Diagnose and treatment of functional vitamin B12 deficiency after bariatric surgery

A low vitamin B12 level (< 140 pmol/l) is common after bariatric surgery, and in general treated with vitamin B12 supplementation. Serum vitamin B12 level is a poor predictor of functional vitamin B12 status, since clinical symptoms of a deficiency also occurs at vitamin B12 levels above 140 pmol/l. Methyl Malonic Acid (MMA) is a more sensitive and specific parameter for a functional vitamin B12 deficiency In order to determine whether the current supplementation strategy is correct, the effect of vitamin B12 supplementation on clinical symptoms, vitamin B12 and MMA levels is determined in patient with serum B12 levels of 140-200 pmol/l.

45 Bariatric patients with serum vitamin B12 levels between 140 and 200 pmol/l received intra-muscular hydroxocobalamin injections, the control group not (n=45). Difference in MMA in both groups were tested with a Chi-square test. Significance of the difference between subgroups were determinated by the independent t-test and Mann-Whitney U-test. A paired t-test was used to test the vitamin B12 values, MMA and clinical complaints in both groups at the start and during follow-up. Results were significant at p < 0,05.

At baseline, 36% of the supplemented patients had a MMA level > 300 nmol/L. These patients showed a significant increase in vitamin B12 levels from 176 ± 27,5 to 1068 ± 435 (p<0,001) and a significance decrease of MMA levels from 413 ± 259 to 129 ± 40 (p<0,001). Vitamin B12 values in the control group were constant: from 177 ± 18 to 178 ± 30 (p=0,7). MMA values increased significant in controls from 228 ± 66 to 323 ± 136 (p<0,001). At the start 29% of the patients from the intervention group and 18% of the controls had clinical symptoms of a deficiency. These symptoms disappeared in all patients of the supplementation group, against no improvement in the group without supplementation.

This study shows that all bariatric patients with vitamin B12 levels between 140 and 200 pmol/L benefit from vitamin B12 supplementation, both in clinical and biochemical outcomes.