The Answer to the Pritikin Puzzle

Remember the Pritikin experiments? You put people on a plant-based diet and exercise, and in as little as 12 days, you can turn their bloodstream into a cancer cell fighting machine. Here’s the before picture. A layer of breast cancer cells is laid down in a petri dish, and then blood from women eating the Standard American Diet is dripped on them. And, as you can see, even people eating crappy diets have some ability to break down cancer. But after just 12 days eating healthy, blood was drawn from those same women, dripped on another carpet of breast cancer cells, and this is what you’re left with. Their bodies cleaned up!

You can also look at it another way. This is what’s called terminal-deoxynucleotidyl-transferase-dUTP-nick-end-labeling, or “TUNEL” imaging, which measures DNA fragmentation—cell death. Dying cells show up as white spots. So again, this is the before—what the blood of your average woman can do to breast cancer cells. It can kill a few. But then, after 12 days of healthy plant-based living, their blood can do this.

This is that programmed cancer cell death. After eating healthy, their own bodies were able to reprogram the cancer cells, forcing them into early retirement. It’s like you’re an entirely different person inside.

How does a simple dietary change make one’s bloodstream so inhospitable to cancer, in just a matter of days? That was the next question they set out to answer, and they finally did, in 2011. “Here we sought to determine the underlying mechanisms for these anticancer effects.” And what they came up with was IGF-1.

If you measure the blood levels of insulin-like growth factor-1 before and after 11 days on a plant-based diet with exercise, IGF-1 levels significantly drop. And IGF-1 binding protein levels significantly rise. That’s one way our body tries to protect itself from cancer—from excessive growth—by releasing a binding protein into the bloodstream to tie up IGF-1. It’s like our body’s emergency brake.

Yeah, sure, in as little as 11 days, a healthy diet can reprogram our body to slow down IGF-1 production, but you still have all that IGF-1 circulating in your bloodstream from the bacon and eggs you had the week before. So, your liver releases the snatch squad of binding proteins that take it out of circulation pronto. Exercise alone can drop IGF-1 levels, but you need the plant-based diet to get those kind of snatch squad levels.

And so, with that combination, 20% less IGF-1, and 50% more IGF binding protein—no wonder there was such a dramatic cancer cell die-off after just a few days.  

So, did they solve the riddle? Did they figure out how a plant-based diet shuts down cancer growth? Well the definitive study wasn’t published until recently.

Same as last time; before and after a few weeks of a plant-based diet. Cancer cell growth drops, and programmed cancer cell death shoots up. But then, here’s the kicker. Remember how IGF-1 levels dropped? Well, what if you added back to the cancer the exact same amount of IGF-1 banished from your body, because of the healthy diet? What if you added that back in with the cancer? It erases the diet and exercise effect. It’s like you never started eating healthy at all.

Now, if cancer growth just came back down to here, you’d be like, okay, IGF-1 was part of it. But the fact that it eliminated the effects of the lifestyle changes suggests that it was the mechanism all along.

Walking and eating a plant-based diet for just a few days lowers circulating IGF-1 levels, which then can reverse cancer growth.

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 Kerry Skinner.

Please consider volunteering to help out on the site.

• Barnard RJ, Gonzalez JH, Liva ME, Ngo TH. Effects of a low-fat, high-fiber diet and exercise program on breast cancer risk factors in vivo and tumor cell growth and apoptosis in vitro. Nutr Cancer. 2006;55(1):28-34.
• Soliman S, Aronson WJ, Barnard RJ. Analyzing Serum-Stimulated Prostate Cancer Cell Lines After Low-Fat, High-Fiber Diet and Exercise Intervention. Evid Based Complement Alternat Med. 2009 Apr 17.
• Ngo TH, Barnard RJ, Tymchuk CN, Cohen P, Aronson. Effect of diet and exercise on serum insulin, IGF-I, and IGFBP-1 levels and growth of LNCaP cells in vitro (United States). Cancer Causes Control. 2002 Dec;13(10):929-35.
• McCarty MF. Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity. Med Hypotheses. 1999 Dec;53(6):459-85.

• breast cancer
• breast health
• cancer
• exercise
• IGF-1
• Plant-Based Diets
• Pritikin
• standard American diet
• women's health