What Happens When Pregnant Women Eat More Animal Protein

Are high-protein diets during pregnancy healthful or harmful? That question was answered about 40 years ago in the infamous Harlem Trial of 1976: a “randomized controlled trial of nutritional supplementation pregnancy, in a poor black urban population in the United States.” The study, which I discuss in my video The Effect of Animal Protein on Stress Hormones, Testosterone, and Pregnancy, “was begun when protein was commonly assumed to be deficient in the diet of the poor.” Had researchers actually analyzed their diets before they started, they would have realized that this wasn’t true, but why let facts get in the way of assumptions? So, the researchers split poor black pregnant women into three groups, each receiving one of the following treatments: (1) an extra 40 grams of animal protein a day, which is essentially a couple cans of Ensure, (2) an extra 6 grams of animal protein, or (3) no extra protein. Then they sat back and watched what happened. The high-protein group suffered “an excess of very early premature births and associated neonatal [infant] deaths, and there was significant growth retardation” in the babies who survived. More protein meant more prematurity, more deaths, and more growth retardation, which you can see reflected in the chart at 1:00 in my video.

What’s more, animal protein intake during pregnancy has been associated with children becoming overweight later in life and getting high blood pressure. The “offspring of mothers who reported eating more meat and fish had higher systolic blood pressure” in adulthood. This was part of another failed dietary intervention trial in which mothers were advised to eat a pound of meat a day. The increased weight gain and high blood pressure may be due to the obesity-causing chemical pollutants in the meat supply, as I’ve discussed in my video Animal Protein, Pregnancy, and Childhood Obesity, or the animal protein-induced rise in the growth hormone IGF-1. Or, it could be due to a steroid stress hormone called cortisol.

As you can see in the chart at 2:01 in my video, a single meal high in animal protein can nearly double the level of the stress hormone in the blood within a half hour of consumption, much more than a meal closer to the recommended level of protein. When subjects are given a meal of crab, tuna fish, and cottage cheese, the stress hormone level shoots up. If they’re instead given some barley soup and a vegetable stir-fry on rice, the stress hormone level goes down after the meal, as you can see at 2:27 in my video. Imagine eating meat-fish-dairy meals day after day. Doing so “may chronically stimulate” our stress response axis “and increase the release of vasoactive hormones” that could increase our blood pressure. And, all that extra cortisol release has been linked to increased risk for elevated blood levels of insulin, triglycerides, and cholesterol.

When men on a high-protein diet, “such as meat, fish, poultry, egg white,” were switched to a high-carb diet of bread, vegetables, fruit, and sugary junk, their cortisol levels dropped about a quarter within 10 days. At the same time, their testosterone levels shot up by about the same amount, as you can see at 3:09 in my video. High-protein diets suppress testosterone. That is why, if men eating plant-based diets begin to eat meat every day, their testosterone levels go down and some estrogens actually go up, and that’s why bodybuilders can get such low testosterone levels. It’s not the steroids they’re taking. If you look at natural bodybuilders who don’t use steroids, there is a 75 percent drop in testosterone levels in the months leading up to a competition. Testosterone levels were cut by more than half, which is enough to drop a guy into an abnormally low range, as you can see at 3:47 in my video. It’s ironic that they’re eating protein to look manly on the outside, but it can make them less and less manly on the inside. And, from an obesity standpoint, in general, a drop in testosterone levels may increase the risk of gaining weight and body fat. What does cortisol have to do with weight?

There’s actually a disease caused by having too much cortisol, called Cushing’s syndrome, which can increase abdominal obesity. Even in normal women, though, chronic stress and chronic high cortisol levels can contribute to obesity. What’s more, if they’re pregnant, high-meat and low-carb diets may increase cortisol levels in the moms, which can lead to inappropriate fetal exposure to cortisol, which, in turn, can affect the developing fetus, resetting her or his whole stress response thermostat and leading to higher cortisol levels in later adult life. This can have serious, life-long health consequences. Every maternal daily portion of meat and fish was associated with 5 percent higher cortisol levels in their children as much as 30 years later, though green vegetable consumption was found to be protective. Higher meat consumption, such as three servings a day compared to one or two, was associated with significantly higher cortisol levels, but eating greens every day appeared to blunt some of that excess stress response, as you can see at 5:12 in my video.

