Long-Term Iron and Vitamin B12 Deficiency Are Present after Bariatric Surgery, Despite the Widespread Use of Supplements

Int J Environ Res Public Health. 2021 Apr 25;18(9):4541. doi: 10.3390/ijerph18094541.


There are few long-term nutritional studies in subjects undergoing bariatric surgery that have assessed weight regain and nutritional deficiencies. In this study, we report data 8 years after surgery on weight loss, use of dietary supplements and deficit of micronutrients in a cohort of patients from five centres in central and northern Italy. The study group consisted of 52 subjects (age: 38.1 ± 10.6 y, 42 females): 16 patients had Roux-en-Y gastric bypass (RYGB), 25 patients had sleeve gastrectomy (SG) and 11 subjects had adjustable gastric banding (AGB). All three bariatric procedures led to sustained weight loss: the average percentage excess weight loss, defined as weight loss divided by excess weight based on ideal body weight, was 60.6% ± 32.3. Despite good adherence to prescribed supplements, 80.7% of subjects (72.7%, AGB; 76.7%, SG; 93.8 %, RYGB) reported at least one nutritional deficiency: iron (F 64.3% vs. M 30%), vitamin B12 (F 16.6% vs. M 10%), calcium (F 33.3% vs. M 0%) and vitamin D (F 38.1% vs. M 60%). Long-term nutritional deficiencies were greater than the general population among men for iron and among women for vitamin B12.

Keywords: Roux-en-Y gastric bypass; adjustable gastric banding; bariatric surgery; iron; nutritional deficiency; sleeve gastrectomy; vitamin B12; vitamin D.

MeSH terms

  • Adult
  • Bariatric Surgery* / adverse effects
  • Dietary Supplements
  • Female
  • Humans
  • Iron
  • Italy / epidemiology
  • Male
  • Middle Aged
  • Obesity, Morbid* / surgery
  • Retrospective Studies
  • Vitamin B 12 Deficiency* / epidemiology
  • Vitamin B 12 Deficiency* / etiology


  • Iron