Meat Can Cause Stress Hormone Levels to Rise and Testosterone levels to Drop

A critique of the scientific validity of the dietary advice in Men’s Health magazine discovered nuggets claiming meat can give men “a testosterone boost,” but we’ve known for a quarter century that a meal with that much fat can drop testosterone levels by nearly one-third within hours. In fact, a significant drop of both free and bound testosterone in the bloodstream occurs within just one hour of it going in one’s mouth, whereas a low-fat meal of mostly carbs has no such effect. Based on in vitro studies on the effects of fat on testicle cells in a petri dish, researchers suspect fat in the blood may actually suppress testosterone production in real time. If you feed people lots of eggs and meat, including fish and poultry, and then switch them to a diet with bread, fruit, vegetables, and sugar—but about the same amount of fat—all their testosterone levels go up. Even more importantly, however, all their levels of cortisol, a stress hormone produced by our adrenal glands, go down.

Having low stress hormone levels is good, because high cortisol levels may “strongly predict cardiovascular death” in men and women both with and without pre-existing cardiovascular disease. In fact, this may help explain “death from a broken heart,” the heightened heart attack and stroke risk in the immediate weeks following the loss of a spouse. Higher cortisol levels days, months, or even years after losing someone you love may increase cardiac risk and reduce immune function. And, the rise in stress hormone levels from the loss of a spouse, a bump of about 50 points, is less than the bump you get by eating high-meat diet.

Cortisol may also help explain why those who are depressed tend to put on abdominal fat. The reason obesity around the middle is associated with elevated cortisol secretion may be that abdominal fat kind of sucks it up, so the accumulation of fat around our internal organs may be an adaptation by which our body deals with excess stress.

These spikes in stress hormone levels every time we eat a lot of meat may not just affect our health, but that of our children, which I discuss in my video Maternal Diet May Affect Stress Responses in Children. “Substantial evidence now suggests that maternal diets of high protein density have adverse effects on the fetus.” For example, back in the 1960s, an experiment was performed on pregnant women in Motherwell, Scotland, in which they were told to eat a high-meat diet in hopes of preventing preeclampsia, a disease of pregnancy. It didn’t work. In fact, the lowest preeclampsia rates I’ve ever seen were among women eating strictly plant-based diets—only 1 case out of 775 pregnancies. Preeclampsia normally strikes about 5 percent of pregnancies, so there should have been dozens of cases, suggesting a plant-based diet could alleviate most, if not all, of the signs and symptoms of this potentially serious condition. So what did happen when pregnant women went from eating about one daily portion of meat to about two portions a day? Mothers who ate more meat and fewer vegetables during pregnancy gave birth to children who grew up to have higher blood pressures.

“One explanation proposed for the adverse effects of high-meat/fish consumption is that this may increase maternal cortisol concentrations, which, in turn, affect the developing fetus,” resetting his or her stress hormone thermostat to a higher level. But, we don’t know until we put it to the test. And indeed, researchers found higher blood cortisol levels “in both the sons and daughters of women who had reported higher meat/fish” consumption, about a 5 percent increase for every meat serving per day. Such diets may present a metabolic stress to the mother and kind of reprogram the adrenal axis of their children, leading to lifelong hypercortisolemia, elevated levels of stress hormones in the blood. This may help explain why every daily portion of meat during late pregnancy may lead to a 1 percent greater fat mass in their children by the time they reach adolescence. So, this could increase the risk of their children becoming obese later in life and thus has “important implications for public health and in terms of prevention of obesity.”

What if they’re already born? We may be able to bring down children’s stress hormone levels with similar dietary changes, but this is just baseline stress hormone levels. Do children of mothers who eat more meat during pregnancy also have exaggerated responses to life stressors? Researchers put them through a stressful challenge—public speaking and mental arithmetic—and then measured their cortisol responses. If their mom ate less than two servings of meat/fish a day while she was carrying them, they got little shots of stress hormones from their adrenal glands. Those whose moms ate more really got stressed out, and those whose moms ate the most—17 or more servings a week, which is more than 2 servings each day—appeared to be really quaking in their boots. In a way, you are what your mother ate.


Want more craziness from Men’s Health magazine? Check out my video Changing a Man’s Diet After a Prostate Cancer Diagnosis.

