The Diet We Were Designed to Eat

There are three broad theories about evolution and food. One is that humans have become adapted to grains and other products of the agricultural revolution over the last 10,000 years. Two is the paleo view “that 10,000 years is a blink of an evolutionary eye, and that humans are adapted to paleolithic diets with a lot of lean meat,” but why stop there? The third theory is that the last 200,000 years “is a minute of the evolutionary year” when we were mostly Stone Age humans and represents just the last 1 percent of the roughly 20 million years we’ve been evolving since our common great ape ancestor. So, What Is the “Natural” Human Diet?

During our truly formative years, which one might say was the first 90 percent of our existence, our nutritional requirements reflected an ancestral past in which we ate mostly leaves, flowers, and fruits, with some bugs thrown in, thanks to wormy apples, to get our vitamin B12. “For this reason, another approach that might improve our understanding of the best dietary practices for modern humans is to focus attention not on the past but rather on the here and now; that is, on study of the foods eaten by the closest living relatives of modern humans,” given the bulk of our ancestral diets and “the lack of evidence supporting any notable diet-related changes in human nutrient requirements, metabolism, or digestive physiology” compared to our fellow great apes.

This could explain why fruits and vegetables are not only good for us but are vital to our survival. Indeed, we’re one of the few species so adapted to a plant-based diet that we could actually die from not eating fruits and vegetables, from the vitamin C-deficiency disease, scurvy. Most other animals simply make their own vitamin C, but why would our body waste all that effort when we evolved hanging out in the trees just eating fruits and veggies all day long?

Presumably, it’s not a coincidence that the few other mammals unable to synthesize their own vitamin C—including guinea pigs, some bunny rabbits, and fruit bats—are all, like us great apes, strongly herbivorous. Even during the Stone Age, data from rehydrated human fossilized feces tell us we may have been getting up to ten times more vitamin C and ten times more dietary fiber than we get today. The question is: Are these incredibly high-nutrient intakes simply an unavoidable by-product of eating whole, plant foods all the time, or might they actually be serving some important function, like antioxidant defense?

Plants create antioxidants to defend their own structures against free radicals. The human body must defend itself against the same types of pro-oxidants, so we too have evolved an array of amazing antioxidant enzymes, which are effective but not infallible. Free radicals can breach our defenses and cause damage that accumulates with age, leading to a variety of disease-causing and ultimately fatal changes. This is where plants may come in: “Plant-based, antioxidant-rich foods traditionally formed the major part of the human diet,” so we didn’t have to evolve that great of an antioxidant system. We could just let the plants in our diet pull some of the weight, like giving us vitamin C so we don’t have to be bothered to make it ourselves. Using plants as a crutch may well have relieved the pressure for further evolutionary development of our own defenses. That is we’ve become dependent on getting lots of plant foods in our diet, and when we don’t, we may suffer adverse health consequences.

Even during the Stone Age, this may not have been a problem. Only in recent history did we start giving up on whole plant foods. Even modern-day paleo and low-carb followers may be eating more vegetables than those on standard Western diets. There’s a perception that low-carbers are chowing down on the three Bs—beef, bacon, and butter—but that’s only a small minority. What they are eating more of is salad. Indeed, according to an online low-carb community, the number one thing they said they were eating more of was vegetables. Great! The problem isn’t people wanting to cut their carb intake by swapping junk food for vegetables. The concern is the shift to animal-sourced foods. “Greater adherence to [a low-carb diet] high in animal sources of fat and protein was associated with higher all-cause and cardiovascular mortality post-MI,” or after a heart attack, meaning they cut their lives short.

If there’s one takeaway from our studies of ancestral diets, perhaps it’s that “diets based largely on plant foods promote health and longevity.”


For more on the paleo and low carb diets, see:

If you were fascinated by how we can take advantage of plant defense mechanisms, check out my videos Appropriating Plant Defenses and Xenohormesis: What Doesn’t Kill Plants May Make Us Stronger.

