Dear Editor,

I read the article “Vitamin D Supplementation Efficacy: Sleeve Gastrectomy Versus Gastric Bypass Surgery” [1]. I was concerned about the aim of the study trying to show any differences after two bariatric operations in a small group of patients (11 versus 12 patients). Three months after the bariatric procedures and after the intense supplementation with vitamin D, 26.1 % of patients had vitamin D deficiency in both groups. I think that this study is based in a very small population, without any power analysis data given. The authors do not also reveal the possible problems with unmasking subclinical parathyroid glands adenomas with intensive vitamin D supplementation [2]. The rate of these problems and the rate of preoperative secondary hyperparathyroidism could not possibly be revealed with such a small group of patients [3]. I think a study with more patients will enlighten us about the possible role of vitamin D supplementation after these two bariatric procedures. Assessment of vitamin D deficiency should also be performed after a longer period after the operation.