Persistence of vitamin B12 insufficiency among elderly women after folic acid food fortification.

OBJECTIVE: To estimate the associated risk of folate and vitamin B12 (B12) insufficiency, as well as vitamin repletion, following folic acid food fortification. DESIGN: Retrospective cross-sectional study over a 5-year period. SETTING: Two large laboratory databases in the provinces of Ontario and British Columbia, Canada. PARTICIPANTS: 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). MEASUREMENTS: 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). RESULTS: 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 < 0.001). The average B12 concentration increased from 280 to 300 pmol/L, which was more pronounced in BC (p < 0.001) than in Ontario (p = 0.16). The prevalence of folate deficiency declined from 6.3% to 0.88% after fortification (PR 0.14, 95% confidence interval [CI] 0.11-0.18), while the decline in B12 deficiency was less pronounced (PR 0.78, 95% CI 0.71-0.86). CONCLUSIONS: The prevalence of combined B12 insufficiency with supraphysiological concentrations of serum folate increased from 0.09% pre-fortification to 0.61% post (PR 7.0, 95% CI 2.6-19.2). The introduction of folic acid food fortification was associated with a substantial improvement in the folate status of Canadian women aged 65 years and older, paralleled by a large decline in the rate of folate deficiency. Improvement in the B12 status of these women was far less pronounced. Because the prevalence of combined B12 insufficiency and supraphysiological concentrations of serum folate may have increased with folic acid food fortification, consideration should be given to confirming this finding, and possibly, to the addition of B12 to folate fortified foods.

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.

An Ontario-wide study of vitamin B12, serum folate, and red cell folate levels in relation to plasma homocysteine: is a preventable public health issue on the rise?.

BACKGROUND: Plasma homocysteine has been reported to be useful in the evaluation of patients with suspected vitamin B12 or folate deficiency. In November 1998, Canada began its mandatory fortification of all flour, and some corn and rice products, with folic acid. We evaluated the status of folate and vitamin B12 in Ontario since this fortification program began, and also studied the role of plasma homocysteine in the assessment of vitamin B12 deficiency since that time. METHODS: A retrospective cross-sectional study design was performed using a community database of all Ontario samples analyzed by MDS Laboratories, a major provider of diagnostic laboratory services in Canada. All consecutive single-patient fasting samples for plasma homocysteine collected between January 1 and September 30, 1999 were included, as well as corresponding red cell folate and serum B12 concentrations. Data for serum folate were included when available. Descriptive statistics included the arithmetic and geometric means for each measure, as well as the lower and upper centile values. After excluding cases with a concomitant serum creatinine > 120 micromol/L or red cell folate < 215 nmol/L, we established the test properties of a plasma homocyteine level of 15 micromol/L or greater for the diagnosis of "low" (< 120 pmol/L) or "indeterminate" (i.e., between 120 and 150 pmol/L) serum vitamin B12 concentrations. RESULTS: The mean age of all subjects was 58.4 years (95% CI 57.4 to 59.4). Plasma homocysteine samples were obtained from 403 males (56.7%) and 308 females. The geometric mean homocysteine concentration for the entire population was 8.3 micromol/L, and was significantly higher among males (9.3 micromol/L) than females (8.3 micromol/L) (unpaired t-test: 2-p < 0.0001). The geometric mean serum folate concentration was significantly higher in females (35.8 nmol/L) than males (33.6 nmol/L) (2-p < 0.0001), as were the mean red cell folate levels (females 966.8 nmol/L, males 949.3 nmol/L; 2-p < 0.0001). Serum vitamin B12 concentrations were available for 692 subjects, with a geometric mean of 322.0 pmol/L. Again, mean vitamin B12 was higher in females (332.5 pmol/L) than males (314.3 pmol/L) (2-p < 0.0001). The fifth centile for vitamin B12 was 134.6 pmol/L. A plasma homocysteine concentration > 15 micromol/L did not discriminate between cobalamin concentrations below versus above 120 pmol/L (positive and negative predictive values 7.4% and 97.2%, respectively), nor did it discriminate "indeterminate" B12 levels between 120 and 150 pmol/L (positive and negative predictive values 6.3% and 94.0%, respectively). CONCLUSION: In a large select group of Ontarians, serum and red cell folate concentrations appear to be higher than expected, possibly due to a recent national folate fortification programme; cobalamin levels are no higher than expected. Given our inability to detect mild B12 deficiency using such indicators as plasma homocysteine, and considering the substantial growth in the elderly segment of the Canadian population, occult cobalamin deficiency could become a common disorder. Accordingly, we recommend either consideration of the addition of vitamin B12 to the current folate fortification programme, and/or the development of better methods for the detection of cobalamin deficiency.