Pollutants in Salmon and Our Own Fat

Image Credit: Sharon Mollerus / Flickr. This image has been modified.

Salmon May Be the Greatest Source of Dietary Pollutants

In my video Diabetes and Dioxins, I explored a nationwide study that found a strong dose-response relationship between industrial toxins and diabetes. Since then, Harvard researchers have reported a link between persistent pollutants like hexachlorobenzene and diabetes in their Nurse’s Health Study (See Food Sources of Perfluerochemicals). This is supported by an analysis they did of six other studies published since 2006 that showed the same thing. The Harvard researchers conclude that “past accumulation and continued exposure to these persistent pollutants may be a potent risk factor for developing diabetes.”

Where is hexachlorobenzene found? In a U.S. supermarket survey, salmon and sardines were most heavily tainted with hexachlorobenzene, with salmon “the most contaminated food of all.” Farmed salmon specifically is perhaps the greatest source of dietary pollutants, averaging nearly ten times the PCB load of wild-caught salmon.

Wait, isn’t there a flaw in this argument? Since many of these chemicals were banned in the 70’s, the levels inside people have been going down, whereas the rates of diabetes have been shooting straight up. Therefore, how could pollutant exposure be causing diabetes? This puzzle may be explained by our epidemic of obesity. The nationwide study found that the association between these toxins and diabetes was much stronger among obese subjects than among lean subjects. As people get fatter, the retention and toxicity of pollutants related to the risk of diabetes may increase.

So we’re not just exposed by eating the fat of other animals; our own fat can be a continuous source of internal exposure because these persistent pollutants are slowly but continuously released from our fat stores into our circulation.

They don’t call them “persistent pollutants” for nothing. These chemicals have such a long half-life that people consuming regular (even just monthly) meals of farmed salmon might end up retaining these chemicals in their bodies for 50 to 75 years.

Hexachlorobenzene in fish has been tied to diabetes; what about the mercury? A 1995 study highlighted in my video, Pollutants in Salmon and Our Own Fat, out of Japan found that diabetics do seem to have higher mercury levels in their body. Mercury alone does not seem to increase diabetes risk, though. It may be the simultaneous exposure to both dioxins and mercury that increases risk, so the safety limits for dioxins and mercury individually may underestimate the risk when they’re consumed together in seafood.

So while the pharmaceutical industry works on coming up with drugs to help mediate the impact of these pollutants, a better strategy might be to not get so polluted in the first place.

Unfortunately, because we’ve so contaminated our world, we can’t escape exposure completely. You have to eat something. Some foods are more contaminated than others, though. Exposure to these pollutants comes primarily from the consumption of animal fat, with the highest levels found in fatty fish like salmon. Farmed Atlantic salmon may be the single largest source of these pollutants, and that’s the kind of salmon we most commonly find in supermarkets and restaurants.

We hear about advisories warning pregnant women to avoid the consumption of food containing elevated levels of pollutants and mercury, but as a public health journal article points out, since these toxins bio-accumulate in the body for many years “restricting the exposure to these pollutants only during pregnancy would not protect the fetus or future generations against the harmful effects of these hazardous chemicals.”

For the existing links between seafood and diabetes risk, see Fish and Diabetes and I explored this concept of our own body fat as a reservoir for disease-causing pollutants in Diabetes and Dioxins.

More on hexachlorobenzene in my video Food Sources of Perfluorochemicals.

Our body has a tougher time getting rid of some toxins than others:

The best way to detox is to stop toxing in the first place.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

64 responses to “Salmon May Be the Greatest Source of Dietary Pollutants

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  1. Not arguing for eating salmon. But you need to ditinguish between wild caught Alaskian salmon and farm raised, the latter being much more contaminated than the former

        1. Here’s a quote from the article: “Farmed salmon specifically is perhaps the greatest source of dietary pollutants, averaging nearly ten times the PCB load of wild-caught salmon.”

          What do you feel is missing?

