Thursday Nov 26, 2015 (foodconsumer.org) -- A meta-analysis of data from 18 cohort and case-control studies suggests that intake of vitamin C may reduce risk of prostate cancer.  A study of the data from case-control studies finds that those who had 150 mg of vitamin C per day (which is fairly low) were 20% less likely to develop prostate cancer. Vitamin C is also known as ascorbic acid.

Xiao-Yan Bai, Xinjian Qu, Xiao Jiang, Zhaowei Xu, Yangyang Yang, Qiming Su, Miao Wang, and Huijian Wu, Association between Dietary Vitamin C Intake and Risk of Prostate Cancer: A Meta-analysis Involving 103,658 Subjects, J Cancer. 2015; 6(9): 913–921.online 2015 Jul 28. doi:  10.7150/jca.12162

Another study of two lines of prostate cancer cells (androgen independent and androgen dependent) shows that vitamin C can inhibit cell division and growth of prostate cancer cells.  This inhibition was found due to hydrogen peroxide produced from vitamin C.  The inhibition was dose and time dependent.

Carlos Maramag, Mani Menon, K.C. Balaji, Premveer G. Reddy and Seethalakshmi Laxmanan, Effect of vitamin C on prostate cancer cells in vitro: Effect on cell number, viability, and DNA synthesis, the Prostate, Volume 32, Issue 3, pages 188–195, 1 August 1997