With all the debate about whether fat in the diet is good or bad, one morsel getting lost in the discussion is that animal fat is a natural reservoir for environmental pollutants. Persistent Organic Pollutants (POPs) are largely hydrophobic, meaning they don’t dissolve well in water but they dissolve easily in fat. They also bioaccumulate, meaning they are found in higher, more concentrated amounts in animals higher in the food chain (such as tuna, salmon, fish-eating fowl, and farmed animals fed fish meal and other animal products), and, of course, ourselves:
“POPs are lipophilic chemicals that can pass through biological phospholipid membranes and bio-accumulate in fatty rich tissues of humans.”
Consumption of fat and cholesterol has been repeatedly linked to weight gain, arterial plaque buildup, blood glucose abnormalities, even cancer progression. Could it be the chemicals dissolved in that animal fat that are contributing to these ailments? Yes, says researcher Jerome Ruzzin from the University of Bergen in Norway:
Public Health Concern Behind The Exposure To Persistent Organic Pollutants And The Risk Of Metabolic Diseases, BMC Public Health, April 2012
“There is now solid evidence demonstrating the contribution of POPs, at environmental levels, to metabolic disorders. Thus, human exposure to POPs might have, for decades, been sufficient and enough to participate to the epidemics of obesity and type 2 diabetes.”
“The general population is exposed to sufficient POPs, both in term of concentration and diversity, to induce metabolic disorders. This situation should attract the greatest attention from the public health and governmental authorities.”
No mincing of words there!
What are POPs?
“Persistent organic pollutants (POPs), including dioxins, furans, polychlorinated biphenyls (PCBs), and organochlorine pesticides, are chemicals mainly created by industrial activities, either intentionally or as by-products . Because of their ability to resist environmental degradation, these substances are omnipresent in food products, and found all around the world, even in areas where they have never been used like Antarctica . Thus, virtually all humans are daily exposed to POPs.”
What foods contain the most POPs?
“In the general population, exposure to POPs comes primarily from the consumption of animal fat like fatty fish, meat and milk products; the highest POP concentrations being commonly found in fatty fish [15–26].”
Some diseases linked to POPs (from a variety of studies: humans, animals, cell models):
Bio-accumulation of PCBs has been linked to non-alcoholic fatty liver disease (NAFLD) and elevated blood pressure.
Animals exposed to environmental levels of POP mixtures through the intake of non-decontaminated fish oil (obtained from farmed Atlantic salmon) exhibited insulin resistance, glucose intolerance, abdominal obesity and NAFLD . In rats fed decontaminated crude salmon oil, which contained very low levels of POPs, these metabolic disturbances were almost absent.
The presence of POPs in farmed Atlantic salmon fillet was found to accelerate the development of visceral obesity and insulin resistance in mice.
Another important issue is the regulation of organochlorine pesticides, which are chemicals strongly linked to type 2 diabetes [29, 32, 33, 37, 44, 45] as well as breast and prostate cancer  and Parkinson disease 
It looks like we can’t get away from DDT, even though it was banned here in 1972:
“Not surprisingly, a recent US monitoring study revealed that DDT and its metabolites as well as endosulfan and aldrin, are still largely present in food, and daily consumed by humans.”
Children are at greater risk of exposure:
“Because of their high food intake per kilogram body weight required to maintain whole-body homeostasis and growth, children are likely to be at higher risk for environmental pollutant exposure. Not surprisingly, many scientific studies have highlighted that children are over-exposed to dioxins and dl-PCBs, and exceed the TDI of 2 pg/kg body weight.”
Finally, here’s a list of limits set by the European Union:
- Ruminants: 4.5 pg/g fat
- Poultry and farmed game: 4.0 pg/g fat
- Pigs: 1.5 pg/g fat
- Marine oils: 10 pg/g fat
You can see that the limit for marine oils is double that for fat from land animals. Why? They need to get together on this and create standards that apply across the board, and are based on public health, not commerce. Speaking of salmon, he says that “eating 1 g of fat from a fatty fish fillet could induce an exposure to 70 pg.”
What are Paleos eating? I mean, you can’t be Paleo and vegan at the same time. How do you avoid all these dissolved POPs?
Regulating vehicle emissions, pesticides, and industrial wastes is at odds with economic growth, which is why I think pollution and its attendant chronic disease load is here to stay.
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