          1. well thanks Thea! I really don’t get people in comments sections… Somehow I usually refrain from commenting because of that. So, thanks for the quoting :)

          2. Thea, do you personally eat seaweed, and do you think it holds ocean pollution risks
            that some of the seafood does? Logical as possibility, huh?

            1. guest: Yes, I personally eat seaweed. I’m a fan of nori. And just this last weekend, I threw of handful of arame (sp?) into my cooking beans. When I drained the water, I didn’t try to pick out the arame. I just ate the seaweed with the beans. Yummy!

              pollution risks: Any food grown anywhere is going to be contaminated to one degree or another because we have polluted our world just that badly. It’s not just the ocean we have to worry about. The question is, do we need to worry more about plants grown in the ocean than those grown on the land? I think there is a whole lot of ‘it depends’ in the answer. There’s no simple rule of thumb would be my guess.

              My eating philosophy is to stick to the lowest contaminated foods as much as possible while also keeping in mind that food is a package deal. (Meaning that all of the bad stuff, including contaminants, have to be weighted against all the good stuff to decide whether or not to eat a food.)

              There is a well known, well accepted, uncontroversial phenomenon where the higher up the food chain you go, the more contamination you get.

              So, putting all that together: Yes, our oceans are polluted, but I expect that eating seaweed would *generally* (I understand that there are exceptions) be the least polluted way to eat seafood as it is the lowest place you can get on the food chain. And *generally* plant foods from the oceans seem to have more value on the plus side than the negative. That’s my opinion, not based on a particular scientific paper.

              That’s my take right now anyway. I think this is an evolving story as we continue to pollute and kill our oceans more and more. So, I could see my answer changing in the future due to changing conditions or simply more education on my part.

              Whew. You ask a simple question and get an essay answer. What’s up with that?

          3. The title says “salmon” not farmed raised salmon creating an impression that it applies to all salmon for one who either reads the title but not the article or doesn’t read the article carefully.

    1. It’s worth noting that many of the salmon caught and labeled “wild” was actually raised in the hatcheries for up to one year, then released. Also, alot of farmed salmon is mislabeld and sold as wild, so it’s hard to know what you’re eating. So I think the title is not misleading. But also, it’s not feasible to put every detail in the title, that’s what the article is for.

    1. It is in the food. They are fed other fish usually ground up as pellets. Dr. Richard Oppenlander’s book, Food Choice and Sustainability, has a chapter entitled, Our Oceans and Aquaculture, which is very enlightening. The environmental impact of “concentrated raising of fish” aka farmed fish is very under reported and under appreciated in my experience.

    2. This is what I think: Farmed salmon is raised closed to the shore in populous areas, whereas wild salmon comes from the deep waters in isolated places like Alaska.

      1. It isn’t always the location, but rather where on the food chain the fish are feeding. Pennsylvania had to put a consumption advisory on fingerling (Rainbow Trout, I think) that it raised in hatcheries to stock in Lake Erie. Once in the lake, the advisories were eventually lifted as the fish grew consuming a variety of wild invertebrate and other foods. (In hatchery, the state fish, like most Rainbow Trout sold in stores, were fed fish meal from deep isolated ocean waters.)

        Likewise, wild Sockeye Salmon feed on invertebrates among other things–like flamingos, that’s where they get their pink color. Farmed Atlantic Salmon are fed fish meal and their white flesh must be dyed to meet expectations of the consumer. So, not only do farmed salmon tend to be more contaminated (fed fish meal), they are dyed, and some, like those farmed in Chile, can only be raised with high doses of antibiotics. (Raised in net pens, it’s difficult to avoid disease as one might in a land-based facility by UV-ing incoming water, etc., and Chile’s netpens have especially big disease problems. Salmon from farms in Norway are reported to use ~1/10th the antibiotics.)

