Transcript: Too Much Soy May Neutralize Benefits
We know what happens when men with active prostate cancer start eating a plant-based diet. The progression of their cancer appears to reverse, to get better—no drugs, no surgery, no radiation, just a vegan diet and other healthy lifestyle behaviors. Cancer markers in the control Standard American Diet group tend to get worse, and in the plant-based diet group, they tend to get better. The blood of those on a plant-based diet suppresses cancer growth about eight times better. We’re talking change on a genetic level—diet and lifestyle changes switching on and off gene expression, delaying or even avoiding the need for surgery and conventional chemo/radiation altogether.
I’ve already gone through that in videos past, but what if you did the same thing—men with prostate cancer, but this time, half in the control group, and half in not just a vegan diet group, but in a heavily soy-based vegan diet group. How much soy are we talking about? 7 to 18 servings a day, for an entire year. That’s like entire blocks of tofu, or 7 to 18 glasses of soy milk—that’s like four quarts a day, all year round. What do you think happened to their IGF levels at the end?
The IGF-1 levels in the control group in the study didn’t drop at all; started high, stayed high. In a varied vegan diet—protein from multiple plant sources, all different kinds of beans, whole grains, etc.—after years, you can see IGF-1 levels drop like this, from baseline.
What happened to the drowning-in-soy vegan group? Did their levels drop too? With that much added soy, the vegans in the study got literally pounds of more protein in their diets than the meat-eaters, but it was all added plant protein.
Soy, however, is one of those rare plants that mimics the protein profile of meat. So with that much more animal-type protein in their diet, were they even worse?
Surprisingly, they ended up with values about the same as the meat-eaters. But, wait a second. In Asian countries, where they eat the most soy, they’ve traditionally had just a fraction of our breast and prostate cancer rates.
Well, the researchers found something interesting. The isoflavones, the phytoestrogens in soy, may actually bump up production of IGF-binding protein. So even though they had similar levels of IGF in their blood, in those eating vegan, more of it may be bound up and unavailable to stimulate as much cancer growth.
Also, even in China and Japan, they don’t eat 7 to 18 servings of soy a day.
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.
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