Transcript: Pollutants in Salmon and Our Own Fat
This nationwide study on industrial toxins and diabetes was published in 2006. Since then, Harvard researchers reported a link between persistent pollutants like hexachlorobenzene and diabetes in their Nurses' Health Study. This is supported by an analysis they did of six other studies published since 2006 that showed the same thing. They 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.
Especially farmed salmon, perhaps the greatest source of dietary pollutants, averaging nearly ten times the PCB load of wild-caught salmon.
But wait a second. Since many of these chemicals were banned in the 70s, the levels inside people have been going down, whereas the rates of diabetes have been shooting straight up, so how could pollutant exposure be causing diabetes? This puzzle may be explained by the epidemic of obesity in the U.S. They showed that the association between these toxins and diabetes was much stronger among obese subjects compared with that of 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.
And 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 not only consume high concentrations of pollutants, but some of these chemicals might take between 50 and 75 years to clear from the body.
What about the mercury in fish? Diabetics do seem to have higher mercury levels in their body. Here are the mercury levels in hair samples from healthy people; here are the levels in patients with diabetes or hypertension. But mercury alone does not seem to increase diabetes risk. It may be the simultaneous exposure to both dioxins and mercury that increases risk, so it should concern us that the safety limits for dioxins and mercury individually may underestimate the risk when they’re consumed together in seafood.
And then once we get diabetes, higher pollutant levels may be associated with a higher risk of diabetic complications.
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 polluted our world we can’t escape exposure completely. You got to eat something, but some foods are more contaminated than others. 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 you most commonly find in supermarkets and restaurants.
You hear about advisories warning pregnant women to avoid the consumption of food containing elevated levels of pollutants and mercury, but 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.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.
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