        1. Incredibly incorrect and misinformed. Farmed salmon feed includes Astaxanthin which is the carotenoid found in krill and gives the salmon flesh the orange color. You can buy Astaxanthin over the counter as a health supplement. It’s also an essential nutrient for the health of the salmon. Dyes are not, and have never been, used in farming salmon. The simple truth is the world would be a much healthier place if we all consumed more seafood – whether farmed or wild.

  2. A little off-topic here but I wanted to share an experience related to skin cancer risk. I am a pale-faced redhead and I live in Arizona where most days are quite sunny. Today I had my annual dermatology visit to check for precancerous lesions. In past years the doctor has had to burn off a handful of such lesions from my face. Today I got a clean bill of skin health–no lesions at all. I’ve been doing WFPB for about three years and I usually (but not always) put sunscreen on my face when I go out. I like to think my lifestyle is helping me out here.

    1. Hi Kay. Thanks for sharing the good news! A wholesome diet is important for skin health so there may be a connection. Let’s hope next year is just as good! Please don’t hesitate to ask more questions (off topic ones are fine) if any come to mind.


      1. You’re so right about skin health. I work in a wound clinic now and unfortunately see many cases that I would consider to be lifestyle related–diabetic foot ulcers, leg ulcers, poorly healing surgical wounds, maybe even some of the autoimmune issues. The only dietary recommendation the doctors and NPs give is to “eat more protein” because it promotes healing. I always tell them to eat legumes and vegetables. People are so surprised to learn that protein doesn’t have to come from an animal source.

    2. Great news Kay. I had some stuff growing out of my face and it went away when topically applied turmeric paste in oil. Also wash daily with turmeric soap. FWIW…good luck.

      1. Rhombopterix: I have to ask, “turmeric soap”? I can’t get anywhere near turmeric without staining everything yellow. How does it work for you? Do you make it yourself, or is it a product you buy? Just curious.

        1. I’m so proud of my soap. We started making it on a lark and it is so much nicer than the chemical goop sold, we just could not go back. After I learned about turmeric’s anti-tumor properties and my success with it I was determined to try this out. If you are interested I am more than happy to send a block to you. It really works.

          FYI, soap has an alkaline pH that tones down the blazing yellow to a pleasant brown yellow. An the hydrophobic character of curcumin allows it to easily integrate into a homemade soap.

          I have seen a fantastic improvement to my own skin since making this small change.

          1. Rhombopterix: That’s really cool! I use liquid soap rather than bar soap. So, I’ll pass on your very generous offer. I love how you made your own. Maybe some day in the future you will go into business with the stuff and make it big!!

            1. I suggest that you try a ratio of 1 part turmeric to 9 parts liquid soap and see what happens. Although after looking into the composition of commercial “soap” I would think twice about using at all.

              In my case the only part that turned yellow was the tumor itself…there is no staining of the skin (as I also had feared). Actually one of my other personalities posted the photo record here some years ago. There are several “people” living inside my head but I am the only one you should listen to : ) Turmeric reduced the growth to a pin-head in 3 days and was completely gone after a course of 2 months daily application. I really don’t know if it was cancer or what..but it was a new and rapidly growing, weaping thing.

              1. Rhombopterix: That’s really fascinating stuff. And I appreciate the 1 to 9 parts info. It is a very intriguing idea.

                re: thinking twice
                Well, I do use a brand called Castile, that I think it supposed to relatively safe. I know I’m not up to creating my own soap at the moment. But it’s something to think about. I do like the idea of it.

                Thanks again.

                1. Actual Castile soap is made with olive oil. If that is way you have it is good. I just meant that if you have skin problems and want to try turmeric I would recommend that mix. Best wishes Thea

    3. Kay, I had the same experience with facial skin lesions after going predominately vegan in 2011. This may be an indication of what is going on internally as well.

  3. Canadian scientists have found that the cleanest wild salmon are the pinks. They live a relatively short time and feed low on the food chain. Chum are also quite clean, they say, but contain few omega 3s. Sockeye also feed fairly low on the food chain and migrate farthest out to sea, but live a bit longer than pinks, thus accumulating more pollutants. Chinook and coho feed highest, and some kinds feed close to shore, where there’s more pollution. Bottom line: If you’re going to splurge, choose pink or sockeye.

