Fish & Diabetes

Fish & Diabetes
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The relationship between fish consumption and diabetes risk may be due to toxic pollutants that build up in the aquatic food chain.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In the past two years, six separate meta-analyses have been published on the relationship between fish consumption and type 2 diabetes. The whole point of a meta-analysis, though, is to compile together the best studies done to date, and see what the overall balance of evidence shows. The fact that there are six different ones published recently highlights how open the question remains. One thread of consistency, though, was that fish consumers in the United States tended to be at greater risk for diabetes.

If you include Europe too, then fish-eaters appeared to have a 38% increased risk of diabetes. On a per-serving basis, that comes out to be about a 5% increase in risk for every serving of fish one has per week. To put that into perspective, a serving of red meat is associated with a 19% increase in risk—but, that’s per day. Just one serving a week of fish is 5%, so a serving a day would be like a 35% increase in risk—worse than red meat, but why?

Well, fish intake and omega-3 fats may increase type 2 diabetes risk by increasing blood sugar levels, as found in a review of the evidence commissioned by the U.S. government. An increase in blood sugars in diabetics given fish oil. Or, it may be because the omega-3s cause “oxidative stress.” A recent study found that the insulin-producing cells in the pancreas don’t appear to work as well in people who eat two or more servings of fish a week. Or, it may be because of the “environmental contaminants” that build up in fish.

It all started with Agent Orange. We sprayed twenty million gallons of the stuff on Vietnam, and some of it was contaminated with trace amounts of dioxins. Though the Red Cross there estimates a million Vietnamese were adversely affected, what about all the servicemen, the U.S. servicemen, who were exposed, spraying it across the countryside? Reports started showing up that veterans exposed to Agent Orange appeared to have higher diabetes rates than unexposed veterans—a link that’s now officially recognized.

These so-called “persistent organic pollutants…are mainly man-made [industrial] chemicals…, and…among the most hazardous compounds ever synthesized. [They] include…dioxins,…PCBs, and certain…chlorine-containing pesticides, [all of] which are highly resistant to [breaking down in the environment].”

“Initially described for their deleterious effect[s] on reproductive function” and their ability to cause cancer, “there is now [a] growing body of evidence showing that exposure to [these pollutants] leads to metabolic diseases,” such as diabetes. This is “a breakthrough that should require our greatest attention.”

Please consider volunteering to help out on the site.

Images thanks to falco via Pixabay, Brian K. Grigsby via Wikimedia, and James Nachtwey via flickr

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In the past two years, six separate meta-analyses have been published on the relationship between fish consumption and type 2 diabetes. The whole point of a meta-analysis, though, is to compile together the best studies done to date, and see what the overall balance of evidence shows. The fact that there are six different ones published recently highlights how open the question remains. One thread of consistency, though, was that fish consumers in the United States tended to be at greater risk for diabetes.

If you include Europe too, then fish-eaters appeared to have a 38% increased risk of diabetes. On a per-serving basis, that comes out to be about a 5% increase in risk for every serving of fish one has per week. To put that into perspective, a serving of red meat is associated with a 19% increase in risk—but, that’s per day. Just one serving a week of fish is 5%, so a serving a day would be like a 35% increase in risk—worse than red meat, but why?

Well, fish intake and omega-3 fats may increase type 2 diabetes risk by increasing blood sugar levels, as found in a review of the evidence commissioned by the U.S. government. An increase in blood sugars in diabetics given fish oil. Or, it may be because the omega-3s cause “oxidative stress.” A recent study found that the insulin-producing cells in the pancreas don’t appear to work as well in people who eat two or more servings of fish a week. Or, it may be because of the “environmental contaminants” that build up in fish.

It all started with Agent Orange. We sprayed twenty million gallons of the stuff on Vietnam, and some of it was contaminated with trace amounts of dioxins. Though the Red Cross there estimates a million Vietnamese were adversely affected, what about all the servicemen, the U.S. servicemen, who were exposed, spraying it across the countryside? Reports started showing up that veterans exposed to Agent Orange appeared to have higher diabetes rates than unexposed veterans—a link that’s now officially recognized.

These so-called “persistent organic pollutants…are mainly man-made [industrial] chemicals…, and…among the most hazardous compounds ever synthesized. [They] include…dioxins,…PCBs, and certain…chlorine-containing pesticides, [all of] which are highly resistant to [breaking down in the environment].”