As well, the adult children of mothers who ate a lot of meat during pregnancy don’t only have higher stress hormone levels, they also appear to react more negatively to whatever life throws at them. Researchers put them through the Trier Test, which involves public speaking in front of a panel of judges, following by a live math exercise. You can see in my video at 5:36 a chart comparing the stress hormone responses in those whose moms ate less than two servings of meat per day, about two servings a day, or about two to three servings a day. Note that before the test started, the cortisol levels of the two groups eating less meat started out about the same, but their exaggerated cortisol response was laid bare when exposed to a stressful situation. The real-world effects of this are that after that sort of test, when people are given their own private snack buffet with fruits and veggies versus fatty, sugary, comfort foods like chocolate cake, guess who may eat less of the fruits and veggies? Those who have high chronic stress levels. “Cortisol has been implicated as a factor in motivating food intake” even when we aren’t really hungry.

It’s no surprise then that a woman’s animal protein intake during pregnancy may lead to larger weight gain for her children later in life—and maybe even for her grandchildren. “Remarkably, recent evidence suggests that the long-term consequences of adverse conditions during early development may not be limited to one generation, but may lead to poor health in the generations to follow, even if these individuals develop in normal conditions themselves.” Indeed, the diet of a pregnant mother may affect the development and disease risk of her children and even her grandchildren. Ultimately, these findings may shed light on our rapidly expanding epidemics of diabetes, obesity, and heart disease.


Whoa, there was a lot to unpack! Rather than break it up, since so much of it was tied together, as you could see, I compiled everything into this one, heftier piece. You may want to read this a second time and watch the video to absorb it all.

For more on how a woman’s diet during pregnancy can affect her children, see Maternal Diet May Affect Stress Responses in Children and Animal Protein, Pregnancy, and Childhood Obesity.

Protein is such a misunderstood nutrient. For more information, check out:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

What Not to Do When You Handle Receipts

The plastics chemical bisphenol A, commonly known as BPA, was banned for use in baby bottles in Canada in 2008, in France in 2010, in the European Union in 2011, and in the United States in 2012. Then, in 2015, France forbade the use of BPA in any food or beverage packaging, something the U.S. Food and Drug Administration had decided was not warranted. But, what about the more than 90 studies “reporting relationships between total BPA in [people’s] urine and a wide array of adverse health outcomes, including a significant increase in the likelihood of developing cardiovascular disease and type 2 diabetes, obesity, impaired liver function, impaired immune and kidney function, inflammation, reproductive effects in women…[and] in men…, altered thyroid hormone concentrations, and neurobehavioral deficits such as aggressiveness, hyperactivity, and impaired learning”?

Only a very small minority of studies appear to support the U.S. government’s assertions that there were no effects of BPA at low doses. Where is the disconnect? Governmental regulatory agencies determine safety levels of chemicals by sticking tubes down into the stomachs of lab animals. In these types of tests, BPA is released directly into the stomach, where it goes to the liver to be detoxified into an inactive form called BPA-glucuronide. So, very little active BPA gets into the bloodstream. But, that’s not what studies on humans show. People have active BPA in their blood. How did the FDA respond? By rejecting all such human studies as implausible.

The problem with a “blanket rejection” of human data is that there may be sources of BPA exposure that are not modeled by stomach tube exposure in rats. After all, “[t]his isn’t how food actually enters our bodies. We chew it, move it around in our mouths…before it enters the stomach.” It turns out “that BPA can be completely absorbed directly into the bloodstream from the mouth,” thus bypassing instant liver detoxification. The same would be the case for BPA absorbed through the skin, which you can see at 2:08 in my video BPA on Receipts: Getting Under Our Skin.

Thermal paper, often used for cash register receipts, luggage tags, and many bus, train, and lottery tickets, is 1 to 2 percent BPA by weight. Taking hold of a receipt can transfer BPA to our fingers, especially if they’re wet or greasy. Does the BPA then get absorbed into our system through the skin? Cashiers were found to have more BPA flowing through their bodies “[c]ompared with other occupations,” but that was based on only 17 people. “Strict vegetarians had lower urinary BPA concentrations compared with nonvegetarians,” but, once again, the sample size was too small to really make a conclusion. It’s been estimated that even cashiers handling receipts all day may not exceed the “tolerable daily intake” of BPA—however, that could change if they were using something like hand cream.

Indeed, “many skin-care products, including hand sanitizers, lotions, soaps and sunscreens,” contain chemicals that enhance skin penetration. So, using a hand sanitizer, for example, before touching a receipt could cause a breakdown of the skin barrier.

What’s more, we now know that “using hand sanitizer and handling a thermal receipt…prior to picking up and eating food with [our] hands” results in high blood levels of active BPA. Researchers at the University of Missouri, conducting a study to mimic aspects of the behavior of people in a fast-food restaurant found that when people handled a receipt right after using the hand sanitizer Purell, BPA was transferred to their fingers. Then, BPA was transferred from their fingers to their fries, and the combination of absorption through the skin and mouth led to significant levels of active BPA in their blood, as you can see at 3:45 in my video.