    Sources here: http://eatandbeatcancer.com/2012/06/06/salmon-says-an-anti-cancer-investigation-what-kind-is-healthiest-summary/

  4. What surprises me are the sardines, which were the last fish I gave up eating on a regular basis, because of their supposed high nutritional benefits with minimal toxins (see http://www.whfoods.com/genpage.php?tname=foodspice&dbid=147). Unlike salmon, they’re plankton feeders (lowest on the food chain) and caught when still relatively tiny—so how to they manage to bioaccumulate so much hexachlorobenzene in their short, vegetarian lifetimes? More than even tuna, shark, swordfish, bluefish, and other carnivorous species? Something fishy here….

        1. Thanks, Rami. It’s interesting that the canned tuna they tested in that study were so much cleaner than the salmon and sardines. Any thoughts? Is canned tuna fatty?

          My hunch on sardines–and it’s only a hunch, but let’s have a discussion–is that Europe’s waters, where many sardines come from, are filthy due to its long history of industrialization. More on that here http://eatandbeatcancer.com/2012/04/13/salmon-says-an-anti-cancer-investigation-part-4-how-healthy-is-farmed-atlantic-organic/

          And now, for the first time, we’re starting to see Fukushima’s footprint off our Alaskan shores.http://fukushimainform.ca/category/blog-2/

          1. Actually European waters here in the south, where sardines come from mostly, is really clean.
            The north is where heavy industries exist.

              1. Portuguese Atlantic waters, the biggest oceaninc economic region in the world.
                You’ve got sardines in the north of Spain (Atlantic) and Morocco too.

  5. What about rice, as bacteria in rice fields convert inorganic mercury into organic mercury absorbed by rice plants? I have been avoiding brown rice sweetener and making my own almond milk with natural vanilla only. I am also worried about downstream runoff and wind drift of toxic pesticides, herbicides etc. to organic farms. What is not contaminated now?

  6. In regards to farmed vs wild, the article says wild has, on average, 10x less of the pollutant than farmed, how does that put wild into perspective though?

    Is it 10x less but still much higher than we should be eating? Or is the 10x less enough of a reduction that occasional consumption is ok, especially considering the relative healthiness of fish compared to other animal protein (afaik).

    Been trying to cut down on animal protein but sometimes I need SOMETHING and wild sockeye salmon has been my go-to for the last few weeks..

    1. S Slavin: I haven’t checked myself, but the source cited in the following video may answer your question:

      I was focusing in the part: “Like getting thyroid disruption from the flame-retardant chemicals, which literally just settle out of the atmosphere such that even fish who only swim in Antarctica are contaminated.”

      But I understand I didn’t answer your actual question. I just hope I’m giving you another avenue of research. I understand that the psychological aspects of giving up meat can be hard. It might be worth it to get over that hump though…

      Good luck.

      1. Thanks – there is indeed some useful information in there as well the comments, will look through it in more detail.

        I feel like we’ve polluted the planet so badly that there is no hope for fish…maybe I should just get some pet salmon although I’ll probably not want to eat them after bonding :-).

  7. I read from the Environmental Working Group that researches all things for toxins etc. that wild salmon, rainbow trout and Atlantic Mackerel were the safest fish as far as mercury and also had very high omega-3’s. I am a vegan for the most part but like to fall off the wagon every now and then and have fish. Has anyone done more research as to the safest fish to eat considering the toxins and mercury? I know the smaller the better I’ve read as the big fish eat little fish etc.

  8. Let’s face it the oceans today are polluted swamps.
    After all the cr@p we humans have been steadily pouring into them for nearly a century how could they not be!
    Now it all comes back to bite us through the food chain.
    These days, if it crawls, flies or swims I won’t eat it. Period.
    Only what grows out of the ground.
    In other words WFPBD. I ultimately have to thank Dr. Greger and this site for my enlightenment.

