The Effect of Animal Protein on Stress Hormones, Testosterone, and Pregnancy

Michael Greger M.D. FACLM · January 18, 2017 · Volume 34

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What happened to women who were randomized to eat more meat and dairy during pregnancy? What effect does animal protein consumption have on cortisol and testosterone levels in men?

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Transcript

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.

“High-protein diets during pregnancy: healthful or harmful?” A question answered about forty years ago, in the infamous Harlem Trial of 1976: a “randomized controlled trial of nutritional supplementation in pregnancy, in a poor black urban population.” The “study…was begun at a time when protein was [just] assumed to be deficient in the diet[s] of the poor…” Had they actually analyzed their diets before they started, they would have realized that wasn’t true. But, why let facts get in the way of assumptions?

So, they split poor black pregnant women into three groups, and gave them an extra 40 grams of animal protein a day—basically a couple cans of Ensure, versus about six extra grams of animal protein, or no extra protein, and sat back, and watched what happened. The high-protein group suffered “an excess of very early premature births and associated [infant] deaths,” as well as “significant growth retardation” in the babies that survived. More protein meant more prematurity, more deaths, and more growth retardation.

And, when kids grow up, 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 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 talked about before, or the animal protein-induced rise in the growth hormone IGF-1. Or, it could be due to a steroid stress hormone, called cortisol.

A single meal high in animal protein can nearly double the level of stress hormone in the blood within a half hour of consumption—much more than a meal closer to the recommended level of protein. Give someone a meal of crabmeat, tuna fish, cottage cheese, and the stress hormone levels shoots up. But, instead, give someone some barley soup, and a vegetable stir-fry on rice, and the stress hormone level goes down after the meal.

And, imagine if you did the meat, fish, dairy meal-after-meal, day-after-day. You could chronically stimulate your stress response axis, and increase the release of vasoactive hormones that can increase your blood pressure. And, all that extra cortisol release has been linked to increased risk for elevated blood levels of insulin, triglycerides, and cholesterol.

If you take men on a high-protein diet—”meat, fish, poultry, egg white[s]”—and switch them to a high-carb diet of “bread, vegetables, fruit, and [sugary junk,]” their cortisol levels drop about a quarter within ten days. At the same time, their testosterone levels shoot up by about the same amount. High-protein diets suppress testosterone. That’s why if you take men eating plant-based diets, and have them start eating meat every day, their testosterone levels go down, and actually some estrogens go up.

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, 75% drop in testosterone levels in the months leading up to a competition. Testosterone levels cut by more than half; enough to drop a guy into an abnormally low range. It’s ironic that they’re eating protein to look manly on the outside, but it makes 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—gaining body fat.

What does cortisol have to do with weight? Well, there’s actually a disease caused by having too much cortisol, called Cushing’s syndrome. And, this is kind of a before-and-after in terms of abdominal obesity, which is most of that white. Even in normal women, though, chronic stress—chronic high cortisol levels—can contribute to obesity. And, if they’re pregnant, high-meat, low-carb diets may increase cortisol levels in the mom—which can lead to inappropriate fetal exposure to cortisol, which, in turn, can affect the developing fetus, resetting their whole stress-response thermostat, leading to higher cortisol levels their whole life, which can have serious health consequences that can stick with them their whole lives.

And indeed, that’s what they found. Every maternal daily portion of meat and fish was associated with 5% higher cortisol levels in their children as much as thirty years later—though green vegetable consumption was found to be protective. Higher meat and fish consumption—like 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.

And, the adult children of mothers who ate a lot of meat during pregnancy don’t just walk around with higher stress hormone levels, but also appear to react more negatively to whatever life throws at them. If you put them through the Trier Test—which involves public speaking in front of a panel of judges, followed by a live math exercise, here’s the stress hormone responses in those moms who ate less than two servings of meat per day, versus about two a day, versus about two to three servings a day. Note before the test started, the two lower-mother meat groups started out about the same, just walking around, but their exaggerated cortisol responses was laid bare when exposed to a stressful situation.

Now, the real-world effects of this is that after that sort of test, if you give people their own private snack buffet, with fruits and veggies versus fatty, sugary, comfort foods like chocolate cake, guess who eats less fruits and veggies? Those who have these high chronic stress levels. Cortisol has been implicated as a factor in motivating food intake, even when you’re not really hungry.

So, no surprise that animal protein intake during pregnancy may lead to larger weight gain for her children later in life, and maybe even her grandchildren. That’s how much the stress axis can get mucked around. Recent evidence suggests that the long-term adverse consequences “may not be limited to one generation;…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].”