“Initially described for their deleterious effect[s] on reproductive function” and their ability to cause cancer, “there is now [a] growing body of evidence showing that exposure to [these pollutants] leads to metabolic diseases,” such as diabetes. This is “a breakthrough that should require our greatest attention.”

Please consider volunteering to help out on the site.

Images thanks to falco via Pixabay, Brian K. Grigsby via Wikimedia, and James Nachtwey via flickr

Doctor's Note

This is the first of a three-part video series on the role industrial pollutants may play in our diabetes epidemic. Stay tuned for Diabetes & Dioxins and Pollutants in Salmon & Our Own Fat.

For more on the changing views surrounding fish oil supplements, see Is Fish Oil Just Snake Oil?

Other foods associated with diabetes risk include processed meat and eggs; see Bacon, Eggs, & Gestational Diabetes During Pregnancy and Eggs & Diabetes—while Indian gooseberries and flax seeds may help (see Amla vs. Diabetes and Flax Seeds vs. Diabetes).

Other videos that touch on how polluted our oceans now are include:

If you haven’t yet, you can subscribe to my videos for free by clicking here.

47 responses to “Fish & Diabetes

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  1. Thank you Dr. Greger and staff. I’ve been eating a WFPB diet for almost 3 years now and your work helps me to make prudent choices.




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  2. I would like to echo my appreciation. The main reason I do not consume fish is for ethical reasons; our civilization has declared a full-scale war on fish species in the oceans.

    My understanding though from the literature is that consumption of oily fish and in particular the omega-3 PUFA present in oily fish (salmon, tuna, etc) actually lowers the risk of atherosclerotic coronary artery disease. This would be contrary to the effects on diabetes incidence. How does one reconcile these differences?

    I suppose the DART and DART-2 trials, particularly their long-term follow-up reports, did definitively show no benefit of recommending avid fish consumption for preventing heart attacks or death.

    http://www.ncbi.nlm.nih.gov/pubmed/17343767

    http://www.ncbi.nlm.nih.gov/pubmed/12032650




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    1. magicoyote: I’m not a definitive source for this question, but it is my understanding that algea-derived DHA and EPA pills (as of now) come from algea grown in a controlled tank in a factory – not gathered from wild sources. So, to my thinking, assuming they started off with pure materials, contamination risk would be almost non-existent.




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      1. wow, I had no idea! but that makes sense, thanks! and thanks for your amazing work. This is the best website on the internet for real information I can trust!




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  3. I wonder, are you beginning to question the recommendation to supplement the vegan diet with omega 3’s derived from algae? This is something that has long been marketed and recommended by Dr. Fuhrman. If I take this oil at the recommended dose I get some rather impressively colored bruises. I have the notion that my blood should stay in my veins, so I have stopped this practice.




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    1. Just a vegan…
      the recomended ratio omega 3/6/9 is 1/4/1. As vegans we dont get to much omega 6. If you add too much omega 3, which act as a blood thiner, you’ll get those colorful bruises.




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  4. ” A recent study found that the insulin producing cells in the pancreas
    don’t appear to work as well in people who eat two or more servings of
    fish a week.”

    What’s that they say about change being the only thing permanent? It was only a matter of time before the “eat two or more servings of fish a week” advice got skewered too. Other foods have had their turn. But then, fish did receive a lot more than a mere 15 minutes worth of fame.




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    1. Questions of contamination aside, do algae based DHA/EPA supplements affect the B cells (insulin producing cells) in the pancreas?




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      1. To my knowledge, there aren’t any studies on algal DHA/EPA and insulin resistance, metabolic syndrome, diabetes, or pancreatic β-cell function function. In general, there appears to be an inverse association of dietary and plasma n-3 fatty acids with metabolic syndrome in humans, which most authors attribute to inhibition of inflammation (a pathway for muscular insulin resistance and β-cell death).

        This cohort study tried to disentangle the ω3’s from the contaminants in inflammation markers, and supports Dr. Greger’s theory. Similarly this study found crude salmon oil caused metabolic syndrome in rats, but refined salmon oil (with the contaminants removed) did not. One older study that found marine oil impaired pancreatic insulin production, but its not at all clear whether the fish oil was refined to remove POPs.




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        1. Jeff Novick recently shared an article discrediting current recommendations for fatty fish, especially after being modeled from the Inuits.