  9. I have mentioned this before , but this is very interesting because I used to get a splitting headache for about 1 ~ 2 days every time after consuming salmon. I did not miss the migraines after going WFPB vegan.
    The wild, smaller variety was fine.

  10. I would like you, Dr Greger to discuss this issue publicly with Dr Kruse. He says that it is better to consume full of toxins but at the cost of getting substantial amounts of DHA than not to consume sea cold water fish at all. Dr Greger, you continuue constantly to pick holes in non-vegetarian food. Please sum up some courage to find holes in mono-vegetarian foods. Such serious researchers like you should first and foremost expose something negative concerning the food you are blindly defending. Only then can you talk about the advantages of vegetarian diet. Please, don’t get me wrong, I am NOT against consuming veggies. I love them and consume them in industrial quantities but food is not only fruits and veggies. A human being has always eaten meat and will continue to do so in spite of warnings of the researchers like you, Dr Greger. And it does not mean that more than the half of the population of the Earth is stupid because they are meat-eaters. Yes, it is true that we overconsume meat and we have caused imbalance in our diet and therefore we should consume less but it does not mean that we must stop eating meat altogether.

    1. How is summarizing the latest scientific research “blindly defending”. You have a very interesting definition of “blindly defending”. And if you don’t think Dr. Greger doesn’t find negative aspects as well as positive aspects of foods, then you can’t have viewed very many of the thousands of videos on this website. Dr. Greger regularly reports on the pluses and minuses of many common whole plant foods and has no compunction against saying that a given food has more negatives than positives.

      I did a little research on Dr. Kruse and he is a neurosurgeon. I am sure that he is eminently qualified to do brain surgery, but the simple fact that he has completed medical school and training doesn’t mean that he has any training in nutrition. Fewer than a quarter of medical school require students to take any classes in nutrition, and of those that do it is just a few hours of class time usually embedded in other classes. Now that doesn’t say that Dr. Kruse didn’t pursue education in human nutrition outside of his medical education, but his being a doctor does not by itself qualify him to speak authoritatively on the subject of human nutrition. So maybe he has done this outside education, but I see from his website on “achieving optimal health” that he advocates a Paleo diet, which does not fill me with confidence that his viewpoints are well rooted in science or logic. The entire Paleo hypothesis rest on arguments that are riddled with bad science and flaws in logic. For a complete, some might say excruciating, review of the flaws in the Paleo argument I recommend the Primitive Nutrition series of videos at plantpositive.com. So please sum up some courage to find holes in your mono-meat foods and view these videos rather than blindly defending the views of Dr. Kruse.

      1. By stating that I am a mono-meat eater you are showing that you don’t understand a simple text in English. If you have difficulties I can write the same in 4 different languages. Perhaps it will be easier for you.

        I have never heard anything positive in Dr Greger’s videos or articles concerning non-vegetarian diet.

        Besides I am not defending Dr Kruse, let alone blindly. Why are you explaining to me that Dr Kruse did not study Nutrition at a medical school. Does anyone have to take an official course in Nutrition to know a thing or two or even more about nutrition?

        You have given away your prejudice against the Paleo diet – so what shall we discuss if you see nothing but veggies as food? Everything is flawed with all ideas concerning food save for a vegetarian approach or even vegan. You did not even have willingness to see some extraordinary ideas coming from Dr Kruse, because you disqualify him from the very beginning – you must have a very closed mind. Paleo acts on you like a red rug acts on a bull.

        You are picking on some lack of scientific logic among your opponents, but tell me – has a human being always consumed meat?Or is it only a recent craze? And the rest of the discussion is the waste of time. Open up your eyes – stop wearing your blinkers. If Dr Kruse is difficult (I mean his ideas) read Dr Hyman or Dr Perlmutter or dip into the ideas of Dr Osborn and last but not least Dr Kresser – read especially his article you will adore… http://chriskresser.com/why-you-should-think-twice-about-vegetarian-and-vegan-diets/

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