Hi Dave,
If there was some food or supplement that really whacked out P.Ca. I'd think we'd know about it.
Citrus Pectin has been looked at but in the quantities we could actually consume it hasn't proven a definite advantage. That said, lemon is good for you in sensible quantities.
Oregano was discussed on the forum a few years ago. Like mint & some other herbs it helps reduce inflammation. Particularly if you eat meat & cheese. ( Lamb + mint sauce has merit to reduce the fattiness ). It is understood now that reducing inflammation helps us.
These are sometimes recommended :
Curcumin
Resveratrol
Fish oil
Possibly Pomegranate juice ( although no proven studies I know of )
Avoiding inflammatory foods.
If you eat a high meat & Dairy diet & egg yolk diet , then an anti-inflammatory supplement could help a bit.
Some us just try to avoid the inflammatory foods which may help progression of P.Ca.
There is /was a cocktail of herbs ( Zyflemed (sp ? ) which some men have tried. Again, if your diet is Omega 6 rich & you eat meat & dairy then such things might reduce inflammation a bit. Avoidance just seems easier.
Problem is, getting such herbs & spices in the digestive system into the P.Ca. cells to do actual damage. Thus slowing progression is likely the best we can get from such supplements. By altering the environment in which the P.Ca. has thrived pre-diagnosis.