How many antioxidants should we shoot for? See:

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 the Meat Industry Reacted to the New Cancer Warnings

What was the meat industry’s response to leading cancer charities’ recommendation to stop eating processed meat, like bacon, ham, hot dogs, sausage, and lunch meat? As I discuss in my video Meat Industry Reaction to New Cancer Guidelines, the industry acknowledges that the most recent international cancer prevention guidelines now urge people to avoid processed meat.

“It is evident that…such a statement represents ‘a clear and present danger’ for the meat industry,” reads one response in the journal Meat Science. However, processed meat, it continues, is “a social necessity.” (How could anyone live without bologna?) The challenge for the meat industry, the response outlines, is to find a way to maintain the consumption of these convenience products while somehow not damaging public health.

We’re still not sure what in processed meat is so carcinogenic, but the most probable educated guess for explaining the damaging effect of processed meats involves heme iron, along with nitrosamine and free radical formation, ultimately resulting in carcinogenic DNA damage. To reduce the nitrosamines, they could remove the nitrites, something the industry has been considering for decades because of the long-known toxic effects they cause. The industry adds them to keep the meat pink. There are, evidently, other coloring additives available. Nevertheless, it’s going to be hard to get industry to change “in view of the positive effects” of these substances as preservatives and in achieving a “desirable flavour and red colour developing ingredients.” No one wants green eggs and ham.

It’s like salt reduction in meat products. The meat industry would like to reduce it, but “[o]ne of the biggest barriers to salt replacement is cost as salt is one of the cheapest food ingredients available.” A number of taste enhancers can be injected into the meat to help compensate for the salt reduction, but some leave a bitter after-taste. To address that, industry can also inject a patented bitter-blocking chemical that can prevent taste nerve stimulation at the same time. This “bitter blocker is only the first of what will become a stream of products that are produced due to the convergence of food technology and biotechnology.”

The meat industry could always try adding non-meat materials to the meat, such as fiber or resistant starch from beans that have protective effects against cancer. After all, in the United States, dietary fiber is under-consumed by most adults, “indicating that fiber fortification in meat products could have health benefits.” But, of course, the meat industry’s own products are one of the reasons the American diet is so deficient in fiber in the first place.

The industry is all in favor of reformulating their products to cause less cancer, but “[o]bviously any optimization has to achieve a healthier product without affecting quality, particularly hedonic aspects.”

“It is important to realise that nutritional and technological quality [in the meat industry] are inversely correlated. Currently, improvement in one will lead to deterioration of the other.” Indeed, the meat industry knows that consumption of lard is not the best thing in the world—what with heart disease being our number-one killer—but those downsides “are in sharp contrast to their technological qualities that make them indispensable in the manufacture of meat products.” Otherwise, you just don’t get the same “lard consistency.” The pig’s fat doesn’t get hard enough, and, as a result, “a fatty smear upon cutting or slicing can be observed on the cutting surface of the knife.” Less heart disease versus absence of that fatty smear? I suppose you have to weigh the pros and cons…


According to the World Health Organization’s IARC, processed meat is now a Group 1 carcinogen—the highest designation. How is it that schools still feed it to our children?

How Much Cancer Does Lunch Meat Cause? Watch the video to find out.

For more on carcinogens, cancer, and meat, see:

Some of the meat industry’s finagling reminds me of tobacco industry tactics. See, for example, Big Food Using the Tobacco Industry Playbook and The Healthy Food Movement: Strength in Unity. You can also check out American Medical Association Complicity with Big Tobacco.

Skeptical about the danger of excessive sodium intake? Check out The Evidence That Salt Raises Blood Pressure. If you’re still not convinced, see Sprinkling Doubt: Taking Sodium Skeptics with a Pinch of Salt and Sodium Skeptics Try to Shake Up the Salt Debate. Why do the meat industries add salt when millions of lives are at stake? Find out in Big Salt: Getting to the Meat of the Matter.

