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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:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

30 responses to “What Happens When Pregnant Women Eat More Animal Protein

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      1. Barb,

        Thanks for posting that.

        Dr. Lustig showed where stress has one mechanism that led to Metabolic syndrome.

        The culture is so confusing and so stressful and the experts are so polarized and so manipulative that it is so hard to know who to trust.

        The concept that I fixed my animal products and lowered my sugar considerably but got so few results without fixing my circadian rhythms, my Vitamin D and sleep and stress.

        Most of the people I am interacting with could never possibly succeed at this process and just don’t even have the time that I have been able to put into it these past 2-1/4 years. I have so many jobs I can do where I can watch videos at the same time. People who don’t learn this when they are young don’t even have a chance at succeeding.

        Dr. Lustig was talking to professionals about how you can’t fix it if you don’t know what is causing problems.

        There are sooooooo many things that you have to fix and it is all intentionally confusing.

        Anyway, I have crossed so many things off the list and I still am not sure I will lose very much weight. I did have a drop when I started Vitamin D and started getting sleep. Stress will be the next one, but I have noticed that I am craving hummus – which tells me that I am craving fats and I am confused about what to eat still.

        Getting there though and I think my level of scientific understanding has increased the past few weeks.

        But I gained back a few pounds eating too much hummus out of hunger again and started craving 5-bean casserole which is probably craving brown sugar, so metabolic syndrome is probably still there.

        1. Great post. I have been eating veryu much towards the WFPB – SOS for quite a while now. My LDL levels are high which was a bit of a surprise for me. Will also be working more on sleep patterns and more exercise. I may have to get more ruthless about oils – I get some if I’m out and about (e.g. a hummus wrap for lunch) or if my husband cooks.

  1. Dr. Gregor,

    You may have interest in Dose dependent toxicity of glutamic acid: A review. (Samuels A. (2020) Dose dependent toxicity of glutamic acid: a review, International Journal of Food Properties, 23:1, 412-419, DOI: 10.1080/10942912.2020.1733016.

    Data confirm that manufactured free glutamate, such as that found in MSG, when ingested in quantity by pregnant women, is passed to neonates (whose brains are vulnerable/immature/easily damaged) where it kills brain cells.

  2. Please take up the subject of “plant-based” protein substitutes. Consumers seem to be unaware that there are no plants (things that grow in the ground) in them. They are basically chemicals of low nutritional value with flavor-enhancers like MSG, autolyzed yeast, and hydrolyzed proteins added to make up for the flavor that made-in-the-plant-chemicals don’t have.

    1. Hi Adrienne, Dr. Greger actually has some plant-based “meat” videos coming out in the next few months. Be sure you’re subscribed to the video feed so you see them when they first come out!

  3. Anyway, I am not giving up and I am going to celebrate that I am not craving cheese and candy bars or fried foods and ice cream.

    It just is so hard for me to figure this out.

    There are so many factors and I look at my salad and upping the vinegar and lowering the dressing didn’t cause more weight loss. It caused hummus and 5-bean casserole cravings.

    I think I come here because it would be so easy to give up, but I am not giving up.

      1. Just my luck… when shopping this morning I felt I had to make a decision between a sack of oranges and a sack of grapefruit… I chose the grapefruit. ‘-(

        1. Lonnie,

          That is a really cool article.

          I love oranges. I eat an orange just about every day.

          I am sure grapefruit have something just as special, but there are always 4 kinds of organic oranges and some are usually on sale.

          Tonight, I shifted gear and went shopping and bought Lima beans and edamame.

          Along with packs of greens and cruciferous. It is what I eat almost daily anyway, but the Lima beans are going to be cooked hot.

          Seeing if I can mix things up a little.

          I know that I need even maybe to find a different community.

          But I know that there aren’t passionate communities online.

          You have to live near people who are doing it.

  4. I am sure grapefruit have something just as special
    Yeah, I think the nobiletin is found in just about all citrus… just not as much as in the tangerine or orange.

    But I think the grapefruit might yield what it has by peeling the orb and eating the sections with membrane intact. Also thinking about freeze drying the peels and grinding them into powder to add to food.

    Tried to find the nobiletin as a supplement but no luck.

