Predicting iron absorption from an effervescent iron supplement in obese patients before and after Roux-en-Y gastric bypass: a preliminary study.

BACKGROUND & AIMS: Oral iron absorption is hampered in obese and bariatric patients, especially after Roux-en-Y gastric bypass (RYGB). As a result, iron deficiency, which is common in both patient groups, can be difficult to treat by oral supplements, often necessitating a switch to parenteral administration. The aim of this study was to find possible predictors of the extent of absorption of an effervescent iron gluconate oral supplement, which enables to pre-emptively identify those patients in which oral supplementation is likely to fail. METHODS: The pharmacokinetic properties of 695 mg effervescent iron gluconate (80 mg Fe2+) were assessed in 13 obese patients (female = 10; mean age ± SD: 45.2 ± 12.5years) pre- and six months post-RYGB by measuring serum iron concentrations during 24 hours and by calculating the adjusted for baseline AUC0-24h, Cmax and Tmax. A multivariate regression analysis was performed to investigate the effect of hepcidin concentration, iron and hematologic indices, personal and anthropometric characteristics on iron absorption. Subsequently, Receiver Operating Characteristic (ROC) curves were used to propose the cut-off value for hepcidin concentrations above which obese patients are unlikely to benefit from oral iron supplementation. Data are expressed as mean ± SD. RESULTS: Low iron status persisted after surgery as there was no significant difference observed in TSAT (17.3 ± 5.2 vs. 20.2 ± 6.6%), ferritin (91.8 ± 68.6 vs. 136.2 ± 176.9 µg/L) and hepcidin concentration (32.0 ± 30.1 vs. 28.3 ± 21.3 ng/mL) after RYGB. The absorption of effervescent iron gluconate was similar pre- and post-RYGB [AUC0-24h,pre-RYGB: 28.6 ± 10.8 µg/dL*h; AUC0-24h,post-RYGB: 27.5 ± 9.11 µg/dL*h (P = 0.84)]. Post-RYGB, iron AUC0-24h showed a strong negative correlation with both hepcidin concentrations and TSAT (R=-0.51; P = 0.08 and R=-0.81; P = 0.001), respectively. Pre-RYGB, there was a clear trend for the same negative correlations for hepcidin concentrations and TSAT (R=-0.47; P = 0.11 ;R=-0.41; P = 0.16), respectively. Taking pre-and post-RYGB data together, the negative correlations were confirmed for hepcidin concentrations and TSAT (R=-0.54; P = 0.004; R=-0.60; P = 0.001), respectively. The AUCROC = 0.87 (95%CI 0.71; 1.00) showed an optimal sensitivity/specificity cut-off at hepcidin concentrations of 26.8 ng/mL. CONCLUSIONS: The iron AUC0-24h showed a negative correlation with the hepcidin concentration and TSAT of obese patients, in particular post-RYGB. Therefore, our data support the use of hepcidin concentration and TSAT to distinguish potential responders from non-responders for iron supplementation particularly post-RYGB. Additionally, this study showed that the pharmacokinetic properties of iron gluconate from an effervescent tablet were unaffected by RYGB-surgery.

The relevance of dietary protein after bariatric surgery: what do we know?

PURPOSE OF REVIEW: The growing obesity epidemic is associated with an increased demand for bariatric surgery with Roux-en-Y Gastric Bypass and Sleeve Gastrectomy as the most widely performed procedures. Despite beneficial consequences, nutritional complications may arise because of anatomical and physiological changes of the gastrointestinal tract. The purpose of this review is to provide an update of the recent additions to our understanding of the impact of bariatric surgery on the intake, digestion and absorption of dietary protein. RECENT FINDINGS: After bariatric surgery, protein intake is compromised because of reduced gastric capacity and aversion for certain foods. A minority of patients reaches the recommended protein intake of minimal 60 g per day, which results in the loss of fat-free mass rather than the desired loss of fat mass. Despite inadequate protein intake, protein digestion and absorption do not seem to be impaired suggesting that other mechanisms could counteract the reduced secretion of digestive enzymes and their delayed inlet. SUMMARY: After bariatric surgery, protein supplementation or diet enrichment could attribute to achieve the minimal recommended protein intake and benefit the amount and composition of postoperative weight loss.

Micronutrient intake, from diet and supplements, and association with status markers in pre- and post-RYGB patients.

BACKGROUND & AIMS: Roux-en-Y gastric bypass (RYGB) is associated with an increased risk for micronutrient deficiencies. This study aimed to assess total (dietary and supplement) intake and association with iron (including hepcidin), vitamin B12, vitamin C and zinc status markers before and after Roux-en-Y gastric bypass (RYGB). METHODS: This prospective study included patients with a planned RYGB in University Hospitals Leuven, Belgium; who were followed until 12 months post-RYGB. Patients completed an estimated dietary record of two non-consecutive days before and 1, 3, 6 and 12 months post-RYGB and supplement/drug use was registered. Associations between total micronutrient intake and status markers were analyzed. RESULTS: Fifty-four patients (21 males; mean age: 48.0 [95%CI 46.6; 49.3] years; mean preoperative BMI: 40.4 [95%CI 39.4; 41.4] kg/m2) were included. One month post-RYGB, usual dietary intake of the studied micronutrients was significantly decreased compared to pre-RYGB, but gradually increased until 12 months post-RYGB, remaining below baseline values. By including micronutrient supplement intake, 12 months post-RYGB values were higher than baseline, except for zinc. Hemoglobin, ferritin, vitamin B12 and C-reactive protein serum concentrations were significantly decreased and transferrin saturation and mean corpuscular volume were significantly increased 12 months post-RYGB. Serum hepcidin concentration was significantly decreased 6 months post-RYGB. CONCLUSIONS: Medical nutritional therapy is essential following RYGB as dietary intake of iron, vitamin B12, vitamin C, copper and zinc was markedly decreased postoperatively and some patients still had an inadequate total intake one year post-RYGB.

Iron deficiency after Roux-en-Y gastric bypass: insufficient iron absorption from oral iron supplements.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) may reduce the absorption of iron, but the extent to which this absorption is impeded is largely unknown. First, we determined the prevalence of iron deficiency following RYGB and explored the risk factors for its development. Second, we examined to what extent oral iron supplements are absorbed after RYGB. METHODS: Monocentric retrospective study in 164 patients (123 females, 41 males; mean age 43 years) who underwent RYGB between January 2006 and November 2010 was done. Pre- and postoperative data on gender, age, BMI, serum levels of iron, ferritin, hemoglobin, vitamin B12, 25-hydroxy vitamin D, and use of proton pump inhibitors and H2 antagonists were collected. Generalized linear mixed models were used for the analysis of the data. In 23 patients who developed iron deficiency after surgery, an oral challenge test with 100 mg FeSO4 · 7H2O was performed. RESULTS: Following RYGB, 52 (42.3 %) female patients and 9 male (22.0 %) patients developed iron deficiency (serum ferritin concentration ≤ 20 µg/L). The prevalence of iron deficiency was significantly higher in females than males (p = 0.0170). Young age (p = 0.0120), poor preoperative iron status (p = 0.0004), vitamin B12 deficiency (p = 0.0009), and increasing time after surgery (p < 0.0001) were also associated with iron deficiency. In the oral iron challenge test, only one patient out of 23 showed sufficient iron absorption. CONCLUSIONS: Iron deficiency is extremely frequent after RYGB and is linked with different risk factors. Iron supplementation seems essential, but the effect of oral tablets may be limited as absorption of oral iron supplements is insufficient post-RYGB.