Colorectal cancer incidence in Australia before and after mandatory fortification of bread flour with folic acid

Objective: Mandatory fortification of bread flour with folic acid has helped to reduce the incidence of neural tube defects in several countries. However, it has been suggested that folic acid may have potential adenoma-promoting effects, and reports from some countries have suggested that mandatory folic acid food fortification programmes have increased the incidence of colorectal cancer. The objective of this study was to evaluate colorectal cancer incidence patterns before and after introduction of mandatory folic acid fortification of bread flour in Australia in 2009. Design: Data from the Australian Cancer Database were used to plot age-standardised incidence of colorectal cancer. We calculated age-adjusted rate ratios with 95 % CIs. Setting: Australia. Participants: We used population-level aggregate data obtained from cancer registries. Results: Age-standardised colorectal cancer incidence generally decreased between 1999 and 2016. Although there was a slight increase in rates in 2010 compared with 2009 (62·8 v. 61·6 cases per 100 000, age-adjusted rate ratio 1·02 (95 % CI 0·99, 1·04), joinpoint regression indicated decreases of –0·4 % (95 % CI –0·7, 0·0) per year from 1999 to 2010 and –2·2 % (95 % CI –3·1, –1·3) per year from 2010 to 2016. Conclusions: While causation cannot be assessed from these population-level data, our observations indicate that there is no evidence that introduction of mandatory folic acid fortification of bread flour has influenced colorectal cancer incidence in Australia.