  5. Wit apologies to Reality Bites, bless his little cotton socks, here is another off-topic post’

    I came across this update from Veganhealth earlier and think that it is worth sharing:

    Vegan Health Updates
    We updated our Vitamin B12: Vegan Sources page with two intervention studies using vitamin B12-fortified toothpaste.

    B12 Toothpaste in Vegans
    A 2017 randomized, double-blind, placebo-controlled trial was the first to test the efficacy of vitamin B12-fortified toothpaste in raising blood markers of vitamin B12 status (1). The trial was conducted in Germany and included 66 vegans. 22 participants in the placebo group and 31 in the intervention group were taking B12 supplements; they were asked to continue their supplementation behavior throughout the study).

    Participants were instructed to use the study-issued toothpaste twice a day, brushing for two minutes each time. The treatment toothpaste contained 100 mcg B12/g toothpaste. Researchers estimated participants received 130-290 mcg B12 per day via the toothpaste, but were not able to calculate or measure how much B12 the participants absorbed.

    At the end of 12 weeks, compared to their baseline values, participants in the intervention group experienced significantly increased B12 (from 197±137 to 279±134 pmol/L; p=0.001) and holotranscobalamin (from 35±35 to 64±34 pmol/L; p<0.001), significantly decreased methylmalonic acid (MMA) (from 0.303±0.361 to 0.212±0.123 µmol/L; p=0.001), and not-quite-significantly decreased total homocysteine (from 10.6±6.2 to 9.7±6.4 µmol/L; p=0.058). These changes are associated with improved B12 status.

    Changes were greater in those reporting not taking B12 supplements. Participants in the placebo group did not experience significant changes in their B12 markers between baseline and the end of the intervention.

    Based on this study, it appears that B12-fortified toothpaste may serve as a viable source of vitamin B12 for vegans.

    B12 Toothpaste in Older Adults
    A 2019 randomized, double-blind, placebo-controlled trial assessed the efficacy of vitamin B12-fortified toothpaste in a sample of 92 older adults (2). After 3 months, those receiving the treatment toothpaste (100 mcg B12/g toothpaste) experienced significantly greater B12 levels (368 vs. 295 pmol/L; p = 0.005) compared with the placebo group. Researchers concluded that B12-fortified toothpaste may be used to help prevent vitamin B12 depletion in older people.

    1. Siebert AK, Obeid R, Weder S, Awwad HM, Sputtek A, Geisel J, Keller M. Vitamin B-12-fortified toothpaste improves vitamin status in vegans: a 12-wk randomized placebo-controlled study. Am J Clin Nutr. 2017 Mar;105(3):618-625. doi: 10.3945/ajcn.116.141978. Epub 2017 Jan 4.

    2. Zant A, Awwad HM, Geisel J, Keller M, Obeid R. Vitamin B12-fortified toothpaste improves vitamin status in elderly people: a randomized, double-blind, placebo-controlled study. Aging Clin Exp Res. 2019 Dec;31(12):1817-1825. doi: 10.1007/s40520-019-01125-6. Epub 2019 Jan 24.

    Omega-3s Updated
    Feb 18, 2020 11:21 am

    We’ve made three updates to the Omega-3s Part 2—Research page.

    First, a 2019 randomized controlled trial challenged the idea that EPA is commonly created from DHA (1). Study participants ingested DHA with labeled carbon and researchers did not find the labeled carbon in the participants’ EPA. They concluded that the increase in EPA levels after DHA ingestion is not from retroconversion, but rather from “slowed metabolism and/or accumulation of plasma EPA.”

    Second, a 2020 meta-analysis of six cohort studies found no correlation between eating fish and a reduced risk of cardiovascular disease or mortality (2). This further strengthens our conclusion that plant eaters do not need to supplement with EPA and DHA to match the EPA and DHA intakes of fish eaters for the purpose of cardiovascular health. In fact, vegetarians tend to have a significantly reduced risk of heart disease already.

