Bone and Gastric Bypass Surgery: Effects of Dietary Calcium and Vitamin D

Goode LR, Brolin RE, Chowdhury HA and Shapse SA Obes Res. 2004;12:40-47.

Objective

To examine bone mass and metabolism in women who had previously undergone Roux-en-Y gastric bypass (RYGB) for morbid obesity and to examine the effect of supplementation with calcium and vitamin D.

Methods

Forty-four women who had undergone RYGB for morbid obesity were recruited to undergo bone density screening using DXA. Bone mineral density and bone mineral content (BMC) were examined in the women and compared with age- and weight- matched control (CNT) women (n=65). In a separate analysis, RYGB women who presented with low bone mass (n=13) were randomly assigned to receive 600 mg/d elemental calcium either as a tablet or in the form of a meal replacement shake and meal bar (Slim-Fast); all subjects received 5 ug vitamin D and 160 mg/day of Ca in the form of a multivitamin and mineral supplement over six months and were compared with an unsupplemented CNT group (n=13). Bone mass and turnover and serum parathyroid hormone (PTH) and 25-hydroxyvitamin D were measured.

Results

Bone mass did not differ between premenopausal RYGB and CNT women, whereas postmenopausal RYGB women had higher bone mineral density and BMC at the lumbar spine and lower BMC at the femoral neck. Before and after dietary supplementation, bone mass was similar, and serum PTH and markers of bone resorption were higher in RYGB compared with CNT women and did not change significantly after supplementation.

Conclusion

Postmenopausal RYGB women show evidence of secondary hyperparathyroidism, elevated bone resorption, and patterns of bone loss similar to other subjects with hyperparathyroidism. Although a modest increase in Ca or vitamin D does not suppress PTH or bone resorption, it is possible that greater dietary supplementation may be beneficial.

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