Estrogen in Meat, Dairy, and Eggs










More on xenoestrogens in:

In health,
Michael Greger, M.D.


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Is Insecticidal GMO Corn Safe?


Recently the prominent science journal Nature editorialized that we are now swimming in information about genetically modified crops, but that much of the information is wrong--on both sides of the debate. "But a lot of this incorrect information is sophisticated, backed by legitimate-sounding research and written with certitude," adding that with GMOs, "a good gauge of a statement's fallacy is the conviction with which it is delivered."

To many in the scientific community, GMO concerns are dismissed as one big conspiracy theory. In fact, one item in a psychological test of belief in conspiracy theories asked people if they thought food companies would have the audacity to be dishonest about genetically modified food. The study concluded that many people were cynical and skeptical with regard to advertising tricks, as well as the tactics of organizations like banks and alcohol, drug, and tobacco companies. That doesn't sound like conspiracy theory to me; that sounds like business as usual.

We must remember there is a long legacy of scientific misconduct. Throw in a multi-billion dollar industry, and one can imagine how hard it is to get to the truth of the matter. There are social, environmental, economic, food security, and biodiversity arguments both pro and con about GMOs, but those are outside my area of expertise. I'm going to stick to food safety. And as a physician, I'm a very limited veterinarian--I only know one species (us!). So, I will skip the lab animal data and ask instead: What human data do we have about GMO safety?

One study "confirmed" that DNA from genetically modified crops can be transferred into humans who eat them, but that's not what the study found, just that plant DNA in general may be found in the human bloodstream, with no stipulations of harm (See Are GMOs Safe? The Case of Bt Corn).

Another study, however, did find a GMO crop protein in people. The "toxin" was detected in 93 percent of blood samples of pregnant women, 80 percent of umbilical cord blood samples, and 69 percent of samples from non-pregnant women. The toxin they're talking about is an insecticidal protein produced by Bt bacteria whose gene was inserted into the corn's DNA to create so-called Bt-corn, which has been incorporated into animal feed. If it's mainly in animal feed, how did it get into the bodies of women? They suggest it may be through exposure to contaminated meat.

Of course, why get GMO's second-hand when you can get them directly? The next great frontier is transgenic farm animals. A genetically modified salmon was first to vie for a spot at the dinner table. And then in 2010, transgenic cows, sheep, goats and pigs were created, genetically modified for increased muscle mass, based on the so-called mighty mouse model. Frankenfurters!

But back to children of the corn and their mothers. When they say it's a toxin, it's a toxin to corn worms, not necessarily to people. In fact I couldn't find any data linking BT toxin to human harm, which is a good thing since it's considered one of the few pesticides considered so non-toxic that it's sprayed on organic fruits and vegetables.

For more on on the public health implications of genetically modified crops, see:

I did a similar "controversial issue" video series on gluten. See:

For those interested in the genetic engineering of livestock, I published a few papers myself on the topic:

In health,
Michael Greger, M.D.


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Dietary Estrogens and Male Fertility


In my video, The Role of Diet in Declining Sperm Counts, I discussed the association between high saturated fat intake and reduced semen quality. But what's the connection? One of the most recent papers on the topic found that a significant percentage of the saturated fat intake in the study was derived from dairy products. Residues of industrial chemicals may bioaccumulate up the food chain into animal fat, and some of these lipophilic (fat-loving) chemicals may have hormone-disrupting abilities.

The U.S. Environmental Protection Agency performed a national survey of persistent, bioaccumulative, and toxic pollutants in the U.S. milk supply (highlighted in my video, Dairy Estrogen and Male Fertility). The EPA team noted that since milk fat is likely to be among the highest dietary sources of exposure to these pollutants, it's important to understand the levels in the dairy supply. The team tested milk from all over the country and found a veritable witches brew of chemicals. They estimate that dairy products alone contribute about 30% to 50% of our dioxin exposure. And "like dioxin, other toxic pollutants tend to be widely dispersed in the environment, bioaccumulated through the food chain and ultimately result in low-level contamination in most animal fats."

This may explain higher pollutant concentrations in fish eaters. Xenoestrogens like polychlorinated biphenyls (PCBs) are associated with the fats of fish or animal flesh and cannot be fully removed by washing and cooking, and so can accumulate in our fat, too. Xenoestrogens are chemicals with demasculinizing or feminizing effects. But even in a non-polluted world, animal foods also have actual estrogen, which are unavoidable constituents of animal products. All foodstuff of animal origin contains estradiol, which is at least 10,000-fold more potent than most xenoestrogens. Dietary exposure--meat, dairy products and eggs--to these natural sex steroids is therefore highly relevant, as the hormones in these animals are identical to our own.

