EVIDENCE FOR DIMINISHED B-12 ABSORPTION AFTER GASTRIC BYPASS - ORAL SUPPLEMENTATION DOES NOT PREVENT LOW PLASMA B-12 LEVELS IN BYPASS PATIENTS

Vitamin and mineral assays were performed on blood in 20 gastric bypass patients preoperatively and 6 and 12 months postoperatively. Values were compared with serial food records in nine patients. Postoperatively, all patients were prescribed a supplement containing the recommended dietary allowances (RDA) for vitamins and minerals. Weight, calorie and protein intake, and total serum protein decreased over the study interval (p < 0.0 1). Dietary intakes of vitamins B1, B2, B6, folate, iron and zinc fell (p < 0.01), but total intake (i.e., diet + supplement) did not decrease with the exception of iron. Blood indicators of these nutrients were normal preoperatively and did not decline. However, plasma vitamin B-12 levels decreased from 385 pg/ml preoperatively to 234 pg/ml at 1 year (p = 0.0064), despite an increase in total vitamin B-12 intake from 2.6 to 11.7-mu-g/day (p = 0.1173). Five patients (27.8%) had abnormally low plasma vitamin B-12 levels at 1 year postoperatively; four were taking at least the RDA for vitamin B-12 as supplements. Although oral supplementation containing the RDA for micronutrients can prevent abnormal blood indicators of most vitamins and minerals, it is insufficient to maintain normal plasma B-12 levels in about 30% of gastric bypass patients.