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Folate Supplements and the Masking of Vitamin B-12 Deficiency

Human Nutritional Sciences Department, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada

Dear Sir:

I wish to comment on the title of the article "The Chilean Flour Folic Acid Fortification Program Reduces Serum Homocysteine Levels and Masks Vitamin B-12 Deficiency in Elderly People" (1 ). The authors measured hematological data and plasma vitamin B-12 levels in 108 elderly before and after a food fortification program with folate (220 µg/100 g flour). After 6 mo there was no change in either hemoglobin or hematocrit with a slight change in MCV. Vitamin B-12 levels remained unchanged. This study of food fortification has merit; however, the authors did not study the masking of vitamin B-12 deficiency in elderly people.

Based on their data, the authors concluded that "neurological and hematological alterations could appear in the future." The slight increase in MCV "even within normal range is probably an indicator of ongoing cobalamin deficiency." These data are not evidence of a masking of vitamin B-12 deficiency but rather speculation that it might occur. In fact, there are no data from any food fortification trial to support the hypothesis that folate supplementation masks vitamin B-12 deficiency. There are data that show large doses of folate (5–50 mg; note, not micrograms) over prolonged periods could confuse interpretation of B-12 metabolism and in some patients, not all, be associated, not cause, progression of neurological progression (2 ). Their progression was most likely attributable to the absence of appropriate vitamin B-12 therapy, not treatment with folate. Most important, there are absolutely no data to show that folate supplements cause B-12 deficiency.

Why are these important distinctions? In Canada we are trying to decide whether to add folate to more products to match what is currently done in the United States. Because there has been a welcome drop in neural tube defects in our province and across the country (Wayne Andrews, Memorial University of Newfoundland, 2002, personal communication), the possible benefits of increased folate fortification are being examined. We are concerned that data such as this be misinterpreted as a "masking" of B-12 deficiency and lead to confusion about the more important benefits that would arise from current folate fortification. It is much more reasonable, as the authors suggest, to add B-12 to flour and even to increase food folate above current levels (3 ).

Manuscript received 18 April 2002. Initial review completed 18 April 2002. Revision accepted 19 April 2002.

LITERATURE CITED

1. Hirsch, S., de La Maza, P., Barrera, G., Gattas, V., Petermann, M. & Bunout, D. (2002) The Chilean flour folic acid fortification program reduces serum homocysteine levels and masks vitamin B-12 deficiency in elderly people. J. Nutr. 132:289-291.[Abstract/Free Full Text]

2. Schwartz, S. O., Kaplan, S. R. & Armstrong, B. E. (1950) The long-term evaluation of folic acid in the treatment of pernicious anemia. J. Lab. Clin. Med. 35:894-898.

3. Oakley, G. P., Jr. (1997) Let’s increase folic acid fortification and include vitamin. Am. J. Clin. Nutr. 65:1889-1890.[Free Full Text]

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