Only about one in 10,000 people make it to be 100 years old. What’s their secret? Well, in 1993, a major breakthrough in longevity research was published: a single genetic mutation that doubled the lifespan of a tiny roundworm. Instead of all 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 medical marvel is the equivalent of producing a healthy 200-year-old human—all because of a single mutation? That shouldn’t happen; I mean, presumably, aging is caused by multiple processes, many genes. How could just knocking out one gene double the lifespan?

What is this aging gene, anyway? This 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. What is it? It’s the worm equivalent of the human IGF-1 receptor. And 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? No, we can turn on and off the expression of these genes, depending on what we eat. Three years ago, I profiled a remarkable series of experiments about IGF-1—insulin-like growth factor 1—this cancer-promoting growth hormone, released in excess amounts by our liver when we eat animal protein. So, men and women who don’t eat meat, egg whites, or dairy proteins have significantly lower levels circulating within their bodies.

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 growth, and then kill breast cancer cells off.

Similarly, the blood serum of men on plant-based diets suppresses prostate cancer cell growth about eight times better than before they changed their diet. This dramatic improvement in cancer defenses is, however, abolished if you add back just the amount of IGF-1 banished from their systems because they were eating and living healthier.

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 leads to a drop in cancer growth. An effect so powerful, Dr. Dean Ornish and colleagues appeared to be able to reverse the progression of prostate cancer without chemo, surgery, or radiation—just a plant-based diet, and other healthy lifestyle changes.

Now, 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—but also apparently makes you effectively cancer-proof. Not a single death from cancer in about 100 individuals with IGF-1 deficiency. How about 200 individuals? None developed cancer. See, most malignant tumors are covered in IGF-1 receptors. But if there’s no IGF-1 around, then they may not be able to grow and spread.

This may help explain why those eating low-carb diets appear to cut their lives short. But not just any low-carb diet—specifically those based on animal sources, whereas vegetable-based low-carb diets were associated with a lower risk of death.

But look, low-carb diets are high in animal fat, as well as animal protein. So, how do we know it wasn’t the saturated animal fat that was killing people off, and it had nothing to do with the protein? What we need is a study that just follows a few thousand people and their protein intakes for 20 years or so, and just see who lives longest, who gets cancer, who doesn’t. But, there’s never been a study like that—until now.

6,000 men and women over age 50 from across the U.S. were followed for 18 years, and those under age 65 with high protein intakes had a 75% increase in overall mortality, and a fourfold increase in the risk of dying from cancer. But not all proteins; these associations were either abolished or attenuated if the proteins were plant-derived. This all makes sense, given the higher IGF-1 levels among those eating lots of animal 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,” explaining that eating a diet rich in animal proteins during middle age makes you four times more likely to die from cancer than someone with a low-protein diet—a mortality risk factor comparable to smoking cigarettes. And when they say low-protein diet, what they actually mean is just getting the recommended amount of protein.

“Almost everyone is going to have a cancer cell or pre-cancerous 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.

“The question is not whether a certain diet allows you to do well in the short term,” one of the researchers noted. “But can it help you survive to be 100?” It wasn’t just more deaths from cancer; middle-aged people who eat lots of protein from animal sources were found to be more susceptible to early death in general. Crucially, the same did not apply to plant proteins, like beans. And it wasn’t the fat, but the animal protein that 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? Well, one nutrition scientist replied that it was potentially dangerous. It could damage the effectiveness of important public health messages. A smoker might think, “Why bother quitting smoking if my ham and cheese sandwich is just as bad for me?'”

It reminds me of a famous Philip Morris cigarette ad that tried to downplay the risks by saying, “Hey, you think second-hand smoke is bad, increasing the risk of lung cancer 19%; well, hey, drinking one or two glasses of milk may be three times as bad—62% increased risk of lung cancer. Or doubling the risk frequently cooking with oil; or tripling your risk of heart disease eating non-vegetarian; or multiplying your risk six-fold eating lots of meat and dairy.” So, they conclude, “Let’s keep some perspective here.” The risk of cancer from secondhand smoke may be well below that of other everyday activities. So, breathe deep.

That’s like saying: yeah, don’t worry about getting stabbed, because getting shot is so much worse. It’s like saying if you don’t wear seat belts, you might as well have unprotected sex. If you go bungee jumping, might as well disconnect your 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.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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