A randomized, double-blind, placebo-controlled study of oral vitamin B12 supplementation in older patients with subnormal or borderline serum vitamin B12 concentrations.

OBJECTIVES: To determine the effect of small doses of oral cyanocobalamin supplements in older patients with low or borderline serum vitamin B12 concentrations but no other evidence of pernicious anemia (PA).

DESIGN: Randomized, double-blind, placebo-controlled study assessing the efficacy of oral cyanocobalamin 10 microg and 50 microg daily for 1 month.

SETTING: Two geriatric hospitals in the North Western Health Care Network, Melbourne, Australia.

PARTICIPANTS: Thirty-one inpatients with serum vitamin B12 levels between 100 and 150 pmol/L, without PA, other malabsorption disorders, or progressive neurological or terminal illness. The mean age was 81.4 years.

INTERVENTION: After informed consent, a medical and drug history was taken and the Mini-Mental State Examination (MMSE) completed. A dietitian made assessment of oral cobalamin intake. Blood was taken for serum vitamin B12, serum and red cell folate assay, full blood examination, fasting serum gastrin, parietal and intrinsic factor antibodies, fasting serum homocysteine, and creatinine. Patients were then randomized to receive 10 microg oral cyanocobalamin, 50 microg oral cyanocobalamin, or placebo treatment for 1 month, after which the investigations and clinical examinations were repeated.

MEASUREMENTS: Percentage change in the level of vitamin B12, homocysteine, folate, and red cell parameters and absolute changes in MMSE were calculated and compared between groups. The groups were compared on the number of responders who improved their level of B12 by 20%. Chi-square calculations on changes in serum vitamin B12 concentration were also performed.

RESULTS: Mean serum vitamin B12 +/- standard deviation improved by 51.7 +/- 47.1% in the 50-microg group, 40.2 +/- 34.4% in the 10-microg group, and 11.7 +/- 24.5% in the placebo group. The change in the 50-microg cyanocobalamin group was significantly greater than that in the placebo group (P=.044). The change in the 10-microg cyanocobalamin group was not significantly different from that in the placebo group (P=.186). Eight of 10 subjects in each treatment group were classified as responders, compared with two of 11 in the placebo group (P=.004). Homocysteine levels fell in patients receiving cyanocobalamin, but this fall failed to reach statistical significance. There were no significant changes in the other parameters measured.

CONCLUSION: Cyanocobalamin supplementation of 50 microg but not 10 microg daily produced a significant increase in serum vitamin B12. This result has implications for the management of patients with subnormal or borderline serum vitamin B12 concentrations and for food fortification with vitamin B12.