Author claims PCB contents of wild and farmed Salmon are similar; claim is dubious, and article ignores nutritional distinctions between farmed and wild Salmon
by Craig Weatherby
A Cooking Light magazine article posted on CNN.com triggered some queries to our inbox, regarding the relative safety of wild and farmed Salmon.
The article’s author states that, contrary to the findings of all of several prior studies, new evidence shows that farmed Salmon is about as low in PCBs as wild Salmon.
We could not corroborate the author’s claim, whose source is not cited.
Every study we can find reports that farmed Salmon is five to 10 times higher in PCBs, compared to wild Salmon.
In 2004 and 2005, Canadian scientists published two studies, which generated the first big headlines on the topic of PCBs in farmed Salmon (Hites RA et al 2004; Foran JA 2005).
As they wrote, “Even the least contaminated farmed Salmon… had significantly higher contaminant loads… than wild Salmon” (Hites RA et al 2004).
And subsequent studies have found similar purity gaps between farmed and wild Salmon, which are attributable to the much greater amounts of fish fat in the diets and bodies of farmed Salmon (PCBs and other persistent organic pollutants accumulate in fish fat over time).
But even if the Cooking Light article is right, and a new study reported finding lower PCB levels in farmed Salmon than detected previously, wild Salmon remains the healthier choice.
Farmed Salmon is higher in PCBs... but not unsafe in moderation
All Salmon are very low in mercury compared with other fish. And wild Salmon is low in PCBs, compared with meats and dairy.
But farmed Salmon is high in PCBs, relative to wild Salmon and all other animal foods.
Even if the Cooking Light article is right about farmed Salmon getting cleaner—and we'll remain skeptical until we see Ms. Callahan's evidence—the vast majority of available evidence will still suggest two things:
- People can eat as much wild Salmon as they want, very safely.
- People probably should not eat farmed Salmon more than twice a week.
These were the key conclusions of a recent analysis of farmed versus wild Salmon (Dewailly E et al 2007):
- “…while some differences were observed between farmed and wild fish… overall the concentrations of key contaminants were low, such that the regular consumption of these fish [farmed and wild Salmon] would not cause significant health risks.
- “…eating farmed Salmon twice a week would likely… approach the lowest… [tolerable daily intake level for PCBs]… established by the WHO [World Health Organization].”
While farmed Salmon are not as healthful as wild Salmon, its higher PCB content is probably less important than its inferior nutritional profile.
Article claims PCB levels in farmed Salmon have fallen
Given that all of the voluminous data we’ve seen on the subject shows that farmed Salmon is higher in PCBs, we were surprised to read the following in an article by Maureen Callahan of Cooking Light magazine, which was posted at the CNN.com web site earlier this week:
“…two more recent studies, one on farm-raised Salmon and the other on wild, found that both harbor similar levels of this pollutant. The first study, done with Chilean- and Canadian-farmed salmon, found an average of 11.5 parts per billion PCBs. The second, conducted by the Alaska Department of Environmental Conservation [DEC], sampled 600 wild salmon from the Gulf of Alaska and the Bering Sea, and found 8.2 to 10 parts per billion PCBs.” (Callahan M 2008)
We have a copy of the Alaska DEC study, which dates from 2005, and Ms. Callahan is correct that it found PCB levels in wild Alaskan Salmon that averaged 8.2 to 10 parts per billion.
But all other studies we can find reported PCB levels in wild Alaskan Salmon that averaged 5 PPB.
And we can find no study that reported levels of PCBs in farmed Salmon lower than 20 to 50 PPB.
Does the omega imbalance in farmed Salmon matter more than its PCB count?
If Ms. Callahan is right, and a new study found substantially lower levels of PCBs in some farmed Salmon, this would not come as a shock.
The bad publicity that followed repeated findings of higher PCB levels in their fish led Salmon farmers to substitute grains and vegetable oils for some of the fish meal and fish oil they’d been feeding their Salmon.
And a grainy, seedy feed will reduce PCB levels in farmed Salmon.
However, this change just shifts farmed Salmon consumers from a very warm frying pan (minor toxin risks) to a hot fire (major nutrition-related risks).
By feeding farmed Salmon grain and seed oil instead of fish and fish oil, fish-farmers reduce their product’s omega-3 content and increase its omega-6 fatty acid content: a shift that worsens the omega-3/omega-6 imbalance typical of American’s diets, which promotes cancer and America’s most common chronic diseases.
For more on the omega-3/omega-6 imbalance in farmed Salmon, see “FAQ: Salmon Fact Muddies the Nutritional Waters.”
Article offers a sound assessment of PCB dangers in all Salmon
Ms. Callahan’s article did perform one service: it emphasized that the even the higher levels of PCBs that most studies find in farmed Salmon are probably not unsafe.
Without doubt, it makes sense to minimize one’s intake of contaminants such as PCBs, so we make no apologies for the fact that research overwhelmingly gives wild Salmon the purity advantage.
