After Dr. Dean Ornish conquered our number-one killer, heart disease, he moved on to killer number-two. What happens if cancer is put on a plant-based diet? Ornish and colleagues found that the progression of early-stage prostate cancer could be reversed with a plant-based diet and other healthy lifestyle behaviors.

If the blood of those eating the Standard American Diet is dripped onto cancer cells growing in a petri dish, cancer growth is cut down about 9 percent. And if they’ve followed a plant-based diet for a year? Their blood can slash cancer growth by 70 percent. So the blood circulating throughout the bodies of those eating plant-based diets had nearly eight times the stopping power when it came to suppressing cancer cell growth.

That was for cell growth of prostate cancer, the leading cancer-killer specific to men. In younger women, breast cancer is the top cancer-killer. Researchers wanted to repeat the study with women using breast cancer cells, but they didn’t want to wait a whole year to get the results. Women are dying now. So they figured they’d see what a plant-based diet could do after just two weeks against three different types of human breast cancer.

As you can see in my video How Not to Die from Cancer, the study showed cancer growth started out at 100 percent, but then dropped after the subjects ate a plant-based diet for 14 days. A layer of breast cancer cells was laid down in a petri dish, and then blood from women eating the Standard American Diet was dripped on it. As you can see in the video, even the blood of women eating pretty poor diets had some ability to break down cancer. After just two weeks of eating healthfully, though, blood was drawn from those same women—so they effectively acted as their own controls—and was dripped on a new carpet of breast cancer cells. You can see for yourself that only a few individual cancer cells remained. Their bodies cleaned up. After only 14 days on a plant-based diet, their bloodstream became that much more hostile to cancer.

Slowing down the growth of cancer cells is nice, but getting rid of them all together is even better. This is what’s called apoptosis, programmed cell death. After eating healthfully, the women’s own bodies were able to somehow reprogram the cancer cells, forcing them into early retirement.

In my video, you can see what’s called TUNEL imaging, which allows researchers to measure DNA fragmentation, or cell death. With this technology, dying cancer cells appear as little white spots. From the start of the study, you can see one small white speck in the upper left of the image, showing that the blood of an average woman on a typical American diet can knock off a few breast cancer cells. After 14 days of healthy, plant-based living, however, her blood turned that one small white speck into a multitude of white spots. It’s as if she’s an entirely different woman inside! The same blood now coursing through these women’s bodies gained the power to significantly slow down and even stop breast cancer cell growth after just two weeks of eating a plant-based diet.

What kind of blood do we want in our body? What kind of immune system? Do we want blood that just rolls over when new cancer cells pop up, or do we want blood circulating to every nook and cranny of our body with the power to slow down and stop them?

The dramatic strengthening of cancer defenses shown in the study was after 14 days of a plant-based diet—and exercise.The researchers had the women walking 30 to 60 minutes a day. Given there were two factors, how do we know what role the diet played? Researchers decided to put it to the test.

In my video, you can see a chart that first shows how blood taken from those who ate a plant-based diet and had a routine of mild exercise, such as walking every day, over an average of 14 years, exhibited significant cancer cell clearance. The researchers then compared the substantial cancer-stopping power of plant eaters to that of an average sedentary American, which you can see is basically nonexistent.

The researchers also analyzed a third group. Instead of 14 years on a plant-based diet, they had 14 years on a Standard American Diet, but they also had 14 years of daily, strenuous, hour-long exercise, like calisthenics. They wanted to know if you exercised hard enough and long enough could you rival some strolling plant eaters.

The answer? There’s no question that exercise helped, but literally 5,000 hours in the gym was no match for a plant-based diet.

Once again using TUNEL imaging to analyze cancer cell death, the researchers found that even if you are a couch potato eating fried potatoes, your body isn’t totally defenseless. Your bloodstream can kill off some cancer cells, which you can see in my video as a couple white spots in the first image of that series. If you exercise for 5,000 hours, you can kill many more cancer cells, evidenced by the many more white specks appearing throughout that image. But nothing appears to kick more cancer tush than a plant-based diet, as that image is filled with white spots indicating cancer cells killed off.

Why is this the case? We think it’s because animal proteins, such as meat, egg white, and dairy protein, increase the level of insulin-like growth factor-1 (IGF-1), a cancer-promoting growth hormone involved in the “acquisition or progress of malignant tumors.”

In my video, you can see the results of a study that nailed IGF-1 as the villain. Just as in the previous studies, subjects went on a plant-based diet and cancer-cell growth dropped, while cancer-cell death shot up. This experiment, however, had a kicker: It added back to the cancer just the amount of IGF-1 that had been banished from your body as a result of eating and living healthier. In doing so, it effectively erased the “diet and exercise” effect. It’s as if the subjects had never started eating healthfully at all, with the cancer-cell growth rates and death rates returning to the same levels as before the plant-based diet intervention.

The reason one of the largest prospective studies on diet and cancer found “the incidence of all cancers combined was lower among vegetarians than among meat eaters” may be because they eat less animal protein, and thereby end up with less IGF-1, which means less cancer growth.

How much less cancer growth? A study found that middle-aged men and women with high protein intakes had a 75 percent increase in overall mortality and a fourfold increase in the risk of dying specifically from cancer. Does the protein source matter? Yes. It was specifically animal protein, which makes sense, given their higher IGF-1 levels.

The academic institution where the study was done sent out a press release with a memorable opening line: “That chicken wing you’re eating could be as deadly as a cigarette.” It went on to explain that “eating a diet rich in animal proteins during middle age makes you four times more likely to die from cancer…—a mortality risk factor comparable to smoking.”

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 it was “‘potentially even dangerous’ to compare the effects of smoking with the effect of meat and cheese,” but why? Because, they argued, 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 second-hand smoke. The ad included a chart with “everyday activities” and “reported relative risk,” in an attempt to say second-hand smoke wasn’t all that bad. The chart showed that while it increases the risk of lung cancer by 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. Lung cancer risk could be doubled if you frequently cook with oil, and heart disease risk tripled if you eat non-vegetarian or multiplied six-fold by eating lots of meat and dairy. Philip Morris’s conclusion? “Let’s keep a sense of perspective.” The “risk of lung cancer from second-hand tobacco smoke [was put] well below the risk reported by other studies for many everyday items and activities.”

That’s like saying, “Don’t worry about getting stabbed, because getting shot is so much worse.” Two risks don’t make a right.

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

The first time someone visits NutritionFacts.org can be overwhelming. With videos on more than 2,000 health topics, where do you even begin? Imagine stumbling onto the site not knowing what to expect and the new video-of-the-day is about how a particular spice can be effective in treating a particular form of arthritis. It would be easy to miss the forest for the trees, which is precisely why I created a series of overview videos that are essentially taken straight from my live, hour-long 2016 presentation How Not to Die: Preventing, Arresting, and Reversing Our Top 15 Killers.

The other videos in this overview series are:

Inspired to learn more about the role diet may play in preventing and treating cancer? Check out these other popular videos on the topic:

I’ve also produced an entire series on mammograms. You can find all of those videos here.

In health,

Michael Greger, M.D.