To maintain the low IGF-1 levels associated with a plant-based diet, one should probably eat no more than 3-5 servings of soy foods a day.
Images thanks to viviandnguyen_ via Flickr.
So we know 7 to 18 servings of soy a day may neutralize some of the beneficial effects of avoiding animal protein; at the same time studies have repeatedly found that women who eat lots of soy appear to have a lower risk of getting breast cancer and a better risk of surviving breast cancer than those who don’t. So is there some magic number of soyfood servings we should shoot for?
So far we know that somewhere between 7 and 18 is bad, so more than 18 definitely gets the axe. This two year study found no effect on IGF levels of adding 2 servings of soyfoods day, whether they were tofu, soymilk, soy nuts, or the concentrated soy isolate found plant-based meats, protein bars or protein powder (green with ? region shrinking).
Still got a big range here. This study suggested 5-10 servings a day was bad— increased IGF—so nutritional science has slowly but surely been narrowing it down. Same year in Japan, 3 servings a day cleared the IGF radar… And then… that’s it. That’s all we got so far.
The bottomline is that legumes should be a part of everyone’s daily diet, which means lentils, peas, and/or beans every day, of which soy is an excellent choice, but I recommend that we should probably stick to no more than 3-5 servings 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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This is the fourth in a string of videos on the role plant and animal proteins play in determining levels of the cancer-promoting growth hormone IGF-1. See Protein Intake and IGF-1 Production, Higher Quality May Mean Higher Risk, Animalistic Plant Proteins, and Too Much Soy May Neutralize Plant-Based Benefits. For the role soy plays in extending breast cancer survival, see my latest video on the subject Breast Cancer Survival and Soy. I've got two dozen other videos on soy (and hundreds of others on more than a thousand topics).
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