(2 mins) Transcript. Dr Greger's summary: "While animal proteins increase levels of the cancer-promoting growth hormone IGF-1, and most plant proteins bring levels down, 'high quality' plant proteins, such as soy, may not significantly affect levels in either direction. This, however, may depend on the quantity consumed."

(3 mins) Transcript. Dr Greger's summary: "Vegans consuming 7 to 18 servings of soy foods a day may end up with circulating IGF-1 levels comparable to those who eat meat."

(2 mins) How Much Soy Is Too Much? (Oct 2012). Dr Greger's summary: "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."

Dr Greger says,