Effect of gastric bypass surgery on vitamin D nutritional status.

BACKGROUND: We previously reported a 60% prevalence of vitamin D (VitD) depletion, defined as a 25-hydroxyvitamin D (25-OHD) level of < or =20 ng/mL, in morbidly obese patients preoperatively. We now report the effect of gastric bypass (GB) on the VitD nutritional status in these patients.

METHODS: We prospectively studied 108 morbidly obese patients who had undergone GB. Routine postoperative supplementation consisted of 800 IU VitD and 1500 mg calcium daily. Serum calcium, parathyroid hormone, and 25-OHD were measured before and 1 year after GB.

RESULTS: The mean patient age was 46 +/- 9 years, 93% were women, and 72% were white. Preoperatively and at 1 year postoperatively, the prevalence of VitD depletion and hyperparathyroidism (HPT) and the mean 25-OHD level was 53% and 44%, 47% and 39%, and 20 and 24 ng/mL, respectively. One year after GB, the percentage of excess weight loss was 67% and demonstrated significant correlations both positively with 25-OHD and inversely with parathyroid hormone. At both intervals, blacks had a greater incidence of VitD depletion than did whites, and, at 1 year after GB, HPT was more common in patients with VitD depletion (55% versus 26%, P = .002).

CONCLUSION: With customary supplementation, VitD nutrition is improved after GB, but VitD depletion persists in almost one half of patients, and blacks are at a significantly greater risk than whites. HPT did not improve, and those with VitD depletion had a significantly greater rate of HPT. Additional prospective studies are needed to determine how to optimize VitD nutrition and avoid potential long-term skeletal complications after GB.