Monday June 2, 2014 (foodconsumer.org) -- A review in Advances in Clinical Chemistry suggests vitamin B12 and folate fortification may increase risk of prostate cancer, which is diagnosed in more than 230,000 American men each year, according to the Centers for Disease Control and Prevention.

The review led by S.M. Collin at School of Social & Community Medicine, University of Bristol in Bristol, United Kingdom shows that increased intake of folate and B12 was associated with slightly increased risk for prostate cancer.

Folate and vitamin B12 are potentially involved in prostate cancer development through genome-wide hypomethylation, gene-specific promoter hypermethylation, and DNA uracil misincorporation, according to the review.

Early studies yielded inconsistent conclusions on the association between intake of folate and vitamin B12 and risk of prostate cancer.  

A meta-analysis conducted by the study author shows high circulating levels of vitamin B12 and folate were associated with 10% and 18% increased risk of prostate cancer, respectively.

In another meta-analysis, Collin found both folate-pathway polymorphisms MTR 2756A > G and SHMT1 1420C > T associated with 6 and 11% increased risk for prostate cancer.

The author explains that the "positive association of circulating B12 with an increased risk of prostate cancer could be explained by reverse causality," but suggests further research needs to be conducted to rule out the causal effect of vitamin B12 in prostate cancer initiation and or progression.

Additionally, due to the link between folate and prostate cancer, the author says caution needs to be exercised for the mandatory folate fortification considering the prevalence of the disease is high and a slight effect would have a huge impact.

It should be noted that it remains unknown whether both synthetic and natural folate are associated with prostate cancer although studies have shown that synthetic, but not natural folate is associated with increased risk of breast cancer.

Likewise, it is unknown whether the form of B12, natural or synthetic, would make any difference.  Many vitamin B12 supplements are synthetic.   In any case, vitamin B12 is important, particularly for vegans because vitamin B12 is not present in vegetables and fruits.(David Liu, PHD)

Reference

Collin SM. Folate and B12 in prostate cancer. Advances in Clinical Chemistry. 2013;60:1-63.