Declining Rate of Folate Insufficiency among Adults Following Increased Folic Acid Food Fortification in Canada

Article excerpt

ABSTRACT

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 1312 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 Q.

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% Cl 0.14-0.40). No significant difference was observed between periods in the prevalence of B1 2 insufficiency below 120 pmol/L (3.93% versus 3.11 %, respectively; RR 0.79, 95% Cl 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 1312 insufficiency, including identifying the benefits of folic acid food fortification and the need to further consider fortification or supplementation with vitamin B12.

A Canadian national program was mandated in November 1998 to ncrease folic acid fortification of all flour and some corn and rice products, providing a daily average of 0.1 mg of folic acid. The goal of this initiative was to provide women of reproductive age with higher amounts of dietary folic acid in order to reduce the risk of neural tube defects.1

Since the introduction of this program, we expected that there would be a rise in both the average serum (Se) and red cell (RBC) folate concentrations, but we could not predict what would happen with serum vitamin B12 (Se B12).2 Since vitamin B12 impairment might be more difficult to recognize in the presence of adequate folate stores, this might have widespread public health importance for Canadians.2 In the following report, we examined whether there has been a change in both vitamins within the adult population since this program was implemented.

Data collection

We retrospectively analyzed all consecutive, concomitant and non-redundant serum folate, RBC folate and Se B12 samples previously measured by MDS Laboratories (Toronto, Ontario), a large private laboratory that completes testing on approximately 30% of all B12 and folate measurements across the province of Ontario, paid for under the universal Ontario Health Insurance Plan. Samples were collected from 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) (Table I). Period B reflected a six-month interval spanning industry-compliance lead and lag times of three months each. The underlying reasons for folate and Se B12 testing were not available, but each patient's physician ordered the sample on clinical grounds. RBC folate, Se folate and Se B12 were measured by competitive protein binding (Bio-Rad Laboratories, Mississauga, Ontario). The maximum reporting limit was 45 nmol/L for Se folate, 1450 nmol/L for RBC folate and 1600 pmol/L for Se 12. The laboratory coefficient of variation (CV) was less than 7% for each of the three assays. Patient identifiers were removed to ensure patient confidentiality, and ethical approval to conduct this study was obtained by the Institutional Review Board of Sunnybrook and Women's College Health Sciences Centre. …