But as we wrote back in 2005, the science on the subject persuaded us that even the higher levels of PCBs in farmed Salmon probably do not outweigh the benefits of its omega-3s (see “Magazine fans erroneous salmon fears”).
So, we agree with the researchers quoted in Ms. Callahan’s article:
- “It's important to realize that the amount of PCBs being talked about is very small, says Cornell University seafood specialist Ken Gall, who has studied fish safety issues for 22 years. ‘High doses of PCBs, like the kind of contamination that occurs with an industrial accident, can be dangerous," Gall says. "But it's uncertain whether the tiny amounts of PCBs found in many foods such as fish, meat, or milk can cause cancer’” (Callahan M 2008).
- “Most health experts feel the health benefits of salmon far outweigh the risk posed by minute levels of PCBs. William Connor, M.D., a professor of medicine at Oregon Health and Science University, in Portland, who has spent most of his career studying the health benefits of the omega-3 fats found in salmon, says he has no qualms about recommending farm-raised salmon. ‘I would rather my patients not miss out on the benefits of salmon, a fish with some of the highest levels of heart-healthy omega-3 fats around, than fear PCBs,’ he says” (Callahan M 2008).
What’s the evidence that these scientists are correct?
EPA guidelines exaggerate PCB risks, ignore omega-3 rewards
While contaminants are a legitimate concern, modern technology is capable of identifying amounts of these substances in the parts per trillion range.
Calculating risks from PCBs is a tricky proposition, given the paucity of data, but everyone seems to agree that the U.S. Environmental Protection Agency (EPA) is way off base in its PCB-intake advice.
The EPA sets the maximum safe level for PCB content in foods at 6 parts per billion: a concentration 300 times lower than the lowest dose at which subtle health effects have been seen in young laboratory monkeys.
In contrast, the U.S. FDA sets the maximum safe level for PCB content in foods 333 times higher than the EPA’s level, at 2,000 parts per billion.
And Health Canada (that nation’s equivalent to the U.S. FDA) sets its maximum safe level for PCB content in foods 50 times higher than the EPA’s.
In their recent critique of the studies that drew the media’s attention to the issue of PCBs in farmed Salmon (Hite RA et al 2004; Foran JA et al 2005), Canadian scientists noted serious flaws in the EPA’s method of calculating harm from PCBs:
“The major difference between our studies lies with the method used for assessing health risks. Foran et al. calculated quantitative estimates of cumulative carcinogenic risks for 11 contaminants measured in salmon using the cancer slopes factors developed by the U.S. EPA (2005).… [the EPA’s]… approach… is not appropriate for the type of carcinogens [i.e., PCBs] found in Salmon.…”
And the Canadian scientists added that EPA doesn’t take into account the health benefits of eating Salmon: a mistake not made by scientists we cited previously, and echoed by a report from scientists working for the State of Alaska.
Alaskan scientists attack EPA’s one-sided risk analysis
The Alaska Division of Public Health (DPH) issued a report on PCB levels in wild Salmon, in which they made a cogent critique of the U.S. EPA’s guidelines for PCB intake:
- “EPA cancer guidelines… do not take into account the growing body of research showing that fish consumption actually protects against some forms of cancer (Terry et al, 2003). We are concerned that populations who decrease their level of fish consumption might actually experience an increased incidence of cancer.
- “The EPA [maximum food-content] dose for PCBs… incorporates a 300-fold safety factor below the lowest dose at which subtle health effects have been seen in the offspring of laboratory monkeys fed PCBs.
- “…the Alaska Division of Public Health continues to recommend the unrestricted consumption of fish caught from Alaska waters, including… Salmon."
- “…pesticides tested were present… [in wild Salmon] at low levels or were not detected, and were far below EPA guidelines for unrestricted consumption…”
- “In developing public health advice about the dietary intake of fish, it is crucial to consider both the benefits and the risks of fish consumption. [Salmon] are a very nutritious protein source that is low in saturated fat, providing essential fatty acids, antioxidants and vitamins. Alaska Salmon and other fatty fish are excellent sources of omega-3 fatty acids, which provide many health benefits including protection from diabetes and cardiovascular disease, and improved maternal nutrition and neonatal/infant brain development.”
- “When evaluating the health implications of reduced fish consumption, it is also necessary to consider the health risks of alternative replacement foods. The market foods that often replace locally harvested fish [wild Salmon] are high in saturated fat, vegetable oils, and carbohydrates and often lower in nutrient value (Receveur et al, 1997). Diets high in saturated fat and carbohydrates are strong risk factors for a number of chronic diseases such as heart disease, diabetes, and cancer.”
It is of course wise to minimize intake of all contaminants, and by this standard, wild Alaskan Salmon is a smarter choice than farmed Salmon.
But wild Alaskan Salmon offers an even bigger advantage over farmed Salmon, in the form of a far better omega-3/omega-6 balance, and much more vitamin D.
And let’s not forget culinary considerations. Every species of wild Alaskan Salmon offers a distinctive texture and flavor … and each is decisively superior to its farm-raised cousins!
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