          “Eskimos do have a similar prevalence of CAD [coronary artery disease] to non-Eskimo populations, and in fact, they have very high rates of mortality due to cerebrovascular events (strokes). Overall, their life expectancy is approximately 10 years less than the typical Danish population and their overall mortality is twice as high as that of non-Eskimo populations.

          “Considering the dismal health status of Eskimos, it is remarkable that instead of labeling their diet as dangerous to health, a hypothesis has been construed that dietary intake of marine fats prevents CAD and reduces atherosclerotic burden,”
          http://www.sciencedirect.com/science/article/pii/S0828282X14002372
          http://www.elsevier.com/about/press-releases/research-and-journals/investigators-find-something-fishy-with-the-classical-evidence-for-dietary-fish-recommendations

          I post this to add to your n-3 comment.




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  5. I would change the last sentence in the last article you quoted from, “SHOULD require our greatest attention.” to, “DEMANDS our greatest attention!”
    Well put together!




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      1. It is interesting that “reductionistic” thinking and research is coming up with alot of ideas for the cause of type 2 diabetes… in this case omega 3 & dioxin. The science clearly supports that high fat consumption is associated with diabetes and obesity. You can view other video’s on this site relating to diabetes. I think especially relevant is http://nutritionfacts.org/video/how-to-treat-diabetes/ which highlights the work of Dr. Neal Barnard’s research (he is the founder and leader of PCRM) which demonstrates a low fat diet is the best treatment for type two diabetes… vegans need to avoid oils and minimize nuts at least until they are off medications and their fasting sugars have returned to normal range. Since fish is so high in fat it should be avoided regardless of cooking methods and it is not a surprise that fish consumption is related to type two diabetes.




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          1. The okinawan population of Japan did not eat alot of fish, their diet was mostly sweet potato. As Jeff Novick has shared:

            Caloric Restriction, the Traditional

            Okinawan Diet, and Healthy Aging

            The Diet of the World’s Longest-Lived People and Its Potential Impact on Morbidity and Life Span

            Ann. N.Y. Acad. Sci. 1114: 434–455 (2007).

            TABLE 1. Traditional dietary intake of Okinawans and other Japanese circa 1950

            Total calories 1785

            Total weight (grams) 1262

            Caloric density (calories/gram) 1.4

            Total protein in grams (% total calories) 39 (9)

            Total carbohydrate in grams (% total calories) 382 (85)

            Total fat in grams (% total calories) 12 (6)

            Saturated fatty acid 3.7

            Monounsaturated fatty acid 3.6

            Polyunsaturated fatty acid 4.8

            Total fiber (grams) 23

            Food group Weight in grams (% total calories)

            Grains

            Rice 154 (12)

            Wheat, barley, and other grains 38 (7)

            Nuts, seeds Less than 1 (less than 1)

            Sugars 3 (less than 1)

            Oils 3 (2)

            Legumes (e.g., soy and other beans) 71 (6)

            Fish 15 (1)

            Meat (including poultry) 3 (less than 1)

            Eggs 1 (less than 1)

            Dairy less than 1 (less than 1)

            Vegetables

            Sweet potatoes 849 (69)

            Other potatoes 2 (less than1)

            Other vegetables 114 (3)

            Fruit less than 1 (less than 1)

            Seaweed 1 (less than 1)

            Pickled vegetables 0 (0)

            Foods: flavors & alcohol 7 (less than 1)

            Data derived from analysis of U.S. National Archives, archived food records, 1949 and based on survey of 2279 persons.

            Some points

            Their diet was 85% carb, and 6% fat. Sweet potatoes (a Japanese sweet potato) made up almost 70% of their calories. Nuts were less than 1% of calories (the equivalent of 1/10 of an ounce a day) Oil was less than 2% of calories (which is about 1 tsp a day) and sugars were less than 1% of calories (less than a tsp a day)

            The total animal products including fish was less than 4% of calories which is less then 70 calories a day. That is the equivalent of around 2 oz of animal products or less a day




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    1. Jkr: Yes, you are right, but that is not the whole story. It is important to keep in mind a phenomenon called bio-accumulation. What this means is that pollutants accumulate/get more concentrated the higher up the food chain you go.

      This is a general principal, so I would guess that there are plenty of exceptions. But in general, what this means is that you can minimize your exposure as much as possible by eating lower on the food chain – ie, eating plants rather than animals like fish.

      Hope that helps.