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:

Meat Industry Response to Meat Being Labeled Carcinogenic

The most extensive report on diet and cancer in history is constantly being updated with all the new research. As I discuss in my video The Palatability of Cancer Prevention, in its update on colorectal cancer a few years ago, various meats were implicated, including processed meat as “a convincing cause of colorectal cancer,” which is its highest level of evidence that “effectively means ‘beyond reasonable doubt.’” More recently, processed meat was confirmed as a carcinogen by the World Health Organization. The main message was that “the best prevention of colorectal cancer is the combination of higher physical activity with a fibre-rich and meat products poor diet.” A decrease by half a turkey sandwich’s worth of meat might lower the total number of colorectal cancer cases by approximately 20 percent. There are several implications of this cancer guideline update, but a paper in the industry publication Meat Science decided “to focus on the consumer side of the story, since every consumer is a patient and vice-versa at some point in the future.” But chronic disease need not be invariably a consequence of aging.

“Although the epidemiological evidence for the relationship between colorectal cancer risk (at least!) and processed meats intake cannot be denied,” the Meat Science authors suggest further research. For example, compare the risk of consuming meat to other risky practices—alcohol, lack of physical activity, obesity, and smoking. Compared to lung cancer and smoking, maybe meat won’t look so bad!

Consumers, however, probably won’t even hear about the cancer prevention guidelines. “Consumers today are overloaded with information….It is thus probable that the dissemination of the [World Cancer Research Fund’s] update on colorectal cancer drowns in this information cloud.” And, even if consumers do see it, the meat industry doesn’t think they’ll much care.

For many consumers in the Western world, “the role of healthfulness, although important, is not close to taste satisfaction in shaping their final choice of meat and meat products…It is hence questionable that slightly revised recommendations based on the carcinogenic effects of meat consumption will yield substantial changes in consumer behavior.”

Doctors and nutrition professionals feed into this patronizing attitude that people don’t care enough about their health to change. A classic paper from The American Journal of Clinical Nutrition, a leading journal, scoffed at the idea that people would ever switch to a “prudent diet,” reducing their intakes of animal protein and fat no matter how much cancer was prevented. “The chances of reducing consumptions of fat, protein foods, or indeed of any food to a significant extent to avoid colon cancer are virtually nil.” Consider heart disease. We know we can prevent and treat heart disease with the same kind of diet, but the public won’t do it. “[T]he diet,” they said, “would lose too much of its palatability.”

“The great palatability of ham,” in other words, “largely outweighs other considerations…[although] health and wellbeing are increasingly important factors in consumer decisions.” A 1998 Meat Science article feared that “[u]nless meat eating becomes compatible…with eating that is healthy, wholesome, and safe, it will be consigned to a minor role in the diet in developed countries during the next decade.” That prediction didn’t quite pan out. Looking at a graph of total meat consumption per person over the last 30 years or so, intake rises and rises. In 1998, when that Meat Science article worrying about the next decade of meat consumption was published, we see intake rise even further. It does then seem to kind of flatten out before it starts falling off a cliff. Indeed, meat consumption dipped down about 10 percent  but has surged back up. Still, millions of Americans are cutting down on meat.

So don’t tell me people aren’t willing to change their diets. Nevertheless, we continue to get diluted guidelines and dietary recommendations, because authorities are asking themselves, “What dietary changes could become acceptable?” rather than just telling us what the best available science says and letting us make up our own minds about the cancer risk as we feed ourselves and our families.


How Much Cancer Does Lunch Meat Cause? Good question—watch the video!

Can simply cutting down on meat consumption extend our lifespan? Find out in Do Flexitarians Live Longer?. For my overview on cancer prevention, check out How Not to Die from Cancer.

I think the role of health authorities is to share with patients the pros and cons of all the options and let the patients, their families, and their doctors decide together what’s right for them. I’ve produced a number of videos on this issue, including:

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: