’s one reason to prefer wild-caught salmon to farmed salmon, but it’s not a reason to avoid farmed salmon.
Bottom line: I wouldn’t base a choice of farmed salmon versus wild salmon on the nutritional content. Instead, let affordability, availability and taste guide your choices. What’s more important is to follow the American Heart Association’s advice to eat two servings of fish a week.
Salmon isn’t the only good source of omega-3s. Other good fatty fish choices include herring, bluefish, tuna and mackerel. Sardines, swordfish and mussels also are rich in omega-3s.
Finally, be sure to keep the big picture in mind when choosing what to eat. The healthiest eating patterns include fish as well as lots of fruits and vegetables, whole grains, nuts and olive oil, with minimal amounts of meat and dairy. Studies involving hundreds of thousands of people find that folks who regularly eat these foods have lower rates of heart disease and sudden death.
With all of my adult patients, I recommend one or two meals of fish per week. I particularly urge my patients who have heart disease already, or who have many risk factors for heart disease, to follow this advice. When these people just don’t like to eat fish, I recommend taking fish oil supplements, although the evidence of benefit from supplements is less clear than from eating fish.