To estimate the associated risk of folate and vitamin B12 (B12) insufficiency, as well as vitamin repletion, following folic acid food fortification.
Retrospective cross-sectional study over a 5-year period.
Two large laboratory databases in the provinces of Ontario and British Columbia, Canada.
Canadian women aged 65 years and over who underwent concomitant clinical testing of serum folate and B12 during the pre-fortification period of January 1996 to December 1997 in Ontario (n = 733) and British Columbia (n = 3839), and in the near-complete post-fortification period of January 1998 to December 2000 in Ontario (n = 4415) and British Columbia (n = 6677).
Geometric mean concentrations of serum folate and B12 before and after folate fortification. Prevalence ratios (PR) were used to separately compare the post- and pre-fortification period rates of folate deficiency (below 6.0 nmol/L); B12 insufficiency (below 150 pmol/L); and B12 insufficiency in combination with supraphysiological concentrations of serum folate (above 45 nmol/L).
The mean baseline folate and B12 concentrations were similar between provinces. Using the combined provincial data, the mean serum folate concentration increased by 64% after fortification, from 14.8 to 24.2 nmol/L (p