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Image credit: Carolyn Sewell via flickr. Image has been modified.

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.

“High-protein diets during pregnancy: healthful or harmful?” A question answered about forty years ago, in the infamous Harlem Trial of 1976: a “randomized controlled trial of nutritional supplementation in pregnancy, in a poor black urban population.” The “study…was begun at a time when protein was [just] assumed to be deficient in the diet[s] of the poor…” Had they actually analyzed their diets before they started, they would have realized that wasn’t true. But, why let facts get in the way of assumptions?

So, they split poor black pregnant women into three groups, and gave them an extra 40 grams of animal protein a day—basically a couple cans of Ensure, versus about six extra grams of animal protein, or no extra protein, and sat back, and watched what happened. The high-protein group suffered “an excess of very early premature births and associated [infant] deaths,” as well as “significant growth retardation” in the babies that survived. More protein meant more prematurity, more deaths, and more growth retardation.

And, when kids grow up, 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 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 talked about before, or the animal protein-induced rise in the growth hormone IGF-1. Or, it could be due to a steroid stress hormone, called cortisol.

A single meal high in animal protein can nearly double the level of stress hormone in the blood within a half hour of consumption—much more than a meal closer to the recommended level of protein. Give someone a meal of crabmeat, tuna fish, cottage cheese, and the stress hormone levels shoots up. But, instead, give someone some barley soup, and a vegetable stir-fry on rice, and the stress hormone level goes down after the meal.

And, imagine if you did the meat, fish, dairy meal-after-meal, day-after-day. You could chronically stimulate your stress response axis, and increase the release of vasoactive hormones that can increase your blood pressure. And, all that extra cortisol release has been linked to increased risk for elevated blood levels of insulin, triglycerides, and cholesterol.

If you take men on a high-protein diet—”meat, fish, poultry, egg white[s]”—and switch them to a high-carb diet of “bread, vegetables, fruit, and [sugary junk,]” their cortisol levels drop about a quarter within ten days. At the same time, their testosterone levels shoot up by about the same amount. High-protein diets suppress testosterone. That’s why if you take men eating plant-based diets, and have them start eating meat every day, their testosterone levels go down, and actually some estrogens go up.

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, 75% drop in testosterone levels in the months leading up to a competition. Testosterone levels cut by more than half; enough to drop a guy into an abnormally low range. It’s ironic that they’re eating protein to look manly on the outside, but it makes 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—gaining body fat.

What does cortisol have to do with weight? Well, there’s actually a disease caused by having too much cortisol, called Cushing’s syndrome. And, this is kind of a before-and-after in terms of abdominal obesity, which is most of that white. Even in normal women, though, chronic stress—chronic high cortisol levels—can contribute to obesity. And, if they’re pregnant, high-meat, low-carb diets may increase cortisol levels in the mom—which can lead to inappropriate fetal exposure to cortisol, which, in turn, can affect the developing fetus, resetting their whole stress-response thermostat, leading to higher cortisol levels their whole life, which can have serious health consequences that can stick with them their whole lives.

And indeed, that’s what they found. Every maternal daily portion of meat and fish was associated with 5% higher cortisol levels in their children as much as thirty years later—though green vegetable consumption was found to be protective. Higher meat and fish consumption—like 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.

And, the adult children of mothers who ate a lot of meat during pregnancy don’t just walk around with higher stress hormone levels, but also appear to react more negatively to whatever life throws at them. If you put them through the Trier Test—which involves public speaking in front of a panel of judges, followed by a live math exercise, here’s the stress hormone responses in those moms who ate less than two servings of meat per day, versus about two a day, versus about two to three servings a day. Note before the test started, the two lower-mother meat groups started out about the same, just walking around, but their exaggerated cortisol responses was laid bare when exposed to a stressful situation.

Now, the real-world effects of this is that after that sort of test, if you give people their own private snack buffet, with fruits and veggies versus fatty, sugary, comfort foods like chocolate cake, guess who eats less fruits and veggies? Those who have these high chronic stress levels. Cortisol has been implicated as a factor in motivating food intake, even when you’re not really hungry.

So, no surprise that animal protein intake during pregnancy may lead to larger weight gain for her children later in life, and maybe even her grandchildren. That’s how much the stress axis can get mucked around. Recent evidence suggests that the long-term adverse consequences “may not be limited to one generation;…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].”

Please consider volunteering to help out on the site.

Image credit: Carolyn Sewell via flickr. Image has been modified.

Doctor's Note

There was a lot to unpack in that video, which seemed more like five videos in one. Rather than break it up, since so much of it was tied together, as you could see, I produced this one, heftier video. You may want to watch it a second time 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:

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