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.