Dialing Down the Grim Reaper Gene

Only about 1 in 10,000 people live to be a 100 years old. What’s their secret? I discuss this in my video Animal Protein Compared to Cigarette Smoking.

In 1993, a major breakthrough in longevity research was published about a single genetic mutation that doubled the lifespan of a tiny roundworm. Instead of all worms being dead by 30 days, the mutants lived 60 days or longer. This lifespan extension was “the largest yet reported in any organism.” This methuselah worm, a “medical marvel,” is “the equivalent of a healthy 200-year-old human.” All because of a single mutation? That shouldn’t happen. Presumably, aging is caused by multiple processes, affected by many genes. How could knocking out a single gene double lifespan?

What is this aging gene—a gene that so speeds up aging that if it’s knocked out, the animals live twice as long? It’s been called the Grim Reaper gene and is the worm equivalent of the human insulin-like growth factor 1 (IGF-1) receptor. Mutations of that same receptor in humans may help explain why some people live to be a hundred and other people don’t.

So, is it just the luck of the draw whether we got good genes or bad ones? No, we can turn on and off the expression of these genes, depending on what we eat. Years ago I profiled a remarkable series of experiments about IGF-1, a cancer-promoting growth hormone released in excess amounts by our liver when we eat animal protein. Men and women who don’t eat meat, egg white, or dairy proteins have significantly lower levels of IGF-1 circulating within their bodies, and switching people to a plant-based diet can significantly lower IGF-1 levels within just 11 days, markedly improving the ability of women’s bloodstreams to suppress breast cancer cell growth and then kill off breast cancer cells.

Similarly, the blood serum of men on a plant-based diet suppresses prostate cancer cell growth about eight times better than before they changed their diet. However, this dramatic improvement in cancer defenses is abolished if just the amount of IGF-1 banished from their systems as a result of eating and living healthier is added back. This is one way to explain the low rates of cancer among plant-based populations: The drop in animal protein intake leads to a drop in IGF-1, which in turn leads to a drop in cancer growth. The effect is so powerful that Dr. Dean Ornish and colleagues appeared to be able to reverse the progression of early-stage prostate cancer without chemotherapy, surgery, or radiation—just a plant-based diet and lifestyle program.

When we’re kids, we need growth hormones to grow. There’s a rare genetic defect that causes severe IGF-1 deficiency, leading to a type of dwarfism. It also apparently makes you effectively cancer-proof. A study reported not a single death from cancer in about 100 individuals with IGF-1 deficiency. What about 200 individuals? None developed cancer. Most malignant tumors are covered in IGF-1 receptors, but if there’s no IGF-1 around, they may not be able to grow and spread.

This may help explain why lives appear to be cut short by eating low-carb diets. It’s not just any low-carb diet, though. Specifically, low-carb diets based on animal sources appear to be the problem, whereas vegetable-based low-carb diets were associated with a lower risk of death. But low-carb diets are high in animal fat as well as animal protein, so how do we know the saturated animal fat wasn’t killing off people and it had nothing to do with the protein? What we need is a study that follows a few thousand people and their protein intakes for 20 years or so, and sees who lives longest, who gets cancer, and who doesn’t. But, there had never been a study like that…until now.

Six thousand men and women over age 50 from across the United States were followed for 18 years, and those under age 65 with high protein intakes had a 75 percent increase in overall mortality and a fourfold increase in the risk of dying from cancer. Does it matter what type of protein? Yes. “These associations were either abolished or attenuated if the proteins were plant derived,” which makes sense given the higher IGF-1 levels in those eating excess protein.

The sponsoring university sent out a press release with a memorable opening line: “That chicken wing you’re eating could be as deadly as a cigarette.” It explained that “eating a diet rich in animal proteins during middle age makes you four times more likely to die of cancer than someone with a low-protein diet—a mortality risk factor comparable to smoking.” And when they say “low-protein diet,” what they actually mean is getting the recommended amount of protein.

“Almost everyone is going to have a cancer cell or pre-cancer cell in them at some point. The question is: Does it progress?” said one of the lead researchers. That may depend on what we eat.

“[T]he question is not whether a certain diet allows you to do well for three days,” a researcher noted, “but can it help you survive to be 100?” Excessive protein consumption isn’t only “linked to a dramatic rise in cancer mortality, but middle-aged people who eat lots of proteins from animal sources…are also more susceptible to early death in general.” Crucially, the same didn’t apply to plant proteins like beans, and it wasn’t the fat; the animal protein appeared to be the culprit.

What was the response to the revelation that diets high in meat, eggs, and dairy could be as harmful to health as smoking? One nutrition scientist replied that it was potentially dangerous because it could “damage the effectiveness of important public health messages.” Why? Because a smoker might think “why bother quitting smoking if my cheese and ham sandwich is just as bad for me?”

This reminds me of a famous Philip Morris cigarette ad that tried to downplay the risks of smoking by saying that if we think second-hand smoke is bad, increasing the risk of lung cancer 19 percent, drinking one or two glasses of milk every day may be three times as bad with a 62 percent higher risk of lung cancer. What’s more, doubling the risk is frequently cooking with oil, tripling our risk of heart disease is eating non-vegetarian, and multiplying our risk six-fold is eating lots of meat and dairy. So, they conclude, “Let’s keep a sense of perspective.” The ad goes on to say that the risk of cancer from second-hand smoke may be “well below the risk reported…for many everyday items and activities.” So, breathe deep!

That’s like saying we shouldn’t worry about getting stabbed because getting shot is so much worse. Or, if we don’t wear seatbelts, we might as well have unprotected sex. If we go bungee jumping, we might as well disconnect our smoke alarms at home. Two risks don’t make a right.

Of course, you’ll note Philip Morris stopped throwing dairy under the bus once they purchased Kraft Foods.


The IGF-1 story is so pivotal that it’s one of the first video series I ever produced for NutritionFacts.org. I’m so glad I was able to release this long-awaited update. If you want a blast from the past, watch the original series starting with Engineering a Cure.

For more parallels between the tobacco industry and the food industry, see:

What about the mobile phone industry? Does Cell Phone Radiation Cause Cancer?

For more on healthy aging and longevity, see:

It’s important to note the so-called low protein intake is actually the recommended protein intake, which is associated with a major reduction in cancer and overall mortality in middle age, under age 65. But did you notice that it says not among older individuals? All of this is covered in my video Increasing Protein Intake After Age 65.

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: