Getting your omega-3s vs. avoiding
By now, nearly everyone has heard of the health benefits of the omega-3
fats found in fish. The most persuasive studies show that they protect
against the serious — and sometimes fatal — episodes of
an irregular heart rhythm that can cause sudden death. Other research
indicates that a diet rich in omega-3 fats may lower your risk for
heart attack and stroke.
Farm-raised salmon is one of the better sources of omega-3s. A 6-ounce
serving contains about 3½ grams which is much more than in other
popular fish. There’s no straight answer to whether farm-raised
or wild salmon has more omega-3 fat—it depends on what they eat.
Today about half of the salmon sold worldwide comes from fish farms.
Risks from PCBs
Polychlorinated biphenyls (PCBs) are oily, synthetic chemicals that
were used in electrical equipment and as additives to paint, plastics,
and other products. Unfortunately, they’re now found in today’s
farm-raised salmon. The federal government ordered industry to stop making
them in the 1970s, but they still get freshly released into the environment
from hazardous waste sites, leaks from old equipment, and incinerators.
PCBs also stick to soil and sediment and can travel long distances through
the air. They also “bioaccumulate” in fat, so concentrations
tend to be higher in animals — like salmon and marine mammals like
seals — that are further up the food chain. High doses kill fish,
and PCBs have been linked to reproductive and immunological problems
in several species of wildlife.
How great a risk they pose to human health is debated. The Environmental
Protection Agency (EPA) has classified PCBs as probably causing cancer
in humans. But several studies that have looked for a PCB-cancer connection
haven’t found one. Research has shown that babies born to women
exposed to high levels of PCBs are more likely to have neurological problems
and developmental delays.
PCBs in farm-raised salmon
The PCBs in farm-raised salmon come from the feed, which is made from
smaller fish like herring and anchovies. Previous research had hinted
at a problem, but a study in the Jan. 9, 2004, Science made
a big splash because it was much larger (700 salmon samples) and was
published in a prestigious journal. The study found that the PCB concentrations
in farm-raised salmon were, on average, almost eight times higher than
the concentrations in wild salmon (36.63 parts per billion vs. 4.75).
That was still much lower than the FDA limit of 2,000 parts per billion.
But the EPA has stricter standards for limiting exposure to pollutants
in fish. The researchers said if those guidelines were applied to farm-raised
salmon, it would trigger an EPA warning not to eat any of the farm-raised
salmon they tested more often than once a month.
Five take-home messages
What should you do? People have to balance the risks and benefits for
themselves, but here are some thoughts on farm-raised salmon:
Eating fish is generally a smart move for your health. Eating a variety
of fish should limit your exposure to things like PCBs.
- The older you are, the greater your chance for cardiovascular disease,
and the increased importance of omega-3s. That might tip the balance
in favor of farm-raised salmon. But if you’re pregnant, then
the risks from PCBs loom larger and you may not want to take any
chances, however slight. If you have a personal or family history
of cancer, you might opt to eat only one to two servings of farmed
salmon per month.
- If you’re concerned about PCBs, don’t eat the skin of
the salmon or the fat directly underneath it. That’s where the
pollutant is most concentrated. But that may make you miss out on some
- The study in Science found that the least contaminated farm-raised
salmon came from Chile and Washington State, and the most contaminated
came from Scotland and the Faroe Islands between Norway and Iceland.
So if you are worried about PCB contamination, you can ask where the
salmon came from and buy accordingly.
- The salmon industry was critical of the study in Science and
complained that it was being singled out. But nobody wants to eat PCBs.
The study should prompt the industry to look for “cleaner” sources
April 2004 Update
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