BACKGROUND: Concerns regarding nutritional deficiencies have recently emerged after Roux-en-Y gastric bypass (RYGB).

METHODS: A total of 835 subjects underwent RYGB, age 43.3 years, body mass index (BMI) 47.2 kg/m(2). Hematological and calcium metabolic variables were measured before, 6, 12, and 24 months after surgery. Daily supplement of 800 mg calcium, 800 U vitamin D, a multivitamin, and a vitamin B12 injection (1 mg) every third month was recommended. In subjects with low ferritin and decreasing hemoglobin levels, oral, or intravenous iron was administered.

RESULTS: Hemoglobin concentration decreased from before surgery to month 24 for both men (9.3 ± 0.05 vs. 8.3 ± 0.08 mmol/L, p < 0.001) and women (8.4 ± 0.03 vs. 7.7 ± 0.06 mmol/L, p < 0.001). At 24 months, anemia was present in 25.8 % of women and 22.1 % of men. Predictors of anemia in both sexes were baseline hemoglobin (p < 0.001), excessive weight loss in men, and younger age in women (p < 0.001). Plasma ferritin levels decreased in both sexes (p < 0.01), whereas concentrations of folic acid and vitamin B12 increased from before surgery to 24 months after surgery (p < 0.001). Vitamin D increased from baseline to month 24 in both sexes (p < 0.01). In women, PTH increased from baseline to month 24 (p < 0.05) with no changes in calcium or magnesium.

CONCLUSIONS: Supplementation of calcium and vitamin D was sufficient. Iron substitution did not prevent anemia, which especially affected premenopausal women. More attention should be given to iron substitution after RYGB.