    Third, a 2019 systematic review and meta-analysis of 13 randomized controlled trials concluded that marine-derived omega-3 supplementation is associated with a reduced risk of heart disease (3). The following points are important to consider:

    The meta-analysis is, for the most part, using pharmacological doses of omega-3 and therefore isn’t pertinent to diet.
    Such doses appear to work in regards to reducing triglycerides; if you’re a vegan with high triglycerides, you may consider talking to your doctor about pharmacological doses of omega-3s, for which there are vegan versions.
    Fish-eaters are thought to achieve health benefits from about 250 mg EPA and DHA per day and this can easily be obtained through supplementation, though we don’t think there is enough evidence to suggest vegans who do not supplement are at an increased risk of CVD.
    These studies do not change our omega-3 recommendations.

    1. Metherel AH, Irfan M, Klingel SL, Mutch DM, Bazinet RP. Compound-specific isotope analysis reveals no retroconversion of DHA to EPA but substantial conversion of EPA to DHA following supplementation: a randomized control trial. Am J Clin Nutr. 2019 Oct 1;110(4):823-831.

    2. Zhong VW, Van Horn L, Greenland P, Carnethon MR, Ning H, Wilkins JT, Lloyd-Jones DM, Allen NB. Associations of Processed Meat, Unprocessed Red Meat, Poultry, or Fish Intake With Incident Cardiovascular Disease and All-Cause Mortality. JAMA Intern Med. 2020 Feb 3. doi: 10.1001/jamainternmed.2019.6969. [Epub ahead of print]

    3. Hu Y, Hu F, Manson JE. Marine Omega-3 Supplementation and Cardiovascular Disease: An Updated Meta-Analysis of 13 Randomized Controlled Trials Involving 127 477 Participants. J Am Heart Assoc. 2019 Oct;8(19):e013543.

    1. YR,

      I thought of you today.

      The radio was doing news bits like every touch screen at McDonalds had traces of feces on it.

      That sounded like one you would post.

      Hint: more and more places try to get you to not have cashiers.

      Home Depot, grocery stores, places like CVS where sick people just said “Yes” on the exact same spot on the Credit card screen, etc.

      Not to mention that we touch those screens and come back and touch our cell phones.

      I did end up getting the Wabi Baby at Amazon after all. Turns out they had a gift card on my account that covered most of it.

      It is starting to spread here now.

      Elderly people are the ones who are at risk.

      Washing machines not cleaning clothes and Dawn not disinfecting things like sinks and Lysol not disinfecting well and Norwex not disinfecting and most steam cleaners not being hot enough is what comes to mind.

  6. The doctors that I have been following for coronavirus said that today’s news in South Korea was that 60% of the cases are now being spread through the community, rather than people knowing where they got it.

    They also said that America – the CDC has totally dropped the ball and that where other small countries have tested 200,000 people, America has only tested hundreds of people and that we might have been having cases for weeks.

  7. They also said things like India, who manufactures a lot of the generic antibiotics is not going to be exporting 26 types of antibiotics so they can be prepared for their own people, so we might find that we are short in antibiotics during this.

  8. I am very disappointed with this video and article. People trust you to evaluate studies properly and give the factual results.

    You’re using studies such as the one on low income African Americans and saying the extra protein caused problems. How about the 310 calories in the drink that did not come from protein, which were probably about 77 grams of sugar each day? There are too many variables but you’re blaming the animal protein….

    Or the two studies on a single bodybuilder, yes an N of 1 in each of the two studies you referenced. It is a poor selection of (case) studies just based on that alone. However, in both cases the subject had a hypocaloric diet, which is what actually likely accounted for the decrease in testosterone, just like the heart rate decreased, the blood pressure decreased and body fat decreased. How come you’re not giving “high animal protein” credit for those (beneficial) results too?

    This is a disgrace. I don’t even want to open the rest of the studies. I don’t know if you’re actually doing the work or have employees doing the work now, but I can’t trust your information any more. I am honestly saddened.

    Regards, Michael

  9. In the video you discuss the effects of animal protein on testosterone levels, do plant-based proteins have the same effect?

  10. Hi, I’m a brazilian nutritionist/dietitian and I have a question about what the article says (1st I’m sorry for my English, I taught myself and I have some flaws): the article encourages not-to-eat/reduces animal protein, but we know the vegetable protein has low absorption. How we are going to offer protein to people?

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