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    2. Most of the persistent organic pollutants are fat soluble. They accumulate more in organisms with high fat… vegetables, fruit, complex carbohydrates and beans are low in fat. The point Thea makes below is a good one. Bioaccumulation occurs naturally but is worse in commercial animal feeding practices where the by catch of fish and products from slaughtering operations are fed back to animals. You want to make sure that you wash your produce to remove any residual pesticides or chemicals.




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    1. Most likely so you can get sick, go to the hospital and give them money to keep you staying sick by taking a bunch of their “medicine”.. Its all about $$$

      Also, its not necessarily consuming seafood that is bad, (free of contaminations, it’s good for you!) but humans have polluted this world soo badly, in this particular case, the seafood..which comes from water… and we all know how much the water has been contaminated.. even worse now, hundreds of tons of contaminated water from the fukushima nuclear reactor are being dumped into the pacific ocean. Nuclear experts are telling US gov’t to test west coast waters and pacific seafood sold in the US, yet they refused to do so. Why would they refuse? There’s so much the mainstream media is keeping from you, but if you keep searching for answers in the right places, you will find.. keep in mind, you definitely will never find any truths from government sources, since they tried to convince people at one point that consuming any contaminated fish is safe.




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  6. The Zhang reference says that seafood is protective against diabetes. For oily fish it says for every 80 grams consumed results in a 20 percent decrease in type 2 diabetes. I am going to look at the other references more clearly now.




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  7. I guess Dr. Gregor has not heard of all of the “peer review” studies that have been done showing the benefits of “DPA” (a component of Omega 3 fatty acids) that were done “which did not rely on Greenland eskimo heart disease reports”.Eg. DPA lowers the risk of acute coronary events by 44%, DPA prevents formation of tumor-feeding blood vessels, DPA inhibits platelet aggregation better than DHA, DPA plays a role in slowing down dementia, DPA reduces genetic inflammation, DPA reduces genetic-based fat production, DPA & DHA reduce plaque formation.

    I learned this from one who, for “decades”, has worked with a Scientific Advisory Board (probably the very first scientific advisory board ever formed–by the company that coined the concept of a SAB). These scientists are of such high caliber that they always receive invitations to attend the most prestigious meetings “where new science breaks” The Greenland Eskimo data is “old hat” as far as they’re concerned. These scientists “cite studies done with people”, not just examine Greenland Eskimo data.

    As for the “pollutants”, this company (GNLD) is a “world leader” in product analysis and manufacture (has access to the most advanced laboratories worldwide), and is WELL CAPABLE of analyzing fish components for ANY toxin. They have a tolerance of 0% (anything detectible is DISCARDED).

    I honestly don’t know where this guy gets his data from, but sometimes I wish people would simply stop making generalizations, and talking out of their butts.




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    1. “I sometimes wish people would simply stop making generalizations, and talking out of their butts.”
      Amen!. And you believe everything about fish oil you are told by people who make their living selling fish oil? You don’t think that they may possibly have a conflict of interest?




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  8. My girlfriend and I, we take vegan DHA supplements because we’re thinking about having a child. Will the vegan DHA – an Omega 3 fatty acid – put us at risk of developing diabetes?




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  9. Good lord,

    The asian culture thrives on fish, and look at them. Before anyone says “they have diabetes too”, that only started 25 years ago with the introduction of many Western Fast food traditions. Beyond that, they have us beat in health by a nautical mile.




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  10. this article is a joke. study doctor jack kruse. I’ve been eating raw meats and fish for a year now and my blood tests are far better than any vegan I’ve ever known, not to mention professional athletes.




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    1. I think the joke’s on you. Try Googling “Jack Kruse quack”.

      And yeah, the guy on the Twinkie Diet got really good test results too ….




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      1. Just looked at it, the people complaining about kruse are the simpletons who can’t grasp what he is saying at a quantum level, and no, the guy that ate twinkies did not have good test results. Lol.




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  11. With vegan diet, how much fat should I consume? Dr. Barnard suggests very very fat intake, not even olive oil, avocado or walnuts. What do you think, Dr. Greger?




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  12. What about eating boiled oysters? They should have much less heavy metals than predatory fish. And most of the heavy metals are in the hard part of oysters that humans do not eat.
    I just orderer some “Crown Prince Natural, Boiled Whole Oysters, Packed In Water, 8 oz (226 g)”. I plan to eat oysters to get more copper. My Blood Ceruloplasmin which measures copper is low and eating cashew nuts does not seem to help, although cashew nuts in average contain a lot of copper. http://nutritionfacts.org/topics/oysters/




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  13. I am hoping Dr. Gregger or someone can reconcile why the Pescatarian group which also inlcuded egg/dairy eaters: “10% are pesco-vegetarian (Eat fish, milk and eggs but no red meat or poultry)” in the Adventist Health Studies lived the longest.

