Iodine Status After Bariatric Surgery-a Prospective 10-Year Report from the Swedish Obese Subjects (SOS) Study

Context Bariatric surgery can lead to nutrient deficiencies. Gastric by-pass (GBP) entails restriction and malabsorption, whereas, vertical banded gastroplasty (VBG) is only restrictive. Objective The objective of this study is to study whether GBP-patients develop iodine deficiency from malabsorption, and if GBP-and VBG-patients develop lower 24-h urinary iodine excretion (24-UIE) than obese non-operated controls (OB-controls) due to lower iodine intake. Design The Swedish Obese Subjects (SOS) study is a prospective, non-randomized study of 4047 obese patients included 1987-2001, who chose bariatric surgery or nonsurgical treatment. SOS-groups were compared at baseline, after 2 and 10 years and with population-based subsamples (MONICA-controls). Patients One hundred eighty-eight GBP-patients were matched with 188 VBG-patients and 188 OB-controls and with three subgroups from 412 MONICA-controls. Main Outcome Measurements Primary outcome was 24-UIE. Secondary outcomes were iodine intake, iodine supplementation, TSH, FT4, and thyroid morbidity. Results At baseline, median 24-UIE was higher in GBP-patients, VBG-patients and OB-controls than in MONICA-controls (214, 201, 203 and 137 mu g/day, p < 0.001). At 10 years, 24-UIE in GBP-patients (161 mu g/day) and VBG-patients (149 mu g/day) was lower compared with baseline (p < 0.01) and OB-controls (189 mu g/day, p < 0.01), but similar to 24-UIE in MONICA-controls (137 mu g/day). The 10-year-dietary iodine intake was similar in GPB-patients and OB-controls, but higher in VBG-patients. Iodine supplementation was taken by 0-9% in SOS-groups. Conclusion After surgery, GBP-and VBG-patients did not suffer from iodine deficiency, but both groups had lower iodine status than OB-controls. Dietary supplements recommended after bariatric surgery do not need to include iodine, in iodine sufficient countries.