You may have heard the expression “knowledge is power.” Well – today – we’re going to give you more power to control your diet and lifestyle – by giving you the facts. Welcome to the Nutrition Facts podcast. I’m your host – Dr. Michael Greger.
Today we continue our series – looking at the human health effects – of plant- based meats.
We start out with the effects of plant-based meats on premature puberty, childhood obesity, and hip fracture risk.
As noted in an editorial in the Journal of the American Medical Association on plant-based meat alternatives, just looking at the nutrition facts info of a regular burger versus Beyond Meat or the Impossible Burger, you wouldn’t necessarily be able to predict the health consequences without further studies. But we’ve had plant-based meat alternatives for over a century. I mean, who wouldn’t want a can of good eatin’ Protose? It is, after all, the modern vegetable meat patent filed by Dr. John Harvey Kellogg in 1899.
Of course, “products such as tofu and tempeh have existed in Asia for centuries,” but I think of those as separate foods in their own right, as opposed to products intentionally designed to mimic the taste and texture of meat. With such a rich history, harkening back to the days of pass-the-Proteena, you’d think there’d be some studies of consumers. And indeed, there are. For example, girls who eat meat may start their periods six months earlier than girls who don’t. Is it just because they’re eating lots of protein and fat? Evidently not, because girls who instead are eating meat analogues, like veggie burgers and veggie dogs, are able to delay menstruation by nine months. Of course, it’s hard to tease out how much of that is just from avoiding meat. But compared with girls who eat meat just a few times a week, those who ate meat a few times a day had a significantly earlier age of first menstruation, which also may help provide an explanation for why childhood meat consumption is linked to breast cancer later in life, since the earlier you start your period, the higher your lifetime risk.
Now, obesity itself may contribute to the early onset of puberty in girls. So, that could be another factor. Studies have suggested vegetarian children tend to be leaner than nonvegetarian children. They aren’t smaller in general, though. Vegetarian boys and girls may measure up to be about an inch taller than their classmates; they just aren’t as wide. So, the fact that girls who eat plant-based meats may be less likely to suffer from premature puberty may, in part, be because they were leaner.
Indeed, childhood obesity research found meat consumption seemed to double the odds of schoolchildren becoming overweight, compared to the consumption of plant-based meat. Now, whole plant food sources of protein, such as beans, did even better though, associated with cutting in half the odds of kids becoming overweight. So, that’s why I consider these kinds of plant-based meats more of a useful stepping stone towards a healthier diet, rather than the endgame ideal. The same amount of protein in a bean burrito would be better in nearly every way.
Similarly, in terms of hip fracture risk, in the Adventist 2 study following tens of thousands of men and women for years, daily intake of plant-based meats appeared to reduce the risk of hip fracture by nearly half; but daily legume intake—beans, split peas, chickpeas, and lentils—may drop risk of hip fracture by even more, nearly two thirds.
In our next story, clinical trials on Quorn show that it can improve satiety and help people control cholesterol, blood sugar, and insulin levels.
You may have heard about meat made out of wheat protein, meat made out of soybean protein, and meats made out of pea protein, but mycoprotein is a relatively new addition. Meat made from the mushroom kingdom, popular in Europe, commercialized as Quorn, which makes not just meat-free beef, but chicken-free chicken, fish-less fish, and pig-free pork––just in case someone would like to eat plant-based, but can’t give up their cocktail weenies.
Environmental impact-wise, Quorn beef has at least a 10 times smaller carbon footprint than that of beef; Quorn chicken at least four times better than chicken-chicken. And health-wise, it’s high in protein and fiber, and low in fat, cholesterol, sodium, and sugar, as one would expect. But, most importantly, there have been clinical trials showing it may help people control cholesterol, blood sugar, and insulin levels, and improve satiety. No surprise given that not only the fiber but the mycoprotein itself is fermentable by our good gut bugs, so can also act as a prebiotic for our friendly flora.
There have been rare authenticated reports of people with mycoprotein allergies, and even more with unvalidated complaints, but given how many billions of packages have been sold, the rate of allergic reactions may be on the order of like 1 in 9 million.
Here’s the cholesterol data, converted into U.S. numbers. Significant drops in total and LDL cholesterol—more than 30 points within eight weeks.
In terms of satiety, both tofu and Quorn have been found to have satiating qualities that are stronger than chicken; for Quorn, among both lean subjects and overweight and obese individuals, cutting down on subsequent meal intake hours later.
You know, it’s funny, when the meat industry funds obesity studies on chicken, they choose for their head-to-head comparison foods like cookies and “sugar-coated chocolates.” This is a classic drug industry trick where you make your product look better by comparing it against something worse. (Apparently, just regular chocolate was not enough to make chicken look better.) But what happens when chicken is pitted against a real control, like chicken without the actual chicken? Chicken chickens out.
For example, feed people a chicken and rice lunch, and four and a half hours later, they eat 18 percent more of a dinner buffet than those who instead got a Quorn and rice lunch––cutting about 200 calories on average.
Part of the reason plant-based meats may be less fattening is that they cause less of an insulin spike. A meat-free chicken like Quorn causes up to 41 percent less of an immediate insulin reaction. It turns out animal protein causes almost exactly as much insulin release as pure sugar.
Just adding some egg whites to your diet can increase insulin output 60 percent within four days. And fish may be even worse.
