Canadian researchers looked at vitamin E, selenium and soy, taken daily for three years, provided no benefit to men who were at higher risk of developing the disease.
This study comes three years after a larger study of men also determined there was no benefit.
The results didn't rule out that soy might be beneficial to those who eat it frequently for decades. but three years of soy didn't appear to help.
The study appears in the Journal of Clinical Oncology.