In the community paper that arrived in our letterbox this morning there was a letter expressing very strong 'anti' feelings with regard to folate. The writer would, he said, boycott bread if this dreadful chemical was added. Google 'folate & prostate cancer', he said, & all would be revealed. (This was in reference to the original TV program, where one of the panel of 'analysts' commented on a purported link between folate & this particular cancer.)
The writer was probably referring to this item, on 'Newsmax.com', which describes a purported link between elevated folate. On the surface the reported data do suggest that too much folate could be harmful - but towards the end we see the following comment from the scientist who led this particular study: Alternatively, these results may be due to chance, and replication by other studies is needed. Not least because the sample size involved was quite small.
Funnily enough, that same initial google search delivers an earlier, much larger study (Stevens et al. 2006) published in the American Journal of Epidemiology, which notes that folate has important roles in DNA synthesis, repair, and methylation and is inversely associated with the risk of some cancers. Which is reasonable enough, given that the mutations underlying many cancers may involve a failure of DNA repair mechanisms. The research team goes on to say that neither dietary nor total folate intake (ie what someone gains in their diet, plus from supplementation) was associated with prostate cancer overall. However, higher folate levels were associated with a non-significant decreased risk of advanced prostate cancer.
In addition, using Google Scholar will take you to a series of meta-analyses that pool and examine data on the relationship between folate levels and various diseases (including cardiovascular disease and breast cancer) which indicate a causal protective effect of increasing folate intake. And the most recent of these analyses found no evidence supporting the claimed prostate cancer-high folate link.
But I guess the letter-writer didn't go that far. This does highlight one of the issues with google - that it's possible to 'educate' yourself on an issue without ever going deeply enough, or thinking critically about what's available. In this particular case, the Newsmax article may have confirmed an existing bias, & that's been enough for that individual. (And it reinforces my irritation that the TV program that stirred this up didn't even include a scientist on its 'panel'... *sigh*)
V.L.Stevens, C.Rodriguez, A.L.Pavluck, M.L.McCullough, M.J.Thun & E.E.Calle (2006) Folate nutrition and prostate cancer incidence in a large cohort of US men. American Journal of Epidemiology 163(11): 989-996. doi:10.1093/aje/kwj126