The influence of diet and oral iron supplementation on iron status after gastric bypass surgery

Renee A Mischler, Purdue University

Abstract

The percentage of US adults in the subcategory of severe obesity, with a body mass index (BMI) > 40 kg/m2, has overwhelmingly increased in the past decade. Because severe obesity is such a major public health concern, bariatric surgery is and will continue to be popular in the United States. Bariatric surgery is an effective way for severely obese patients to lose a significant amount of weight; however, the benefits are mitigated by a high prevalence of iron deficiency, which has been documented to occur in as high as 60% of patients after surgery. A variety of factors exist which contribute to iron deficiency after bariatric surgery. A few examples include decreased dietary intake of bioavailable heme iron, decreased dietary intake of total iron, and reduced intestinal iron absorption. Considering the multitude of factors contributing to the high prevalence of iron deficiency after surgery, it is unfortunate that the evidence behind the clinical practice guidelines (CPGs) for treatment of iron deficiency in the form of non-heme iron supplementation is poor. Without effective treatment of iron deficiency, devastating consequences may occur, such as fatigue, weakness, headaches, anemia, and a decline in cognitive performance, all of which negatively affect quality of life (QOL). Our first investigation was an observational, cross-sectional study conducted to explore the impact of dietary and supplemental sources of iron and absorptive factors on iron status after Roux-en-Y gastric bypass (RYGB) bariatric surgery. Patients were females aged 18 to 50 years, who had undergone RYGB at least 6 months previously. Blood draws for concentrations of serum ferritin, total iron binding capacity (TIBC), soluble transferrin receptor (sTfR), and hemoglobin, were performed to determine iron status. Three-day food and supplement logs were completed by patients and analyzed via Nutrition Data Systems for Research (NDSR). Dietary heme iron intake was calculated manually using previously published food composition tables. Comparing subjects who were found to be iron sufficient (N=21) to those who were iron deficient (N=15), no difference was seen in age, years since surgery, or BMI. Only 36% of the total population was adhering to the prophylactic oral iron supplement guidelines of at least 45 mg/day. We used multiple linear regression to show associations between biomarkers of iron status and nutrient intake in RYGB patients. We found that dietary heme iron, dietary vitamin C, and taking an iron supplement of at least 45 mg/day are the factors most associated with improved iron status after RYGB. Our findings suggest that diet is extremely important after surgery, despite known malabsorption. If patients were nutritionally educated to increase dietary heme iron by 0.5 mg/d, increase dietary vitamin C by 20 mg/d, and take an iron supplement of at least 45 mg/d (which are all realistic to achieve), it is predicted that ferritin will improve above 20 μg/L, which is the cut-off for diagnosis of iron deficiency. Our second investigation used a randomized, controlled, single-blind study design to compare the efficacy of oral iron supplementation using non-heme versus heme iron for repletion of iron deficiency in patients who have had RYGB. Patients were screened to determine iron status, and if iron deficient, they were randomized to receive non-heme iron (ferrous sulfate) or heme iron (HIP) supplementation for 8 weeks. Iron status, iron supplement adherence/tolerance, and fatigue/QOL were assessed at baseline, and 2, 4, and 8 week follow-up. Fourteen subjects enrolled in the 8-week study: their age was 41.5 years ± 6.8 (standard deviation), BMI was 34.4 kg/m2 ± 5.9, and time since surgery was 6.9 years ± 3.1. Demographic and iron status characteristics were similar between ferrous sulfate and HIP treatment groups. Patients receiving ferrous sulfate (dosage as outlined in the CPGs) showed significant improvement in ferritin, sTfR, TIBC, and hemoglobin after 8 weeks of supplementation; however, fatigue/QOL factors did not improve. Patients receiving HIP did not show improvements in any of the iron status measures, but factors of QOL (energy/fatigue and general health) improved. Adverse GI symptoms were reported in both groups, but this change was not significant after 8 weeks of supplementation. Compliance was strictly controlled via pill count in both ferrous sulfate and HIP groups, at 95% and 94%, respectively. Collectively, our observations suggest that diet and oral iron supplementation are extremely important in order for patients to achieve or maintain adequate iron status after surgery. Even with known malabsorption after surgery, favorable iron status can be predicted if patients increase dietary heme iron and vitamin C intake, along with taking an oral iron supplement of at least 45 mg/day. In addition, the oral iron supplementation recommendations to treat iron deficiency (ID) after surgery, as outlined in the CPGs, are efficacious. However, compliance to the regimen and adverse GI-related symptoms may limit effectiveness in a free-living environment.

Degree

M.S.

Advisors

Gletsu-Miller, Purdue University.

Subject Area

Nutrition

COinS