While many here see merit in a whole foods, plant-based diet, a couple of our highly intelligent members here seem to scoff at the idea that it is PCa protective or that it is even particularly healthful to begin with. I have seen dismissal of Michael Gregor MD because of an assertion that he is blinded by a vegan bias. Certainly, I pay attention to these critics, but I respectfully tend to disagree. I'll be honest and say that I am less than 100% sure that Gregor is right most of the time, but I am more closely approximating that with each passing week.
Since the data of nutrition science is often way too complicated for me to fully appreciate, I rely more on the assessments of trusted others to help me form my impressions. Gregor and the couple of forum members I mentioned are among my trusted few. When their contentions are in disagreement, I'll tell you honestly that it has caused me a great amount of dissonance!
I have been on a plant-based diet for about a year now. It's impossible to tell whether it is helping keep my PCa from advancing, but it is clear to me that my health has benefited in other important ways. Examples: I have lost 30 pounds to get my weight in the ideal range and I no longer need drugs to control my cholesterol or blood pressure.
I believe Gregor has integrity. Evidence of that is in his reported business model. He apparently sells no products other than his recordings and book. He also apparently puts all proceeds back into his nutritionfacts.org which is not supported by advertisers and is totally free of charge. His latest short video discusses in part how the quality of a plant-based diet appears to matter when it comes to its capacity to slow and reverse advanced prostate cancer.
The cautions I've read here from some regarding controversial dietary advice for soy and flax seed consumption caused me to at first discontinue their use. The idea that the phytoestrogens in them might be harmful for PCa does indeed seem plausible. Now I'm back to using them, but with perhaps a bit more moderation. For me, Gregor's evidence-based encouragement of using them (with the caution that soy is probably currently best limited to 3-5 servings a day due to IGF-1 concerns) is a big factor in my plus column.