Intestinal Malabsorption Syndrome and Bariatric Surgery and Vitamin D

Vitamin D deficiency is common in patients with malabsorption syndromes and in patients submitted to bariatric procedures. Since 80% to 90% of vitamin D is synthetized in the skin, it is not clear how intestinal malabsorption causes vitamin deficiency. However, when vitamin D deficiency correction or supplementation is needed, the malabsorption component gains importance. Different vitamin D supplementation doses are suggested for different entities. Despite the absence of consensus, there is the general recommendation that double or triple 25(OH) vitamin D supplementation dose is often needed. In addition, obese patients seem to have resistance to vitamin D supplementation and frequently higher doses are necessary. After bariatric surgery, vitamin D supplementation is recommended in all patients, but the supplementation doses suggested varies between 2000 U to 4000 U and dose tailored to the patient 25OH vitamin D levels is sometimes required. When vitamin D deficiency is present, some societies suggested double or triple the recommended vitamin D correction doses for the general population. Both vitamin D2 (cholecalciferol) and D3 (ergocalciferol) can be used although vitamin D2 seems to be more efficient. Calcidiol (25-hydroxycholecalciferol) is a more hydrophilic alternative and may be more easily absorbed than cholecalciferol and may be attempted when cholecalciferol fails to normalize serum 25(OH)vitamin D levels. Parenteral forms may be used if enteral formulations fail.