"The Effect of Animal Protein on Stress Hormones, Testosterone, and Pregnancy"
High-protein diets during pregnancy: healthful or harmful?
A question answered about 40 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 diets of the poor.
Had they 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 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 6 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 the 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 crab meat, tuna fish, cottage cheese
and the stress hormone levels shoot 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 can chronically stimulate your stress response axis
and increase the release of vasoactive hormones
that 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 whites,
and switch them to a high-carb diet of bread, vegetables, fruit,
and sugary junk, their cortisol levels drop about a quarter within 10 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— you gain 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 the 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 fetuses, 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 30 years later,
though green vegetable consumption was found to be protective.
Higher meat and fish consumption, like 3 servings a day compared to 1 or 2,
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 2 servings of meat per day,
versus about 2 a day, versus about 2 to 3 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 response 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.