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.
Most persistent industrial pollutants, like organochlorine pesticides such as DDT and PCBs, were banned several decades ago, and dioxin emission is strictly regulated. However, we’re still exposed to these chemicals through several routes, the major source of which is contaminated food––especially fatty animal products such as fish, meat, and milk. When we eat these chemicals, they get primarily stored in our own fatty tissue, where they slowly leach out into our bloodstream. But better in our fat than in our brain or other vital organs. Having more body fat may actually play a protective role by sequestering the toxins away. But they can come spilling out when we lose weight.
Body weight loss increases the concentrations of potentially toxic pollutants in obese individuals. Of the 19 pollutants studied, they all went up––15 significantly so. Every study that has looked at it found increased blood levels of toxic pollutants accompanying weight loss, whether induced by a diet or bariatric surgery: increases between 14 percent and 388 percent with a large enough loss. The more weight that’s lost, the higher the pollutant levels climb, because all those chemicals stored in your fat over all those years come spilling out.
The theoretical concern is that if released into the blood at a faster rate than they are cleared, the levels of these compounds could become toxic, causing side effects, such as sweating, headache, and nausea. But the opposite happened when PCB-poisoned patients were fasted. In 1979, about 2,000 people in Taiwan were exposed via an industrial accident that contaminated rice oil, leading them to have a higher body toxicity burden than even long-time consumers of seafood. But after a modified fasting regimen, all 16 patients they tried it on showed improvements, with some enjoying dramatic relief of their sufferings. But this was after just a few days of fasting, so, they couldn’t have really lost much body fat. And, they didn’t measure PCBs before or after. So, it’s not clear they were experiencing some sort of detox, nor what relevance this has for people who haven’t been acutely poisoned.
The initial rise in pollutant levels in the first year of weight loss may eventually stabilize or fall. Check out what happened in Biosphere 2, a remarkable experiment designed to be a completely closed ecosystem, the longest sustained period of humans isolated in a confined environment on record. But due to crop failures, it turned into a two-year experiment of calorie restriction. They all lost about 25 pounds in the first six months and stabilized there. And, while the levels of PCBs and a DDT metabolite known as DDE initially went up, they appeared to start coming back down. But that initial spike is quite a jump. That’s one of the reasons health authorities recommend women don’t try to slim down during breastfeeding. For example, here’s a woman whose breast milk levels jumped up after she had fasted and lost about 20 pounds.
Because fat is mobilized into breast milk, the secretion of human milk is a major way these pollutants are eliminated from the mother’s body. Breast is still best regardless, but you can keep your levels lower by not going out of your way to lose weight until after breastfeeding is finished.
What can one do to help flush the contaminants during weight loss? One of the reasons the pollutant levels in the Biosphere subjects eventually dropped is because they were eating a high-fiber diet centered around fruits, whole grains, beans, nuts, and vegetables. And we know that fiber can bind to these pollutants, and potentially flush them out of the body. So, when losing weight, eating lots of whole grains may be important to increase the elimination of pollutants, while, of course, cutting down on animal fat, including fish, so you don’t pile on extra at the same time.
What about just eating some Pringles? What was the dietary intervention in this randomized trial to decrease the body burden of pollutants? Subjects were randomized to 24 fat-free Pringles a day, or regular Pringles. What?! Why? It all started with this crazy case report of a guy heavily contaminated by PCBs who managed to rid himself of 90 percent by losing weight eating potato chips made out of the fake fat olestra, which doesn’t get absorbed, and so appears to pull pollutants out of bloodstream into the stool for elimination. It works in mice, increasing the excretion of hexachlorobenzene 30-fold, and cutting the levels in their brains in half. But in people, the drop in PCB blood levels with the olestra Pringles was not statistically significantly greater. And, for some reason, LDL [bad] cholesterol levels shot up 28 points in the olestra group. And, while olestra and drugs like cholestyramine may absorb pollutants, and remove them from your system, they also may cause you to dump fat-soluble vitamins. So, to get the best of both worlds, losing pollution without losing vitamins, fiber-rich foods may be our best choice.
Instead of olestra supplementation to detox, why not try to not tox so much in the first place?
Please consider volunteering to help out on the site.