We can hold a receipt in our hand for 60 seconds and only come away with 3 micrograms of BPA in our body. In contrast, if we pre-wet our hands with hand sanitizer, we can get 300 micrograms in just a few seconds—a hundred times more BPA, as you can see at 4:05 in my video. “These findings show that a very large amount of BPA is transferred from thermal paper to a hand as a result of holding a thermal receipt for only a few seconds immediately after using a product with dermal penetration enhancing chemicals,” like hand lotion. This could explain why dozens of human studies show active BPA in people’s systems, contrary to the assumptions based on stomach tube studies in rodents.

When actual evidence contradicts your assumptions, you reject your assumptions. The FDA, however, rejected the evidence instead.


Watch my video to learn Why BPA Hasn’t Been Banned.

For more on BPA, see:

Interested in other examples of Food and Drug Administration failings? Check out:

Phthalates are another class of concerning plastics compounds. For more, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Treating Prostate Cancer with Green Tea

Green tea has been called nature’s defense against cancer. Population studies linking green tea consumption with lower cancer risk have led some to advocate for the incorporation of green tea into the diet “so as to fully benefit from its anticarcinogenic properties.” What, after all, is the downside?

But, population studies can’t prove cause and effect. Indeed, “it is not possible to determine from these population-based studies whether green tea actually prevents cancer in people”…until it is put to the test.

Prostate cancer is preceded by a precancerous condition known as intraepithelial neoplasia. You can see a graphic of the progression at 0:41 in my video Treating Prostate Cancer with Green Tea. Within one year, about 30 percent of such lesions turn into cancer. Because no treatment is given to patients until cancer is diagnosed, this presents a perfect opportunity to try green tea. In the study, 60 men with precancerous prostate intraepithelial neoplasia were randomized into either a green tea group or a placebo group. Since it’s hard to make a convincing placebo tea, the researchers used green tea pills that were roughly equivalent to about six cups of green tea a day and compared them to sugar pills. Six months into the study, they took biopsies from everyone. In the placebo group, 6 of the 30 men developed cancer by the halfway point and 3 of the remaining 24 developed it by the end of the year. So, 9 out of 30 in the placebo group, about 30 percent, developed cancer within the first year, which is what normally happens without any treatment. In the green tea group, however, none of the 30 men developed cancer within the first six months and only one developed it by the end of the year. Only 1 out of 30 is nearly ten times less than the placebo group. This marked the first demonstration that green tea compounds could be “very effective for treating premalignant lesions before [prostate cancer] develops.” Even a year later, after the subjects stopped the green tea, nearly 90 percent of the original green tea group remained cancer-free, while more than half of the placebo group developed cancer, as you can see at 2:09 in my video. This suggests that the benefits of the green tea may be “long-lasting,” with an overall nearly 80 percent reduction in prostate cancer.

What if you already have prostate cancer? A proprietary green tea extract supplement was given to 26 men with confirmed prostate cancer for an average of about a month before they had their prostates removed, and there was a significant reduction in a number of cancer biomarkers such as PSA levels, suggesting a shrinkage of the tumor. However, there was no control group, and the study was funded by the supplement company itself. When an independent group of researchers tried to replicate the results in a randomized, double-blind, placebo-controlled trial, they failed to find any statistically significant improvement. Perhaps green tea is only effective in the precancerous state and not powerful enough “to meaningfully impact overt prostate cancer”?

It certainly didn’t seem to help for advanced metastatic cancer in the two studies that tried it. What’s more, doubt has recently been cast on the precancerous results. When researchers tried to replicate it, the green tea extract group only seemed to cut prostate cancer development about in half, which very well may have happened just by chance, given the small number of people in the study. So where does that leave us?

Unfortunately, green tea extract pills are not without risk. There have been about a dozen case reports of liver damage associated with their use. Until there’s more solid evidence of benefit, I’d stick with just drinking the tea. Green or black? A recent study that randomized about a hundred men with prostate cancer to consume six cups a day of green tea or black tea found a significant drop in PSA levels and NF-kB in the green tea group, but not in either the black tea or control groups, as you can see at 4:12 in my video. NF-kB is thought to be a prognostic marker for prostate cancer progression, so the green tea did appear to work better than the black tea.


What happens if we pack our diet with all sorts of plant foods? See my Cancer Reversal Through Diet? video.

Before and after: Learn about Preventing Prostate Cancer with Green Tea and Changing a Man’s Diet After a Prostate Cancer Diagnosis.

Similar studies were done with pomegranates. I discuss the results in Pomegranate vs. Placebo for Prostate Cancer.

Interested in other ways to prevent or treat prostate cancer? See:

What about green tea and other types of cancer? Check out:

For more on some of green tea’s other benefits, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations: