Deficiencies in micronutrients after bariatric operations are frequent, despite routine supplementation. Main outcome measures were pre- and postoperative frequency of nutrient deficiencies and success rate of their treatment.

Between 5/2004 and 12/2006, 136 patients (m:f = 0:4) with an average body mass index of 45 (35–58) kg/m² and age of 53 (21–66) years were prospectively analysed. Laparoscopic Roux-Y-gastric bypass (LRYGB) was performed in 86 patients and laparoscopic sleeve gastrectomy (LSG) was performed in 50 patients. The patients were examined before surgery as well as 3, 6, 12, 24, 30, and 36 months postoperatively using a standard protocol including laboratory tests. The mean follow-up time was 24.4 (12–40) months; the follow-up rate was 100%.

Prior to surgery, 57% of the patients had at least one deficiency, 23% of whom had vitamin D₃ deficiency. Frequent postoperative deficiencies after LSG were zinc, vitamin D₃, folic acid, iron, and vitamin B₁₂; after LRYGB, vitamin B₁₂, vitamin D₃, zinc, and secondary hyperparathyroidism. No vitamin B₁ or B₆ deficiencies were found. Calcium levels were normal in all patients. Treatment of the deficiencies was mostly successful.

Preoperatively, 57% of morbidly obese patients already had a deficiency. Postoperatively, significantly more vitamin B₁₂ and vitamin D deficiencies and hyperparathyroidism were found in patients who had undergone LRYGB. After LSG, folate deficiency was more frequent (but not significantly so). Calcium levels were normal in all patients; therefore, parathyroid hormone and vitamin D₃ levels are more sensitive markers for early detection of disorders of calcium metabolism. Iron deficiency anaemia is most efficiently treated by IV therapy.