Estrogens are present in meat and eggs, but the major sources are milk and dairy products. By drinking a glass of milk, a child's intake of estradiol is 4,000 times the intake of xenoestrogens in terms of hormone activity. Modern genetically-improved dairy cows can lactate throughout their pregnancy. The problem is that during pregnancy, estrogen levels can jump as much as 30-fold.

Cheese intake has specifically been associated with lower sperm concentration, whereas dairy food intake in general has been associated with abnormal sperm shape and movement. Lower sperm concentrations by themselves may just represent a potential suppression of sperm production due to higher estrogen levels, but abnormal shape and movement suggests that dairy intake may be implicated in actual direct testicular damage.

While milk products supply most of our ingested female sex steroids, eggs are a considerable source as well, contributing about as much as meat and fish. This could be expected, as eggs are produced directly in the hens' ovaries.

Meat may also contain added hormones. In the U.S. anabolic sex steroids may be administered to animals for growth promotion, a practice banned in Europe twenty-five years ago. A study in New York found progressively lower sperm counts associated with processed meat consumption. However, similar studies in Europe after the ban found the same thing, so it may not be the implanted hormones, but rather a consequence of other meat components, such as the saturated fat raising cholesterol levels.

We've known for decades that men with high cholesterol levels show abnormalities in their "spermiograms": decreased sperm concentration, about a third of the normal sperm movement, and half the normal sperm shape. Twenty-five years later, we're finding the same thing. In the largest study to date, higher blood cholesterol levels were associated with a significantly lower percentage of normal sperm. Cholesterol was also associated with reductions in semen volume and live sperm count. These results highlight the role of fats in the blood in male fertility, and should be of concern given the rising prevalence of obesity and cholesterol problems. Although a healthier diet may be associated with healthier sperm counts, cholesterol-lowering statin drugs do not seem to help.

What about the phytoestrogens in soy? See The Effect of Soy on Precocious Puberty.

More on hormones in dairy in:

Neurotoxic chemicals in the dairy supply have been blamed for neurological conditions as well. See my video Preventing Parkinson's Disease with Diet.

In health,
Michael Greger, M.D.


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Children’s Supplements Found Contaminated With Pollutants

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A number of case-control studies have found that giving kids cod liver oil supplements may increase their risk of asthma later in life. Case-control studies are done by asking about past behavior in cases (those with asthma) versus controls (those without asthma) to see if certain past behaviors are more likely among the disease group. The problem is that asking people to remember what they were doing years ago, when most people can't remember what they had for breakfast last week, is unreliable. When interpreting the results from case-control studies, we also can't rule out something called reverse causation. Maybe cod liver oil doesn't lead to asthma, but asthma led to the use of cod liver oil.

It would therefore be nice to see a cohort study. In a cohort study, researchers would take people without asthma and follow them over time to see if those taking cod liver oil are more likely to develop it. Because people without the disease and their diets are followed over time, cohort studies bypass the problems of recall bias and reverse causation.

In 2013, we finally got one such study. 17,000 people free of asthma were followed over 11 years. Researchers knew who was taking cod liver oil and who wasn't, and then sat back and watched to see who got asthma over the subsequent 11 years. The researchers found that cod liver oil intake was indeed significantly associated with the development of asthma. They thought it might be the excessive vitamin A in the cod liver oil that was causing the problem, but there are also a number of substances in fish oil we may not want our children exposed to.

Researchers from Philadelphia University, highlighted in my video PCBs in Children's Fish Oil Supplements, recently looked at 13 over-the-counter children's dietary supplements containing fish oil to assess potential exposure to PCBs, toxic industrial pollutants that have contaminated our oceans. PCBs were detected in all products. Could we just stick to the supplements made from small, short-lived fish like anchovies instead of big predator fish like tuna to reduce the impact of biomagnification? Or use purified fish oils? No, the researchers found no significant difference in PCB levels whether the supplements were labeled as molecularly distilled or how high up the food chain the fish were.

The researchers concluded that while children's dietary supplements containing the long-chain omega-3's from fish oils may claim to benefit young consumers, "daily ingestion of these products may provide a vector for contaminant exposure that may off-set the positive health effects." What positive health benefits are they talking about?

