Introduction: Food Standards Australia New Zealand monitored the literature regarding cancer risk following mandatory fortification with folic acid to reduce the risk of neural tube defects in Australia.
Methods: Randomised controlled trials testing folic acid for at least one year and reporting any of: all-cause mortality, total cancer, four selected cancers or recurrence of colo-rectal adenoma in healthy non-pregnant adults were identified by searching in PubMed and CENTRAL from 2001 onwards. Random effects meta-analysis of the relative risks was conducted using StatsDirect (http://www.statsdirect.co.uk).
Results: 26 trials, lasting up to 7.3 years, were identified from 4216 abstracts. The larger trials generally described masked allocation and blind outcome assessment. The 13 trials (43,557 subjects) reporting total cancer incidence yielded a non-significant overall relative risk (RR) of 1.04 (95%CI: 0.97-1.11). Fewer studies reported results for colorectal cancer RR=1.00 (95%CI: 0.82-1.23), breast cancer RR=0.82 (95%CI: 0.63-1.07), lung cancer RR=1.00 (95%CI: 0.84-1.21) or prostate cancer RR=1.16 (95% CI: 0.85-1.60). Only the results for prostate cancer indicated any heterogeneity (I2=52.7%). Most data comes from large trials testing 0.8-2.5mg/day.
Conclusion: There are no significant increases or decreases in cancer risk. Other meta-analyses using different inclusion criteria to select studies have found similar results. The amount of folic acid used in mandatory fortification in Australia is about one-tenth of that tested and the effect on blood folate levels has been commensurately lower.
Funding source: None