Why would adding tuna to mashed potatoes spike up insulin levels, but adding broccoli instead drop the insulin response by about 40 percent? It’s not the fiber, since giving the same amount of broccoli fiber alone provided no significant benefit. So, why does animal protein make things worse, but plant protein makes things better?
Plant proteins tend to be lower in the branched-chain amino acids, which are associated with insulin resistance—the cause of type 2 diabetes. You can show this experimentally. Give some vegans branched-chain amino acids, and you can make them as insulin-resistant as omnivores. Or, take omnivores and put them through even a 48-hour vegan diet challenge, and within two days you can see the opposite—significant improvements in metabolic signatures. Why? Because “decreased consumption of branched-chain amino acids improves metabolic health.”
Those randomized to restrict their protein intake were averaging literally hundreds more calories per day; so, they should have become fatter, right? But no, they actually lost more body fat. Restricting their protein enabled them to eat more calories, while at the same time they lost more weight. More calories, yet a loss of body fat! And this magic “protein restriction”? They were just having people eat the recommended amount of protein. So, maybe they should have just called this the normal protein group, or the recommended protein group, and the group that was eating more typical American protein levels, and suffering because of it, the excess protein group.
Given the “restoration of metabolic health by decreased consumption of branched-chain amino acids,” leaders in the field have suggested the invention of drugs to block their absorption, to “promote metabolic health and treat diabetes and obesity without reducing caloric intake.” Or, we can just try not to eat so many branched-chain amino acids in the first place.
They are found mostly in meat, including chicken and fish, dairy products, and eggs, perhaps explaining why animal protein has been associated with higher diabetes risk, whereas plant protein appears protective. So, defining the “appropriate upper limits” of animal protein intake “may offer a great chance for the prevention of type 2 diabetes and obesity.”
Finally today, we ask – Is heme just an innocent bystander in the link between meat intake and breast cancer, diabetes, heart disease, stroke, and high blood pressure?
In an editorial in the Journal of the American Medical Association, the chair of nutrition at Harvard pointed out that many plant-based meat alternatives, such as Beyond Meat and the Impossible Burger, can be high in sodium. But an issue specific to the Impossible Burger was the heme they add, derived from soybean plants to enhance the product’s meaty flavor and appearance. Safety analyses have failed to find any toxicity risk specific to the soy heme they have yeast churn out. The FDA has agreed, both for use as a flavor and color enhancer: safe. In other words, just as safe as the heme found in blood and muscle in meat. But how much is that really saying?
The concern raised in the op-ed, for example, was that higher intake of heme has been associated with an elevated risk of developing type 2 diabetes. But not just diabetes, killer #7 in the United States. Higher dietary intake of heme iron is associated with an increased risk of cardiovascular disease as well: killers #1, #4, and #13 (heart disease, stroke, and high blood pressure). But, since heme is found mostly in meat, heme intake may just be a marker for meat intake. It’s like with diabetes: three meta-analyses published to date, and they all reported the same link. But there’s lots of reasons why meat may increase diabetes risk, like advanced glycation end products, produced when animal products are baked, broiled, grilled, fried, or barbequed. So, how do we know that heme isn’t just some innocent bystander?
The same issue arises with the link between heme intake and increased breast cancer risk. Since heme iron is coming from animal foods, it could be any of the other meat components––like animal fat or meat mutagens––compounds in meat that can cause DNA mutations. And hey, what about all the hormonal steroids implanted into cattle that may play a role in the development of breast cancer? A study in Japan found that beef imported from the United States contained up to 600 times the levels of estrogens, like estradiol. And, “higher consumption of estrogen-rich beef due to hormone [implantation] might facilitate estrogen accumulation in the [human] body and thus affecting women’s risk for breast cancer.” So yeah, heme iron intake was associated with breast cancer risk, but maybe that’s just because the heme and the hormones are traveling together in the same package: meat.
The NIH-AARP study is the largest prospective study on diet and health ever, following more than a half million men and women for over a decade now. With such a huge dataset, they could take advantage of the fact that different meats have different amounts of heme; so, they could try to tease out the heme components by, in effect, comparing people eating different amounts of heme, but the same amount of meat, to see if heme is independently associated with disease. And indeed, that’s what they showed: an independent association not only from nitrites in processed meat, but heme and mortality from almost all causes: death from diabetes, heart disease, stroke, respiratory disease, kidney disease, liver disease, cancer, and all causes put together. They calculated that about one-fifth of the association between, like, eating burgers and the shortening of your lifespan could be statistically accounted for by just the heme itself. But that’s assuming cause and effect. Even an “independent association” is still an association. You can’t prove cause and effect until you put it to the test in interventional studies.
Normally, we don’t necessarily care about the mechanism. When the World Health Organization designated bacon, ham, hot dogs, luncheon meat, and sausage to be Group 1 carcinogens, meaning we know these products cause cancer in human beings, who cares if it’s the heme iron, or the heterocyclic aromatic amines, or the polycyclic aromatic hydrocarbons, or the N-nitrosamines. They’re all wrapped up in the same place—processed meat—which we know causes cancer. So, we should just try to stay away from it, regardless of the mechanism. But with the advent of the Impossible Burger, we really do have to know, because for the first time we have lots of heme without any actual meat.
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