02/04/2004
To Eat or Not to Eat?
After last week’s column on food pyramids, notably Walter Willett’s Healthy Eating Pyramid, I’m hooked on food. One of the foods that Willett and many others recommend is fish, especially fish with high amounts of omega-3 fatty acids, which protect against heart disease. On the other hand, there’s concern about mercury and other toxins concentrating in fish such as tuna and salmon that are at or near the top of the food chain. As a result, we’re being advised to exercise discretion about the amounts and choices of fish that we consume.
Looking back, I certainly wasn’t limiting my fish intake when lunching in the cafeteria at UMDNJ Robert Wood Johnson Medical School, where I went after retiring from Bell Labs in 1989. For a decade or so, I averaged some 3-4 tuna, lettuce and tomato on whole-wheat sandwiches a week. At the time, I thought I was being quite virtuous in choosing such a healthy combination (you’re right, what about the mayo?). Then came all the publicity about mercury contamination.
I was encouraged by an item in the article by Brad Lemley in Discover magazine mentioned in last week’s column. The article cited a recent study involving pregnant women in the Seychelles in the Indian Ocean. The women ate an average of 12 fish meals a week without apparent harm to themselves or their children. Gary Myers of the University of Rochester Medical Center is quoted as saying they had found no evidence that the low levels of mercury in the fish were harmful.
What about salmon? I can still taste the scrumptious freshly caught salmon I had in a restaurant in Vancouver over a decade ago. Today, most of the salmon we buy at our supermarkets or get served in restaurants is of the farmed variety. Last month, a study on toxins in wild and farmed salmon was published in the January 9 issue of Science. The article, “Global Assessment of Organic Contaminants in Farmed Salmon” has six authors, the lead author being Ronald Hites at Indiana University.
The study drew immediate media attention and caused a huge controversy between environmental groups and the farmed salmon industry. Some idea of the bitterness of the controversy may be gathered from a quote I found on the Salmon of the Americas (SOTA) Web site. SOTA is a salmon industry trade organization, as is Scottish Quality Salmon (SQS), a body in Scotland that deals with quality assurance for the Scottish salmon industry. SQS is quoted to the effect that the research published in Science appears to be “deliberately misleading in the advice it gives on farmed salmon consumption.”
What caused all this controversy? The researchers analyzed salmon from Europe and from North and South America for 14 organochlorine compounds, taking special note of PCBs (polychlorinated biphenyls) and the pesticides dieldrin and toxaphene. These three compounds have been correlated with a risk of liver and other cancers. The study was initiated and funded by the Environmental Division of the Pew Charitable Trusts. As a child, I often heard mention of “the Pews”, typically in a derogatory sense. A Pew and his sons founded and/or ran the Sun Oil Company and, in my parents’ view, typified the big money interests. My parents were of the far left political persuasion, voting for Norman Thomas, the Socialist candidate for president. They would have been surprised to see the Pew Trust supporting such environmental studies.
But I digress. This study was no small endeavor. Salmon fillets were purchased from supermarkets in 16 North American and European cities including New York, Paris, Oslo, London, Chicago, Denver, New Orleans, Vancouver, Toronto, Oslo, Seattle, etc. The total was 144 filets. They also obtained and filleted 594 individual whole salmons from wholesalers. The filets were assembled in 246 composite samples for analysis, each sample consisting of three fillets from a given retailer or location. They also analyzed 13 samples of salmon feed from different outlets of the two major feed companies.
From what I’ve read, the accuracy of the data presented in Science does not seem to be in question. It’s the analysis of the data that has caused the violent reaction in the salmon industry. The data show that the amounts of toxins, notably the PCBs, toxaphene and dieldrin, are significantly higher in the farmed and supermarket salmon than in the wild salmon. There is some scatter in the data but, assuming the validity of the chemical analyses, certain species of wild salmon contain up to about 10 to 20 times less toxins than the farmed variety. It depends on the toxin and the source.
Now comes the controversial analysis. The researchers took the results and came up with a graph that appears to provide guidance as to the maximum number of meals of each source of salmon that one should eat per month to minimize the cancer risk. The controversy lies in the choice of the Environmental Protection Agency (EPA) guidelines that purportedly represent the upper limits of consumption of the toxins to keep the added risk of cancer to 1 in 100,000. The EPA guidelines are much more stringent than the Food and Drug Administration (FDA) guidelines for sale of the salmon. Depending on where I look, the FDA figures are 40 or more times higher than the EPA limits.
What are the study recommendations? You’re lucky if you frequent supermarkets in Denver or New Orleans. You can have two salmon meals a month. Hey, that’s better than buying it in Frankfurt or getting farmed fish from Scotland, where you can’t even have half a meal a month. (Now you know why Scottish Quality Salmon is so disturbed by the study.) On the other hand, if you get wild chum salmon from the British Columbia/Alaska area you can pig out on 8 meals a month. Choose wild pink or Coho salmon and you’re down in the 2-4 meals a month range, depending on the source. In general, the farmed fish from Europe is more contaminated than that from North America and South America, notably Chile.
What to do? The American Heart Association recommends we eat 168 to 336 grams of fish a week to get the benefits of those omega-3 fatty acids. The study’s recommended portion of farmed salmon from Scotland is only 55 grams per month! Not surprisingly, the average contaminant levels of PCBs, dieldrin and toxaphene in the salmon feed from Scotland are higher than the average levels in Chile and in British Columbia. Obviously, there will be a hard look at the feed ingredients. If you accept the study’s recommendations, it seems prudent to get wild salmon if available or switch to other fish. Of course, such an extensive study probably hasn’t been done on the choices you select. Excuse me, it’s time for lunch and my wife tells me I’m having toast with cream cheese and, naturally, smoked salmon! ………………
I’m back and my lunch was delicious! I was consoled after returning to the SOTA Web site. In an article dated the day after the appearance of the Science article, Michael Gallo is quoted as saying that PCBs are in all salmon and that the difference between 5 ppb (part per billion) and 30 ppb is “meaningless”. Gallo is a prominent cancer researcher at Robert Wood Johnson Medical School, where I ate all that tuna fish. According to the article, Gallo was also involved in coming up with the EPA guidelines.
Furthermore, on the Web site of the National Institutes of Health (NIH) I found a Reuters article by Merritt McKinney that includes a statement by Jeffrey Foran, the second author of the salmon study. Foran, who is the head of a Wisconsin-based group known as Citizens for a Better Environment, says that people should not interpret the study as a message to stop eating fish. He says the study was to measure contaminant levels in salmon, not to develop guidelines for fish consumption. I’m confused. A chart showing the maximum number of meals of salmon to avoid increased risk of cancer sure seems like guidelines to me.
Well, having just come through one minor and one major bout with cancer, I’m not going to worry about salmon. Actually, I’ll be in Florida for a while and, instead of salmon, I plan to pig out on grouper sandwiches. And if I run across a study on toxins in grouper, I’ll put it aside until my return to New Jersey.
Allen F. Bortrum
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