BMJ  2004;328:769 (27 March), doi:10.1136/bmj.328.7442.769

Letter

Folic acid as ultimate in disease prevention

Beware of vitamin B12 deficiency

EDITOR—In response to the review by Lucock on folic acid supplementation,¹ we have a word of caution about possible concomitant vitamin B12 deficiency, which may also cause raised concentrations of homocysteine.

Vitamin B12 deficiency can be subtle, manifesting only as an increase in concentrations of homocysteine and methylmalonic acid in blood and urine, with concentrations of vitamin B12 at the lower limit of normal.² Vitamin B12 concentration varies in different populations. The US NHANES III survey found a mean serum B12 value of 518 pg/ml, and 3% of the population had a concentration of less than 200 pg/ml.³ In Israel we reported a vitamin B12 deficiency of 30% in 130 serial patients undergoing coronary angiography.⁴ Health maintenance organisations in Israel responded to the widespread deficiency of vitamin B12 by lowering the normal values of their laboratories.

Since folic acid supplementation may be harmful in the presence of undiagnosed vitamin B12 deficiency, we recommend that vitamin B12 concentrations be determined before administration of folic acid. Another approach may be to use multivitamin tablets. The use of a "folate" supplement consisting of 1 mg folic acid, 400 µg vitamin B12, and 10 mg pyridoxine both reduces the concentrations of homocysteine and decreases the rate of restenosis after angioplasty.⁵ The cost effectiveness of these approaches may differ from country to country, depending on the prevalence of vitamin B12 deficiency.

Kaplan Medical Centre, Rehovot 76100, Israel stevash{at}tredline.co.il

department of internal medicine C, heart institute, Kaplan Medical Centre, Rehovot 76100, Israel stevash{at}tredline.co.il

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Competing interests: None declared.

References

1. Lucock M. Is folic acid the ultimate functional food component for disease prevention? BMJ 2004;328: 211-4. (24 January.)[Free Full Text]
2. Green R. Metabolite assays in cobalamin and folate deficiencies. Ballière's Clin Hematol 1995;8: 533-66.
3. Wright JD, Bialostosky K, Gunter EW, Carroll MD, Najjar MF, Bowman BA, et al. Blood folate and vitamin B12: United States, 1988-94. Vital Health Stat 1998;243: 1-78.
4. Goland S, Ayzenberg O, Kuznitz F, Shimoni S, Caspi A, Malnick S. A high incidence of Vitamin B12 deficiency in Israeli patients undergoing coronary angiography. Cardiovasc Drug Ther 2003;17: 191.[CrossRef][ISI][Medline]
5. Schnyder G, Roffi M, Pin R, Hess OM. Decreased rate of coronary restenosis after lowering of plasma homocysteine levels. N Engl J Med 2001;345: 1593-600.[Abstract/Free Full Text]

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