Declining rate of folate insufficiency among adults following increased folic acid food fortification in Canada.

Objective: Canada introduced a mandatory folic acid food fortification program in November 1998. We investigated whether the rate of folate and vitamin B12 insufficiency among adults has changed since this mandatory fortification program was implemented.
Methods: We conducted a retrospective cross-sectional study using a large Ontario laboratory database. We included all individuals who underwent evaluation of their serum folate, red cell folate and serum vitamin B12 between April 1, 1997 to July 31, 1998 (Period A), August 1, 1998 to January 30, 1999 (Period B) and February 1, 1999 to March 31, 2000 (Period C).
Results: A total of 8,884 consecutive samples were analyzed during the period of study. Mean age was 57.4 years (SD 21.1), and 63.2% were female. The prevalence of serum folate insufficiency (below 3.4 nmol/L) fell from 0.52% in Period A to 0.22% in Period C [prevalence ratio (RR) 0.41, 95% confidence interval (CI) 0.18-0.93)]. The prevalence of red cell folate insufficiency (below 215 nmol/L) declined from 1.78% during Period A to 0.41% in Period C (RR 0.23, 95% CI 0.14-0.40). No significant difference was observed between periods in the prevalence of B12 insufficiency below 120 pmol/L (3.93% versus 3.11%, respectively; RR 0.79, 95% CI 0.62-1.01).
Conclusions: There has been a significant decline in the prevalence of folate, but not vitamin B12 insufficiency, following Canadian folic acid food fortification. These changes may have important implications for the prevention and detection of folate and vitamin B12 insufficiency, including identifying the benefits of folic acid food fortification and the need to further consider fortification or supplementation with vitamin B12.