The vitamin E, vitamin B-6, vitamin B-12, and folate status of 22 gastric bypass subjects ages 23 to 60 yr was evaluated before, 6 mo, and 12 mo post-surgery. Before surgery 77.3% of subjects had adequate vitamin E status; 36.3%, adequate vitamin B-6 status; 100.0%, adequate vitamin B-12 status; and 45.5%, adequate folate status. After surgery, subjects were classified into 3 vitamin supplement groups based on average daily vitamin supplement intake. Subjects taking higher levels of supplements containing these vitamins had significantly higher plasma concentrations of the vitamins than those taking low or moderate levels. The mean plasma vitamin values in the moderate supplement group were indicative of adequate status for all vitamins, but plasma vitamin B-12 levels at 12 mo post-surgery were significantly lower than pre-surgery levels. In the low supplement group, mean plasma vitamin levels were in or near marginal or deficient range. The majority of subjects consuming supplements of vitamin E, vitamin B-6, and folate near the US RDA maintained normal vitamin status. Subjects taking 100+ ug vitamin B-12 daily had adequate vitamin B-12 status. Significant correlations (r = .67 to .94) were observed between vitamin supplement levels and the respective plasma vitamin concentrations. / Ph. D. / incomplete_metadata