Comparison of the Absorption of Calcium Citrate and Calcium Carbonate in Patients With an RYGB, LSG, and OAGB A Double-blind, Randomized Cross-over Trial

Calcium, predominantly absorbed in the duodenum and proximal jejunum, relies heavily on vitamin D and an acidic environment to facilitate absorption. With the increasing prevalence of bariatric metabolic surgery (BMS) procedures and their malabsorptive effects, the likelihood of fat-soluble vitamin malabsorption becomes heightened. This stems from bypassing the stomach, key absorption sites in the intestine, and the inefficient mixing of bile salts.

BMS is often associated with several bone metabolism disorders, including the acceleration of bone remodeling and turnover, bone loss, and decreased bone mineral density (BMD). Postoperative calcium supplementation can mitigate this bone loss over time. For instance, a study demonstrated the beneficial effect of calcium citrate following Roux-en-Y gastric bypass (RYGB). However, the study's statistical power was insufficient; thus, the BMS field still awaits further conclusive and robust research to establish definitive guidelines, which was highlighted in another study.

Moreover, substantial changes in gut hormones, such as peptide YY (PYY), glucagon-like peptide-1, and ghrelin, have been observed following RYGB, sleeve gastrectomy (SG), and One Anastomosis Gastric Bypass (OAGB). While these hormonal changes are typically associated with BMS's numerous positive metabolic benefits, they may also contribute to bone loss.

Consequently, the precise impact of calcium absorption in relation to RYGB, SG, and OAGB remains under-researched in terms of statistical power and the diversity of BMS procedures considered. Therefore, this presents a critical area for future investigation to improve patient outcomes in BMS.