Original article Serum 25-hydroxyvitamin D concentration and its association with glucose intolerance in an indigenous population Giovanna P. Abrah ~ ao a , Marcia C. Santos a, c , Jo ~ ao Paulo B. Vieira Filho a , Amaury L. Dal Fabbro b , La  ercio J. Franco b , Regina S. Moises a, * a Division of Endocrinology, Escola Paulista de Medicina, Universidade Federal de S~ ao Paulo, S~ ao Paulo, Brazil b Department of Social Medicine, Faculty of Medicine of Ribeir~ ao Preto, University of S~ ao Paulo, Ribeir~ ao Preto, Brazil c Division of Endocrinology, Faculdade de Medicina, Instituto de Ci^ encias da Saúde,Universidade Federal do Par a, Bel em, PA, Brazil article info Article history: Received 7 March 2020 Accepted 19 August 2020 Keywords: 25-Hydroxyvitamin D Vitamin D Glucose intolerance Type 2 diabetes mellitus Indigenous population summary Background and aims: Type 2 diabetes is a multifactorial disease resulting from diverse genetic and environmental factors as well as the interaction between them. Low levels of 25-hydroxyvitamin D [25(OH)D], an indicator of vitamin D status, have been associated with an increased risk of type 2 dia- betes, but not consistently. Also, it remains to be determined if this association differs among ethnic groups. Therefore, we aimed to evaluate vitamin D status and its association with glucose intolerance in a Brazilian indigenous population, the Xavante Indians. Methods: The study population consisted of 819 full Xavante Indians (410 women), aged 18 years and living in two indigenous reserves located in Mato Grosso State, central region of Brazil. Clinical exami- nation and anthropometrical measurements were made, blood samples were obtained for total cholesterol, HDL-cholesterol, triglycerides and 25(OH)D measurement. Fasting and 2-h post 75 g oral glucose load capillary glucose was measured. Vitamin D status was defined by serum 25(OH)D levels: vitamin D sufficiency (25(OH)D: 30e100 ng/mL), vitamin D insufficiency (25(OH)D: 20- <30 ng/mL) and vitamin D deficiency (25(OH)D: < 20 ng/mL). Multiple logistic regression was performed to identify independent associations between 25(OH)D levels and impaired glucose tolerance or diabetes mellitus. Results: Analyses stratified by 25(OH)D levels shows that 65.5% of the population had vitamin D defi- ciency/insufficiency (25(OH)D < 30 ng/mL). 25(OH)D concentrations were lower in individuals with impaired glucose tolerance or diabetes mellitus than in normal glucose tolerant individuals. Multiple logistic regression analysis showed an inverse association between increments of 25(OH)D and presence of diabetes mellitus (OR per 1 ng/mL increase in 25(OH)D: 0.97; 95% confidence interval: 0.95e0.99), or impaired glucose tolerance (OR per 1 ng/mL increase in 25(OH)D: 0.87; 95% confidence interval: 0.85 e0.89), in an age, sex, BMI and season of sampling-adjusted model. Conclusions: The present population-based study found a high prevalence of hypovitaminosis D among Xavante Indians. In this at-risk population of type 2 diabetes, a significant association of higher serum 25(OH)D with a decreased prevalence of diabetes mellitus and impaired glucose tolerance was observed. © 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. 1. Introduction Type 2 diabetes mellitus is a global health problem, with a rapidly growing prevalence. Currently, it is estimated that 463 million adults have diabetes worldwide and, this number is ex- pected to increase to 700 million in 2045 [1]. Despite affecting all populations, some ethnic groups have a higher susceptibility to the disease than others. In this context, Native populations in the Americas have an enormous burden of diabetes, with the Pima Indians of Arizona having the highest reported prevalence [2]. Also, we showed previously that the Xavante Indians, one of the largest native Brazilian people, have a higher prevalence of diabetes than the general Brazilian population [3]. Type 2 diabetes is a multifactorial disease resulting from diverse genetic and environmental factors, as well as the interaction be- tween them. Among the environmental factors, certain nutrients affect the disease risk. Vitamin D, a steroid hormone, has a well- established role in calcium metabolism and bone mineralization and, there is a growing body of evidence supporting a variety of * Corresponding author. Escola Paulista de Medicina, Universidade Federal de S~ ao Paulo Rua Pedro de Toledo, 781, 04039-032, S~ ao Paulo, SP, Brazil. E-mail address: rmoises@unifesp.br (R.S. Moises). Contents lists available at ScienceDirect Clinical Nutrition journal homepage: http://www.elsevier.com/locate/clnu https://doi.org/10.1016/j.clnu.2020.08.015 0261-5614/© 2020 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved. Clinical Nutrition xxx (xxxx) xxx Please cite this article as: Abrah~ ao GP et al., Serum 25-hydroxyvitamin D concentration and its association with glucose intolerance in an indigenous population, Clinical Nutrition, https://doi.org/10.1016/j.clnu.2020.08.015