Researchers publishing in the journal, Early Human Development, found that infants given DHA-fortified formula may have better development of their eyes and brains compared to infants getting non DHA-fortified formula. What was the source of the DHA? Not fish, but algae-derived DHA. In that way we can get the benefits of omega 3's without the contaminant risks. But of course, breast milk is the gold standard, significantly better than either of the formula fed infants. So the best source of omega-3's is mom.

It's bad enough when supplement manufacturers exploit adults when they're sick and vulnerable with pills that are often useless or worse, but taking advantage of our parental drive to do what's best for our children with contaminated products that may make them sick, makes me sick.

More on supplements in:

And speaking of which, Is Fish Oil Just Snake Oil?

Also check out these videos on fish oil and DHA: Omega-3's and the Eskimo Fish Tale and Should We Take EPA and DHA Omega-3 For Our Heart?

What about omega 3's for our child's growing brain? See my video Mercury vs. Omega-3s for Brain Development

We can also be exposed to PCBs in food. See Food Sources of PCB Chemical Pollutants.

More on the polluted aquatic food chain in:

What can we do to lower the risk of childhood asthma and other allergic-type diseases? See:

In health,
Michael Greger, M.D.


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Dioxins in U.S. Farm-Raised Catfish

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Other pollutants in our food supply and how to avoid them:


In health,
Michael Greger, M.D.


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Should We Take Chlorella to Boost Natural Killer Cell Activity?

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Bile Acids and Breast Cancer

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Why do constipated women appear to be at higher risk for breast cancer? The results of a 1989 study out of the American Journal of Public Health suggested a slight increased risk of breast cancer for both decreased frequency of bowel movements and firm stool consistency. Women who had three or more bowel movements a day appeared to cut their risk of breast cancer in half. This could be because constipation means a greater contact time between our waste and our intestinal wall, which may increase the formation and absorption of fecal mutagens--substances that cause DNA mutations and cancer--into our circulation, eventually ending up in breast tissue.

The concept that more frequent bowl movements decrease breast cancer risk dates back more than a century, where severe constipation, so-called "chronic intestinal stasis," was sometimes dealt with surgically. Figuring that the colon was an inessential part of the human anatomy, why not cure constipation by just cutting it out? After the surgery, they noticed that potentially precancerous changes in the breasts of constipated women seemed to disappear.


We know that even the non-lactating breast actively takes up chemical substances from the blood. We also know that there are mutagens in feces. It is not unreasonable to suggest that potentially toxic substances derived from the colon have damaging or even carcinogenic effects upon the lining of the breast. Toxic substances like bile acids. Bile acids were first shown to promote tumors in mice in 1940, but subsequent experiments on rats led to the mistaken belief that bile acids just promoted existing cancers and couldn't initiate tumors themselves. However, there is a fundamental difference between the rodent models and human cancer. Rats only live a few years while humans can live dozens, so the opportunity for cancer causing mutations may be at least 30 times greater in humans. We now have at least 15 studies that show that bile acids can damage DNA, strongly suggesting they can initiate new cancers as well.

Bile acids are formed as a way of getting rid of excess cholesterol. Our liver dumps bile acids into the intestine for disposal, assuming our intestines will be packed with fiber to trap it and flush it out of the body. But if we haven't been eating enough fiber-rich whole plant foods, bile acids can be reabsorbed back into the body and build up in the breast.


Slowed colonic transit can increase bile acid levels. Therefore, to decrease absorption of bile acids, we can speed up the so-called "oro-anal transit time," the speed at which food goes from mouth to toilet, by eating lots of fiber. A diet packed with plants greatly increases bile acid excretion.


I touched on this in my live presentation From Table to Able: Combating Disabling Diseases with Food, but what I didn't get to discuss is the relative bile acid binding abilities of different foods. I cover that in my video Which Vegetable Binds Bile Best?


Fiber may also help women remove excess estrogen from their body. See my video Fiber vs. Breast Cancer. For more on the wonders of fiber, see Dr. Burkitt's F-Word Diet.


In health,
Michael Greger, M.D.


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Salmon May Be the Greatest Source of Dietary Pollutants

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In my video Diabetes and Dioxins, I explored a nationwide study that found a strong dose-response relationship between industrial toxins and diabetes. Since then, Harvard researchers have reported a link between persistent pollutants like hexachlorobenzene and diabetes in their Nurse's Health Study (See Food Sources of Perfluerochemicals). This is supported by an analysis they did of six other studies published since 2006 that showed the same thing. The Harvard researchers 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." Farmed salmon specifically is perhaps the greatest source of dietary pollutants, averaging nearly ten times the PCB load of wild-caught salmon.

