Higher toenail selenium is associated with increased insulin resistance risk in omnivores, but not in vegetarians

Abstract Background The relationship between selenium (Se) and insulin resistance remains unclear. We aim to evaluate the association between toenail Se levels and insulin resistance in China.Methods In this cross-sectional study, 220 vegetarians and 220 age-sex- matched omnivores from Shanghai were included. The toenail Se levels were measured by inductively coupled plasma mass spectrometry method. Dietary Se intakes were assessed by the 24-hour dietary recall questionnaire. Blood samples were collected to examine fasting blood glucose and fasting insulin concentrations. Insulin resistance index (HOMA-IR) and insulin secretion index (HOMA-B) were calculated to assess insulin resistance. The multilinear regression models were performed, and the following covariates were included in the models: age, sex, BMI, alcohol consumption, income, and daily dietary intakes (energy, protein, fat, carbohydrate, and fiber).Results Toenail Se levels were not associated with insulin resistance among vegetarians but were positively associated with fasting insulin levels (β=1.030, 95% CI: 0.393, 1.667) and HOMA-IR (β=0.245, 95% CI: 0.098, 0.392) in omnivores. Stratifying the results by Se intake levels in the omnivores revealed a significant association among those with dietary Se intake ≥ 60 μg/d; insulin level (β=1.053, 95% CI: 0.415, 1.691) and HOMA-IR (β=13.271, 95% CI: 4.433, 22.109) but not in those with < 60 μg/d ; insulin level (β=2.146, 95% CI: -0.710, 5.002) and HOMA-IR (β=13.766, 95% CI: -46.868, 74.400).Conclusions Higher toenail Se levels were associated with increased insulin resistance risk in Chinese omnivores, but not in vegetarians.