JUNE 29: PROSTABLOG NZ: Is NZ Herald columnist Deborah Coddington right when she warns of a prostate cancer risk from the mandatory addition of folic acid to bread?
In her column today, titled Spoonful of meddling helps the medicine go down, she writes:
The New Zealand Food Safety Authority warns we won’t know the effect of this for at least another generation, but studies are looking at links between excess folic acid and colon and prostate cancer.
A read of the authority’s website shows the risk appears to be insignificant, if a 274-page Food Standards Australia New Zealand report called FINAL ASSESSMENT REPORT, PROPOSAL P295, Consideration of Mandatory Fortification with Folic Acid, dated October, 2006, is anything to go by. It says, in part:
One trial and three cohort studies found no significant association between serum folate levels and incidence of prostate cancer. A large Swedish study, however, did observe a significant association between higher serum folate levels and increased risk of prostate cancer but only among study participants with a particular genetic make-up. In this study, ‘higher’ folate levels were below the pre-voluntary fortification mean in a Perth cohort.
Based on these findings, and the lack of intake studies, the evidence base is not sufficient to draw a conclusion about the relationship of folic acid and increased risk of prostate cancer.
The results of more recent studies on the incidence of all cancers and cancer of the prostate, breast and colorectum do not alter the conclusion reached in earlier reviews (SACN, 2004; SACN, 2005; Sanjoaquin et al., 2005e) that there is no apparent increase in risk associated with higher folic acid intakes for the population as a whole. Many of the studies suggest that some reduction in cancer risk might occur, however, most of these are observational and so might be affected by uncontrolled confounding factors.
[Following analysis of a number of studies]…In summary, the only study with intakes that are relevant for consideration to mandatory fortification reported a non-significant 11% increase in risk; the serum studies all report a non-significant associations ranging from a 15% decrease to a 20% increase in risk with higher levels. Given this, and lack of intake studies, the evidence base is not sufficient to allow a conclusion to be drawn regarding the relationship of folic acid to the incidence of prostate cancer.
But, the March 10, 2009, issue of the US Journal of the National Cancer Institute was widely reported for this publication:
Data regarding the association between folate status and risk of prostate cancer are sparse and conflicting.
We studied prostate cancer occurrence in the Aspirin/Folate Polyp Prevention Study, a placebo-controlled randomized trial of aspirin and folic acid supplementation for the chemoprevention of colorectal adenomas conducted between July 6, 1994, and December 31, 2006. Participants were followed for up to 10.8 (median = 7.0, interquartile range = 6.0–7.8) years and asked periodically to report all illnesses and hospitalizations.
Aspirin alone had no statistically significant effect on prostate cancer incidence, but there were marked differences according to folic acid treatment. Among the 643 men who were randomly assigned to placebo or supplementation with folic acid, the estimated probability of being diagnosed with prostate cancer over a 10-year period was 9.7% (95% confidence interval [CI] = 6.5% to 14.5%) in the folic acid group and 3.3% (95% CI = 1.7% to 6.4%) in the placebo group (age-adjusted hazard ratio = 2.63, 95% CI = 1.23 to 5.65, Wald test P = .01).
In contrast, baseline dietary folate intake and plasma folate in non-multivitamin users were inversely associated with risk of prostate cancer, although these associations did not attain statistical significance in adjusted analyses.
These findings highlight the potential complex role of folate in prostate cancer and the possibly different effects of folic acid–containing supplements vs natural sources of folate.