The question here is if adopting a healthier diet can fight prostate cancer. It is the same question men ask their doctors.
The definite answers are not yet in, but researchers found in several studies that in countries where men eat a large aount of meat (typical Western), there are more agressive prostate cancers than in countries where people eat more plant-based foods. Risk and causes are: obesity and weight; family history; prostate cancer is more likely to develop in older men and in non-Hispanic black men; some inherited faulty genes can increase your risk; being taller; hormone levels and pesticides.
If you would like to read more or you would like to know what a meal eating plan looks like, please continue reading here: https://www.health.harvard.edu/cancer/can-diet-help-fight-prostate-cancer or https://www.cancerresearchuk.org/about-cancer/prostate-cancer/risks-causes