The Best Dietary Detox

Michael Greger M.D. FACLM · September 4, 2024 · Volume 66

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By eating at a lower rung on the food chain, those choosing plant-based diets suffer less exposure to the industrial pollutants that bioaccumulate up the ladder.

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We lack robust safety data on most of the estimated 30,000 chemicals in wide commercial use registered under the U.S. Toxic Substances Control Act. But the greatest concern may lie in the long-banned legacy chemicals that continue to contaminate the food supply, known as PLOPs—persistent lipophilic organic pollutants. These include dioxins, PCBs, and insecticides such as DDT. How do we drop the PLOPs? Today, most DDT comes from meat, particularly fish. The oceans are essentially humanity’s sewer; everything eventually flows into the sea. Hexachlorobenzene is another banned pesticide that may be carcinogenic, but is more evenly spread among animal food sources, whereas PCBs are also mostly a fish thing.

PCBs are a different set of banned chemicals, once widely used as insulating fluid in electrical equipment. A study of more than 12,000 food and feed samples across 18 countries found that the highest PCB contamination was found in fish and fish oil, followed by eggs, then dairy, then other meats. Salmon may have the highest concentration (with farmed-raised salmon having consistently higher contaminant levels than wild-caught), followed by canned tuna. But since people don’t tend to eat a lot of fish, other meat may be the largest exposure for most people. The lowest contamination was found at the bottom of the food chain in plants, which can average seven to 20 times fewer overall PCB and dioxin-like chemicals, compared to ocean or freshwater fish.

That’s one of the advantages to eating more plant-based in the modern world. By eating from the lowest rung of the food chain, we suffer less exposure to the industrial pollutants that bioaccumulate up the ladder. Every year in the United States, billions of pounds of slaughterhouse by-products are produced, the vast majority of which are fed right back to the farm animals––particularly chickens, which can recycle toxic heavy metals and industrial chemicals back into the food supply. Lead builds up in bones, and mercury attaches to the protein (which is why egg whites can have four times more mercury than do yolks). Most of the lead in the bone meal passes right through the animals into their waste, but then producers can take that waste—cow, pig, and chicken feces—and feed it back to the animals again. So, you can see how the levels of contaminants might build up in their bodies, even when the animals themselves may be natural herbivores.

Lower pollutant levels may help explain why those eating plant-based appear to be less likely to develop all forms of cancer combined, but their role in longevity is unknown. Heavy metals such as lead appear to accelerate human aging, and most population studies have suggested a strong association between exposure to higher levels of environmental pollutants and shorter telomeres. However, only a few have been found to be significantly related to premature death. One such contaminant is the long-banned pesticide beta-hexachlorocyclohexane. Higher levels in the blood correlate with higher all-cause mortality.

A study of the breast milk from two sisters with different dietary habits offered a clue on a way to lower exposure. The levels of beta-hexachlorocyclohexane, as well as PCBs, DDT, and another banned pesticide dieldrin were much lower in the breast milk from the vegetarian mother than the milk of her sister, who was also breastfeeding at the time, but included meat in her diet. Studies of the pollutants in breast milk of vegetarians dating back over 30 years have found the average levels of some pollutants were 50 to 100 times lower in the vegetarians compared to the national average. In fact, for the six out of seven pollutants they looked at, there wasn’t even an overlap in the range of scores; the highest vegetarian value was lower than the lowest value obtained in the general population.

Chlorinated PCBs have also been associated with increased mortality risk, suggesting that we should minimize exposure, which basically means a reduction in animal fats. The blood of those eating strictly plant-based diets were found to be “signiﬁcantly less polluted” regarding a whole series of PCBs, including those found in the study to be associated with increased mortality, but their lower levels of β-hexachlorocyclohexane did not reach statistical significance. Those eating plant-based diets have also been found to have markedly lower levels of dioxins in their bodies, as well as decreased contamination with flame-retardant chemical pollutants known as PBDEs. It’s no surprise, given the sources of flame retardants in the food supply. Again, even though the highest levels of flame retardants in the U.S. food supply have been found in fish, the primary source of intake for most Americans is poultry, just because we eat so much chicken, followed by processed meat. For some reason, U.S. chickens are about ten to twenty times more contaminated than chickens tested from some other countries. The longer people go without meat, the lower their levels appear to fall.

Eating healthier can also reduce the concentrations of heavy metals in your body. The levels of mercury in the hair of those eating more plant-based diets were found to be up to ten times lower than of those who ate fish, but you don’t know if it’s cause and effect until you put it to the test. Within three months of switching to a plant-based diet, the levels of mercury, lead, and cadmium growing out in your hair appear to drop significantly (but build back up when meat and eggs are added back into the diet). Unlike heavy metals, though, some organochlorine pollutants can stick around for decades.

A USDA examination of the levels of dioxin-like compounds in U.S. meat and poultry indicated a possible concern for U.S. public health, but really mostly for children. The typical U.S. adult daily exposure in meat was well below the EPA established safety limit. Only children chronically consuming the average daily servings of meat or poultry with the highest levels might exceed it.

Taking all 33 chemical pollutants in meat shown to be potentially carcinogenic into account, some European toxicologists suggest limiting children’s consumption of beef, pork, and chicken to a combined total of no more than five servings a month; so, an average of no more than like one serving of meat every six days or so. In Europe, lamb is the most contaminated, and the recommendation calls for adults to eat no more than a single serving every four or five months.

Surprisingly, as I explored in a previous video, the consumption of organic meat does not seem to diminish the cancer-causing potential associated with the PLOPs in meat. All samples were found to be contaminated, with minimal differences between meat raised organic versus conventional.

What can we do to reduce exposure? Eat high-fiber foods, as fiber can bind to some of the contaminants, and flush them out of the body. Exercise, as blood levels of persistent pollutants have been found to be lower among physically active individuals, perhaps due to sweating, or due to a potential boost in detoxing enzymes, or increased clearance through the bile, at least in rats.

Given current contamination levels “meat consumption in general … should be significantly modified downward, as much and as soon as possible,” though until then, consumers can reduce exposures to dioxins and dioxin-like compounds like PCBs by trimming fat when preparing meat, and further trim and thoroughly drain fat after cooking.

The Best Dietary Detox is to not tox in the first place.

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Motion graphics by Avo Media

Doctor's Note

The video on meat that I mentioned is Is Organic Meat Less Carcinogenic?

I previously touched on Fasting to Detox.

In The Wrong Way to Detox, I talk about the transfer of pollutants from mothers to their children.

For more on how we acquire toxins in the first place, see:

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