Wait, isn't there a flaw in this argument? Since many of these chemicals were banned in the 70's, the levels inside people have been going down, whereas the rates of diabetes have been shooting straight up. Therefore, how could pollutant exposure be causing diabetes? This puzzle may be explained by our epidemic of obesity. The nationwide study found that the association between these toxins and diabetes was much stronger among obese subjects than among 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.

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 end up retaining these chemicals in their bodies for 50 to 75 years.

Hexachlorobenzene in fish has been tied to diabetes; what about the mercury? A 1995 study highlighted in my video, Pollutants in Salmon and Our Own Fat, out of Japan found that diabetics do seem to have higher mercury levels in their body. Mercury alone does not seem to increase diabetes risk, though. It may be the simultaneous exposure to both dioxins and mercury that increases risk, so the safety limits for dioxins and mercury individually may underestimate the risk when they're consumed together in seafood.

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 contaminated our world, we can't escape exposure completely. You have to eat something. Some foods are more contaminated than others, though. 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 we most commonly find in supermarkets and restaurants.

We hear about advisories warning pregnant women to avoid the consumption of food containing elevated levels of pollutants and mercury, but as a public health journal article points out, 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."

For the existing links between seafood and diabetes risk, see Fish and Diabetes and I explored this concept of our own body fat as a reservoir for disease-causing pollutants in Diabetes and Dioxins.

More on hexachlorobenzene in my video Food Sources of Perfluorochemicals.

Our body has a tougher time getting rid of some toxins than others:

The best way to detox is to stop toxing in the first place.

-Michael Greger, M.D.


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Dr. Greger’s 2015 Live Year-in-Review Presentation

Food as Medicine







You can watch it at no cost online, but it is also available on DVD through my website or on Amazon. If you want to share copies with others, I have a five for $40 special (enter coupon code 5FOR40FAM). All proceeds from the sales of all my books, DVDs, downloads, and presentations go to the 501c3 nonprofit charity that keeps NutritionFacts.org free for all, for all time. If you want to support this initiative to educate millions about eradicating dietary diseases, please consider making a donation.

After you've watched the new presentation, make sure you're subscribed to get my video updates daily, weekly, or monthly to stay on top of all the latest.

-Michael Greger

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Dioxins Stored in Our Own Fat May Increase Diabetes Risk

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Finding higher diabetes rates among those heavily exposed to toxic pollutants--such as those exposed to Agent Orange, chemical plant explosions, toxic waste dumps, or heavy metals in fish from the Great Lakes--is one thing. Would the same link be found in a random sampling of the general population? Yes. A strong dose-dependent relationship was found between the levels of these pollutants circulating in people's blood and diabetes. Those with the highest levels of pollutants in their blood stream had 38 times the odds of diabetes.

Interestingly, there was "no association between obesity and diabetes among subjects with non-detectable levels of pollutants." In other words, "obesity was a risk factor for diabetes only if people had blood concentrations of these pollutants above a certain level." We know obesity predisposes us to diabetes, but according to this study, highlighted in my video, Diabetes and Dioxins, this is perhaps true only if our bodies are contaminated with industrial pollutants. This finding implies that virtually all the risk of diabetes conferred by obesity is attributable to these pollutants, and that obesity might only be a vehicle for such chemicals. Could we be carrying around our own little toxic waste dump on our hips?

Now it's entirely possible that the six pollutants they looked at were not themselves causally related to diabetes. Rather, they could just be surrogates of exposure to a mixture of chemicals. After all, 90% of these pollutants in our diet come from animal foods. Except for individuals living or working around industrial sites where these chemicals were used or dumped, the most common source of exposure to PCBs is from diet, from foods of animal origin, especially seafood. The strong relationship the researchers found between certain pollutants and diabetes may just be pointing to other contaminants in animal products.

If these pollutants are particularly found in seafood, are people who eat fish at higher risk for diabetes? See my videos Fish and Diabetes, and Pollutants in Salmon and Our Own Fat.

For more on dioxins, see:

For more on PCBs, see:

These pollutants may also play a role in our rising epidemic of allergic diseases. See Alkylphenol Endocrine Disruptors and Allergies and Dietary Sources of Alkylphenol Endocrine Disruptors.

-Michael Greger, M.D.


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