Fish, measuring the good and the bad

Seafood is a source of long-chained omega-3 fats that our bodies need. Seafood is also a good source of iodine and vitamin D. Yet despite these important nutrients, we are advised to limit how much fish we eat. Most of the advice we get on whether and how to limit our seafood choices is simply based on mercury measurements. The FDA and EPA recommendations that we eat 6-12 ounces of seafood each week while avoiding four species of fish (shark, swordfish, tile fish, and king mackerel) especially if we are pregnant or nursing or feeding children is based on mercury evaluations. Similar considerations lead to the recommendation that we limit albacore tuna, chunk white tuna, and tuna steak to 6 ounces a week while being advised to instead eat shrimp, crab, canned light tuna, salmon, pollock, catfish, cod, and tilapia.

A recent French study did a more in depth analysis of the risk-benefits of seafood and came up with some interesting and slightly different recommendations. In this study, they balanced seafood benefits (omega-3s, iodine, vitamin D) against its detriments. Those detriments included mercury but went further acknowledging that our seafood also is a source of inorganic arsenic, and a wide variety of persistent pollutants including dioxins, polychlorinated biphenyls, and polybrominated diphenyl ethers (PBDE, flame retardants) to name a few. Thus, while eating seafood nutrients helps prevent heart disease, strokes, cancers, depression, and certain neurodegenerative diseases, its toxins are neurotoxic and place a substantial burden on the liver, kidney, and thyroid.

The French study evaluated seafood based on the beneficial components of the seafood. For instance, a fatty fish like herring is much richer in omega-3s and vitamin D than lean fish (such as sole), mollusks (such as squid), and crustaceans (such as lobster). Thus, herring got a higher “beneficial” rating than lobster. However, fat content is not the end-all-be-all given that two fish with the same fat content can have very different amounts of omega 3 fats. For instance, mackerel may have some 20 times as many omega-3s as an “equally fatty” cat shark.

The toxin content also factored into the creation of the seafood hierarchy because, depending on the size, habitat, longevity, and so on, different species of seafood contain different amounts of toxins.  This was a French study so naturally it looked mostly at seafood species eaten in France, and those are mostly Atlantic species. They looked at the data on these fish and then created a formula that balanced the benefits against the detriments. Thus, a fish with a goodly amount of vitamin D with some arsenic, PCBs, etc. might score better than another fish less rich in D but also less rich in arsenic and dioxins.

The results were interesting, if slightly depressing if you love seafood: Five clusters were created, three of which contained seafood where the detriments outweighed the benefits.  Fresh crab and sea bass are in this group. The good news is that the species of fish most favor belong in the “to eat” cluster: Salmon, canned sardine and mackerel, halibut, swordfish, and smoked salmon. Bad news: We should limit ourselves to 6 or 7 ounces of these foods a week. That means two small servings a week. The last cluster also included many species we like to eat: Shrimp, sole, canned tuna, oysters, mussels, lobster, and canned crab. Bad news: Only 1 or at most 2 ounces a week. That is not much at all. So eating 7 ounces of fish from the first group and 1 ounce of seafood from the second group will ensure that we get a maximum amount of vitamin D with a minimum of arsenic while meeting our needs for omega 3s but without exceeding the guide lines for cadmium, dioxins and PCB.

Of course, I immediately began wondering what the equivalent evaluations of other animal products are. What is the optimal amount of beef, dairy, lamb, and chicken to be eaten each week? Has anyone compared the toxins in a truly pastured chicken with a factory-farmed layer? I have yet to find those studies but I am looking. And, of course, I want to know whether eating more than 7 ounces of fish while eating less land animals is better than frequently eating chicken and cheese while carefully limiting crab. I am not sure there are studies that have looked closely at these questions. I would expect the nutritional benefit of beef to easily be outweighed by its toxin content. I would expect that to hold true for all factory-farmed food whether eggs, chicken, turkey, lamb, or cheese but some data would be nice.

Ultimately it does seem that, given the environmental toxins we now are awash in, we need to become more selective about which animal products we eat, choosing those that provide the most nutrients and consciously avoiding those most heavily laden with persistent toxins.

Photo: “Pez espada”  by FreeCat (Jose Antonio Gil Martinez)

NOTE: You are welcome to use my blog’s original images and content for non-commercial purposes if you attribute the work to me (Kathy Abascal) and link back to the blog. This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 United States License.


About kathyabascal

Herbalist with a background in neurobiology, biochemistry, and law. Teacher of the TQIDiet, how to quiet inflammation with food.
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16 Responses to Fish, measuring the good and the bad

  1. Nan Wilson says:

    Thanks for the update Kathy. And nudge to watch toxins.

  2. Ceu says:

    Good wake up call. More and more I don’t even want to eat anything, or I eat very little of any mentioned in post, and eat lots of vegetalbe based foods, beans, there are so many varieties in the different cultural communities. Love your work Kathy.

  3. kathyabascal says:

    We could all use that positive approach to foods a bit lower on the food chain; many ethnic cuisines use fish and meat more as condiments than as the centerpiece of a meal.