Here are some other popular videos about eating healthfully during pregnancy:

In health,
Michael Greger, M.D.

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

How Much Vinegar Every Day?

Consuming vinegar with a meal reduces the spike in blood sugar, insulin, and triglycerides, and it appears to work particularly well in those who are insulin resistant and on their way to type 2 diabetes. No wonder the consumption of vinegar with meals was used as a folk medicine for the treatment of diabetes before diabetes drugs were invented.

Many cultures have taken advantage of this fact by mixing vinegar with high glycemic foods. For example, in Japan, they use vinegar in rice to make sushi, and, in the Mediterranean, they dip bread into balsamic vinegar. Throughout Europe, a variety of sourdough breads can lower both blood sugar and insulin spikes. You can get the same effect by adding vinegar to boiled white potatoes then cooling them to make potato salad.

Adding vinegar to white bread doesn’t just lower blood sugar and insulin responses—it increases satiety, or the feeling of being full after a meal. As you can see in my video Optimal Vinegar Dose, a study found that if you eat three slices of white bread, it may fill you up a little, but in less than two hours, you’re hungrier than when you began eating. If you eat that same amount of bread with some vinegar, though, you feel twice as full and, even two hours later, still feel nearly just as full as if you had just eaten the three pieces of bread plain. But this remarkable increase and prolongation of satiety took nearly two tablespoons of vinegar. That’s a lot of vinegar. What’s the minimum amount?

It turns out that even just two teaspoons of vinegar with a meal can significantly decrease the blood sugar spike of a refined carb meal, a bagel and juice, for instance. You could easily add two teaspoons of vinaigrette to a little side salad or two teaspoons of vinegar to some tea with lemon. Or even better you could scrap the bagel with juice and just have some oatmeal with berries instead.

What if you consume vinegar every day for months? Researchers at Arizona State University randomized pre-diabetics to take daily either a bottle of an apple cider vinegar drink—a half bottle at lunch, and the remaining half at dinner—or an apple cider vinegar tablet, which was pretty much considered to be a placebo control: While the bottled drink contained two tablespoons of vinegar, the two tablets only contained about one third of a teaspoon. So in effect, the study was comparing about 40 spoonfuls of vinegar a week to 2 spoonfuls for 12 weeks.

What happened? On the vinegar drink, fasting blood sugars dropped by 16 points within one week. How significant is a drop of 16 points? Well this simple dietary tweak of a tablespoon of vinegar twice a day worked better than the leading drugs like Glucophage and Avandia. “This effect of vinegar is particularly noteworthy when comparing the cost, access, and toxicities” associated with pharmaceutical medications. So the vinegar is safer, cheaper, and more effective. This could explain why it’s been used medicinally since antiquity. Interestingly, even the tiny amount of vinegar in pill form seemed to help a bit. That’s astonishing. And, no: The study was not funded by a vinegar company.

What about long-term vinegar use in those with full-blown diabetes? To investigate this, researchers randomized subjects into one of three groups. One group took two tablespoons of vinegar twice a day, with lunch and supper. Another group ate two dill pickles a day, which each contained about a half tablespoon’s worth of vinegar. A third group took one vinegar pill twice a day, each containing only one sixteenth of a teaspoon’s worth of vinegar. I wasn’t surprised that the small dose in the pill didn’t work, but neither did the pickles. Maybe one tablespoon a day isn’t enough for diabetics? Regardless, the  vinegar did work. This was all the more impressive because the diabetics were mostly well controlled on medication and still saw an additional benefit from the vinegar.


Make sure to check out my other videos on vinegar’s benefits:

This vinegar effect seems a little too good to be true. There have to be some downsides, right? I cover the caveats in Vinegar Mechanisms and Side Effects.

There are a few other foods found to improve blood sugar levels:

The best approach, of course, is a diet full of healthy foods:

In health,
Michael Greger, M.D.

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

Were We Wrong About Fiber?

In my video Is the Fiber Theory Wrong?, I present that fiber-containing foods may not only help prevent heart disease, but also help treat it as well. Heart patients who increase their intake of fiber after their first heart attack reduce their risk of a second and live longer than those who don’t. But what if we don’t want to have a heart attack in the first place? If 7 grams of fiber gets us a 9 percent reduced risk, would 77 grams a day drop our risk by 99 percent? That’s about how much fiber they used to eat in Uganda, a country in which coronary heart disease, our number-one killer, was almost nonexistent.

