A number of extracts from cruciferous vegetables (such as broccoli, cauliflower, cabbage, etc.), particularly diindolylmethane (DIM), may explain the benefit of these vegetables on cancer progression, as it has been shown to inhibit multiple mechanisms of cancer growth.,
In a large cohort of over 35,000 men, use of grape seed extract supplements was associated with a 41% reduced risk of prostate cancer. It is thought to influence hormonal and inflammatory pathways.
Vitamin D levels are associated with risk of dying from prostate cancer. In a trial of men given 4000 IU per day for 1 year, vitamin D levels increased from 33ng/mL to 66ng/mL, over half had a decrease in the number of positive cores or Gleason score on biopsy.
Suggested dose is that sufficient to raise vitamin D blood levels to >40 ng/mL, which may require 5000 IU per day or more.