The largest survey yet of pollutants in salmon, reported in the January 9, 2004 issue of Science, clearly indicates that because of the feed they receive, farmed fish have much higher levels of carcinogenic pesticides (specifically polychlorinated biphenyls or PCBs, and two other organochlorine compounds, dieldrin and toxaphene) than wild caught salmon.
The massive study, funded by the Pew Charitable Trusts' Environment program, was conducted by six scientists who analyzed about 700 salmon from around the world for more than 50 contaminants. For 13 of 14 of the organochlorines tested, farmed salmon were more contaminated than wild ones. Levels were highest in European farmed salmon, followed by those from North America. Chilean farmed salmon were the cleanest. The oil and meal the farmed salmon were fed exhibited a similar pattern.
For the most contaminated fish—from farms in Scotland and the Faroe Islands—a quarter of one serving (55 grams of uncooked salmon) per month was the maximum amount that could be eaten before boosting cancer risk, according to EPA guidelines. One half-serving (110 grams) of farmed salmon from Canada or Maine could be eaten per month without adding to significant risk, and one serving (220 grams) per month would be acceptable for fish from Chile or the U.S. state of Washington.
In comparison, according to EPA guidelines, it is considered safe to eat one serving (220 grams) of some types of wild salmon from Alaska or British Columbia eight times a month, which would meet the American Heart Association recommendation to consume 168 to 336 grams of fatty cold water fish per week.
One reason consumers may become confused by the news coverage of this issue is that the PCB levels determined by the U.S. Food and Drug Administration (FDA) to be safe for sale in supermarkets are 40 times higher than those the EPA has determined is safe in recreationally caught fish. This is due, in part, to the fact that the EPA looks solely at health risks while the FDA considers food safety and nutrition.
Despite study authors' warning that consuming more than one meal of farmed salmon per month may hike the risk of cancer, other experts claim the risk is outweighed by the benefits of eating farmed salmon, especially for individuals with cardiovascular disease since consumption of the omega-3 fats found in fatty fish reduces the risk of sudden death after a heart attack. We disagree. As explained earlier on the World's Healthiest Foods, it is not merely amount of omega 3 fats present in these fish that must be considered, but the ratio of omega 3 to omega 6 fats, since both types of fats rely on the same enzymes to be used within the body. Farm raised fish contain such high levels of omega 6 fats that the amount of usable omega 3s they provide is dramatically less than their wild counterparts.
We strongly recommend that pregnant women, nursing mothers and women of childbearing age avoid eating all farm raised fish including salmon. Organochlorines damage the developing endocrine system, immune system, and brain. Once consumed, these toxic compounds are stored in body fat where they can remain for decades until they are passed to a woman's fetus during pregnancy or excreted in her breast milk.
Practical Tip: How to get wild salmon
While scientists continue to debate the issue, and fish farmers try to find a feed with low contaminant levels, the World's Healthiest Foods urges all consumers to use the data on this website to make informed decisions and to select the cleanest fish possible. For now, farmed fish are not a healthy choice. It is not recommend that we eat farmed salmon more than once a month.
Fresh Salmon The season for fresh wild salmon begins around late February so ask your fishmonger about its availability. Salmon will become more affordable in the succeeding months as increasing numbers return to fresh water to spawn. Wild salmon is a great addition to your menu because it is rich in essential omega-3 fats and also is a very good source of high quality protein. While it is difficult to get fresh wild salmon during certain times of the year because the season for wild salmon begins in late February and ends in November, frozen or previously frozen salmon is available. If you don't see previously frozen salmon on ice or frozen salmon at your local fishmonger's, ask if it can be ordered for you. Frozen salmon may also be ordered on-line. Just enter "Frozen wild salmon" into your Search engine, and you'll find a number of suppliers. While King salmon is often considered the best tasting salmon and also has the highest levels of omega-3 fatty acids, coho salmon is also very good.
Canned Salmon Another way to add wild salmon to your menu is to purchase canned salmon, which is available year round and is much less expensive than fresh or frozen salmon. Most all canned salmon is wild salmon, and this is indicated on the label. Canned salmon offers some additional advantages as well. It is usually packed in its own oil, so you can benefit from greater quantities of omega-3s. Canned salmon also includes the bones, which are safe to eat since they soften during the canning process. This increases its calcium content so that a 3 ounce serving generally contains as much calcium as a glass of milk! Low-salt or no-salt varieties of canned salmon are available for those concerned about their salt intake.
Smoked Salmon Smoked wild salmon is also available year round, but because the smoking process reduces its omega-3 content by 75% and also deposits carcinogenic compounds on the salmon, we do not recommend eating smoked salmon often.
Lox Although only very lightly smoked, this type of prepared salmon contains large quantities of preservatives including sodium nitrate. Since frequent consumption of sodium nitrate has been linked to colon cancer, we do not recommend eating lox often.
Stokstad, E. Salmon survey stokes debate about farmed fish. Science, vol 303, p154-5, January 9, 2004.
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