Heart disease was so rare among those eating traditional plant-based diets in Uganda that papers were published with such titles as “A Case of Coronary Heart Disease in an African.” After 26 years of medical practice in East Africa, doctors finally recorded their first case of coronary heart disease (in a judge who consumed a “partially Westernized diet,” in which fiber-free foods, such as meat, dairy, and eggs, displaced some of the plant foods in the traditional diet).

Were there so few cases because Africans just didn’t live very long? No, the overall life expectancy was low because of diseases of childhood, such as infections, but, when Africans reached middle age, they had the best survival rates, thanks in part to our number-one killer being virtually absent. Of course, since diets have been Westernized across the continent, coronary heart disease is now their number-one killer as well, going from virtually nonexistent to an epidemic.

Some blame this change on too much animal fat, while others blame it on too little fiber, but they both point to the same solution: a diet centered on unrefined plant foods. In fact, sometimes, it’s easier to convince patients to improve their diets by eating more of the good foods to crowd out some of the less healthful options.

The “dietary fiber hypothesis,” first proposed in the 1970s, zeroed in on fiber as the dietary component that was so protective against chronic disease. Since then, evidence has certainly accumulated that those who eat lots of fiber appear to be protected from several chronic conditions. But maybe fiber is just a marker for the consumption of foods as grown, whole, unprocessed plant foods, the only major source of fiber. Maybe all these studies showing fiber is good are just showing that eating lots of unrefined plant foods is good. “Fiber is but one component of plant food, and to neglect the other components [such as all the phytonutrients] is to seriously limit our understanding.”

Why did Drs. Burkitt, Trowell, Painter, and Walker—the fathers of the fiber theory—place all their bets on fiber? One possible explanation is that they were doctors, and we doctors like to think in terms of magic bullets. That’s how we’re trained: there’s one pill, one operation. They were clinicians, not nutritionists, and so they developed a reductionist approach. The problem with that approach is that if we reach the wrong conclusion, we may come up with the wrong solution. Burkitt saw disease rates skyrocket after populations went from eating whole plant foods to refined plant and animal foods. But instead of telling people we should go back to eating whole plant foods, he was so convinced fiber was the magic component that his top recommendation was to eat whole grain bread—though they never used to eat any kind of bread in Uganda—and sprinkle some spoonfuls of wheat bran on your food.

However, studies to this day associating high fiber intake with lower risk of disease and death relate only to fiber from food intake rather than from fiber isolates or extracts. It is not at all clear whether fiber consumed as a supplement is beneficial. In retrospect, it might have been a mistake “to isolate fiber from the overall field of plant food nutrition.” The evidence supporting the value of fruits, vegetables, and whole grains, as opposed to only fiber, has proved to be much more consistent. Whole plant foods are of fundamental importance in our diet. Fiber is just one of the beneficial components of fruits, vegetables, nuts, grains, and beans. “Much of the effort on defining fiber and studying the fiber isolate would have been better applied to a whole-plant-food approach.”

What would have happened if Burkitt and others had emphasized instead the value of plant foods? The value of eating unrefined plant food, which incorporates fiber and phytonutrients, might have been the focus of attention rather than just isolated fiber, which led to people shopping for their fiber in the supplement aisle instead of the produce aisle.


My Solving a Colon Cancer Mystery video is a perfect example of the concept I presented here. If fiber were really the key, then sub-Saharan Africa would be rife with colorectal cancer these days.

For an extreme example, how about disease reversal with a diet centered on white rice? See Kempner Rice Diet: Whipping Us into Shape and Drugs and the Demise of the Rice Diet.

My video The 5-to-1 Fiber Rule discusses a way to identify less processed foods using fiber as a marker of whole foods.

For more intrigue in the world of fiber, check out Does Fiber Really Prevent Diverticulosis?.

And, if you’re thinking, “Dr. Who?,” then, for a historical perspective, see Dr. Burkitt’s F-Word Diet.

In health,
Michael Greger, M.D.

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