    Everything I read here (and in other areas) indicates fish is as bad as meat in many areas. Thus, the Adventist results contradict this as the “fish-eaters” outlived the Vegans

    “The adjusted hazard ratio (HR) for all-cause mortality in all vegetarians combined vs non-vegetarians was 0.88 (95% CI, 0.80–0.97). The adjusted HR for all-cause mortality in vegans was 0.85 (95% CI, 0.73–1.01); in lacto-ovo–vegetarians, 0.91 (95% CI, 0.82–1.00); in pesco-vegetarians, 0.81 (95% CI, 0.69–0.94); and in semi-vegetarians, 0.92 (95% CI, 0.75–1.13) compared with nonvegetarians.”

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4191896/

    Am I missing something as this large trial of comparably matched subjects contradicts Dr. Greggor and other citations? Thank you!




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    1. Hi dtraist, I agree, you are interpreting the data correctly. The thing I think is important to realize is that even in the non vegan groups the consumption of animal products is on average only about two servings per week which is significantly less than what the average meat eater would consume. So in effect these people still eat a mostly plant based diet. Now when you couple that with the other positive lifestyle factors that this group embodies like being physically active, low stress, community support etc. it essentially negates any of the potentially negative effects that animal products may possess. I often have patients who are resistant to giving up all animal products and I use this study as an example and tell them that if they are able to get everything else in their life right, and only eat animals once or twice a week they might be able to get away with it. (of course this is also provided they don’t already have some chronic illness they are trying to overcome…which by the way, is most often not the case or they wouldn’t be seeing me).




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      1. Thank you payoung. So if someone if overall healthy: not overweight, exercises everyday, no diseases, etc., but wants to think about longetivy, the question then is: Is he/she better off being totally vegan or eating a bit of fish like the Adventists since that group had longer lives? Or in Blue Zones, all groups ate small amounts of meat. You mention a small amount of meat is better than the standard American diet. I agree, but what about vs. a Vegan diet? Thank you very much!




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        1. There are a couple of points I would make:
          1) These studies were done on populations who lived these lifestyles their whole lives. That’s very different from a person (like me) who ate the standard American diet for 20 or 30 or more years and then switched to a WFPBD. That person like me, most probably already has the remnants of chronic disease whether or not it has been diagnosed. That person’s body is much less likely to be able to compensate for the occasional meal containing animal products. I think we need to be careful when applying the results of these studies to our own lives unless of course our lifestyles have been the same as those in the studies for our entire lives.
          2) These are population studies which by design look at averages. So they look at the average longevity within each group. This means there were people above and below the average. We can’t have an accurate sense for where we as an individual would fit on the curve unless we look at all the other contributing factors (ie- genetics, environmental factors etc). So we have to be careful about trying to apply these results to us individually.
          3) So do these studies really tell us anything? Yes they do. They tell us in general what’s required to attain longevity (ie: living healthy into your 9th or 10 decade) and any of these lifestyles will achieve that given they are consistently practiced throughout your lifetime. So the difference in the longevity results in these populations is not the difference between dying at age 60 vs. dying at age 95. Its more like the difference between dying at 95 and dying at 100.

          I like to use the following analogy personally as well as with my patients. I look at my overall health as a bank account. Any time I do things that are health promoting I’m making a deposit and I’m adding to my potential longevity. Any time I do something that is not health promoting I’m making a withdrawal. Just like any bank account you have to make more deposits than withdrawals in order to not be overdrawn. Animal products count as a withdrawal because they cost your body in resources far more than they contribute. If you’ve lived your life making consistent deposits then it may be affordable for you to eat an animal product once or twice a month. But if you spent the first 20, 30, 40 or more years of your life making more withdrawals than deposits, especially if you have already been diagnosed with a chronic disease, you can’t afford to make any withdrawals and expect to have longevity.
          Finally I’d like to say, if you are someone like me, who enjoyed eating animals for many years it becomes a very slippery slope when you decide you are going to eat just a small amount. It starts out as twice a month and before you know it its twice a week then once a day and without even realizing, your account is overdrawn.
          Hopefully this helps you decide how to apply the information from the longevity studies to your own life and circumstances.




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