  4. Shawn says:

    So, based on this, and given that beans are higher in Omega 6’s if I understand that correctly, are we better off to eat a small portion of acceptable fish and then use organic, Omega 3 eggs and nuts to get our high quality protein? This is always the point that confuses me as it seems we need to watch our beans given the omega 6 issue. And thanks for updating us! :0)

    • kathyabascal says:

      The best way to avoid environmental toxins, is to include more plant proteins in our diet. We do not need to avoid beans to maintain a balance of essential fats; remember, it is the ratio that is important. So when you eat beans include green vegetables, flax seed, walnut or pumpkin seed oil to increase the 3s in your diet. Ultimately it is balance that matters.

  5. Elise says:

    I just found this site, it looks wonderful and I’m so excited to learn more! Here is a good video regarding fish:

    • kathyabascal says:

      That was an interesting video. Of course, its only short coming is that it focuses only on mercury. The French study went a bit further looking at other toxins (flame retardants, PCBs, dioxins, etc.) so their recommendations were a bit different. Fascinating about the different mercury standards set by the FDA and EPA though and some good references. Thank you for sharing!

  6. Brooke says:

    What about young pastured ruminants like lamb, grown well away from industry, fracking, or highways? I know prevailing winds can carry all sorts of badness anywhere on the planet, but I suspect where I get mine from, the Umpqua Valley in Oregon might be about as safe as it gets for animal protein and fat (fingers crossed that not much from Fukoshima has landed on those fields), and the fatty acid profile is darn good.

    • kathyabascal says:

      Saturated fats have the ability to interfere with our ability to use essential fats well. Our hunter gatherer ancestors ate much leaner animals than we do so while pastured lamb is a perfectly ok food, I would not treat it as a source of omega 3s. Moreover, we are talking about environmental toxins here: Fish can be far away from industry, fracking, and highways and be quite high in toxins. So is lamb.

      • Brooke says:

        I failed to mention that my focus on lamb, as opposed to say grassfed beef here, is that the meat is culled young, and therefore wouldn’t have had time to accumulate as many toxins (beyond a small amount of the persistent ones that can cross the placenta like some pesticides and plastic residues, but clean grazing should help), kind of like the benefit of eating lower food chain fish. We both live in the shadow of the Tacoma smelter plume, so gardening food crops in native soil, and backyard ranching might not be the best idea around here without some serious soil modification, but I do believe there are pockets of a realitively clean land out there still, with undisturbed water tables that can provide us with safe animal foods.

        I suspect avoidance can only get us so far, I have faith that people like Paul Stamets who is developing systems with mushroom that can transform unusable contaminated land into acres of edible oyster mushrooms, and Nathalie Jeremijenko with her environmental health clinics and “no park” project are paving the way to turn the ship around.

      • kathyabascal says:

        A young lamb may have fewer toxins than the ewe but much like human infants will have been accumulating these toxins from the moment of conception. . .


        My blog:http://www.TQIDiet.wordpress.comLatest post: Feel Free to Enjoy Your Cup of Coffee.

  7. Brooke says:

    Sorry to beleaguer the point here Kathy, but I had never heard about saturated fat messing with efa metabolism before and did a little looking around to see what I could find. The studies I found used hydrogenated coconut oil, and that of course would be a bad idea for anyone to eat for a whole host of reasons. Dr. Mary Enig had an interesting post on the Weston A. Price site from a copy of their journal in 2005 (maybe more research on this has come out since then that you have seen and I haven’t come across yet), but this is what it said,
    “Finally, it should be stressed that certain components of the diet actually reduce (but do not eliminate) our requirements for EFAs. The main one is saturated fatty acids which help us conserve EFAs and put them in the tissues where they belong. Some studies indicate that vitamin B6 can ameliorate the problems caused by EFA deficiency, possibly by helping us use them more efficiently.”

  8. Mary says:

    Hi Kathy. Since I eat more salmon than the study’s recommended 6 or 7 oz a week, I will be very interested in whatever else you can uncover about the relative benefits and risks of eating more fish than that compared to eating land animals. I don’t eat any land animals and don’t wish to, though I have eggs and very occasional dairy.

    • kathyabascal says:

      Fish provid omega 3s, vitamin D, and iodine; I do not know what the equivalent benefits of land animals products, including dairy and eggs, might be. You certainly can find studies on the environmental toxin accumulation in land animals, so the same detriment present in fish is present in them. I assume that means that eating more fish than dairy would be beneficial.

      • Mary says:

        Thanks, Kathy. Dairy has gone through two levels of bioaccumulation, from grass to cow to milk, so it may be even more contaminated. One concern is that the fallout from nuclear tests concentrated especially into the grasses that cows eat. I can’t think of anything special that land animal products provide that fish doesn’t– some have a little DHA but fish has more.

  9. Brooke says:

    I was recently reading about the protective benefits of selenium that already exists in salmon and binds to the mercury, creating an inert substance that isn’t dangerous to humans the way free mercury is when it is in grains. I know that doesn’t cover all of what we can expect to find in something we pull out of the ocean, but it does make me wonder if we need to worry as much about mercury, at least in salmon?

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