Comparison of the absorption of calcium carbonate and calcium citrate after Roux-en-Y gastric bypass

Abstract

Introduction: Roux-en-Y gastric bypass (RYGB) restricts food intake. Consequently, patients consume less calcium. In addition, food no longer passes through the duodenum, the main site of calcium absorption. Therefore, calcium absorption is significantly impaired. The goal of this study is to compare two common calcium supplements in gastric bypass patients.

Method: Nineteen patients were enrolled in a randomized, double-blinded, crossover study comparing the absorption of calcium from calcium carbonate and calcium citrate salts. Serum and urine calcium levels were assessed for peak values (C (max)) and cumulative calcium increment (area under the curve [AUC]). Serum PTH was assessed for minimum values (PTH(min)) and cumulative PTH decrement (AUC). Statistical analysis was performed using a repeated analysis of variance model.

Results: Eighteen subjects completed the study. Calcium citrate resulted in a significantly higher serum C (max) (9.4 + 0.4 mg/dl vs. 9.2 + 0.3 mg/dl, p = 0.02) and serum AUC (55 + 2 mg/dl vs. 54 + 2 mg/dl, p = 0.02). Calcium citrate resulted in a significantly lower PTH(min) (24 + 11 pg/ml vs. 30 + 13 pg/ml, p = 0.01) and a higher AUC (-32 + 51 pg/ml vs. -3 + 56 pg/ml, p = 0.04). There was a non-significant trend for higher urinary AUC in the calcium citrate group (76.13 + 36.39 mg/6 h vs. 66.04 + 40.82, p = 0.17).

Conclusion: Calcium citrate has superior bioavailability than calcium carbonate in RYGB patients.

Figures

Fig. 1

Serum calcium. a Data are presented as mean and standard deviation. The omnibus difference between the calcium supplements were statistically significant (p<0.0001, repeated measures analysis). Filled circles p<0.05, **p<0.01 vs. time 0; †p<0.001 vs. calcium carbonate. b Symbols and lines represent individual subjects. Solid bars indicate the mean ΔAUC of each phase

Fig. 2

Serum PTH. a Data are presented as mean and standard deviation. The omnibus difference between the calcium supplements were statistically significant (p<0.0001, repeated measures analysis). *p<0.05, **p<0.01 vs. time 0; (*)p<0.05, (**)p<0.01, (†) p<0.001 vs. calcium carbonate. b Symbols and lines represent individual subjects. Solid bars indicate the mean ΔAUC of each phase

Fig. 3

Urine calcium. a Data are presented as geometric mean and 95% confidence interval. *p=0.001 compared Time 0 within phase, (†)p=0.01 compared to calcium carbonate. The response differences over time between the calcium supplements were statistically significant (p=0.03, supplement by hour interaction). b Symbols and lines represent individual subjects. Solid bars indicate the mean ΔAUC of each phase

Fig. 4

Urine calcium/creatinine. a Data are presented as geometric mean and 95% confidence interval. *p<0.05 vs. Time 0; (†)p=0.007 vs. calcium carbonate. The response differences over time between the calcium supplements were statistically significant (p=0.001, supplement by hour interaction). b Symbols and lines represent individual subjects. Solid bars indicate the mean ΔAUC of each phase