Insulin-related dietary indices predict 24-hour Urinary C-peptide in Adult Men

Dietary insulin index directly estimates the postprandial insulin secretion potential of foods, whereas empirical dietary index for hyperinsulinemia (EDIH) assesses insulinemic potential of usual diets based on fasting plasma C-peptide, and is primarily reflective of insulin resistance. It is unknown whether these insulin-related indices are predictive of an integrated measure of insulin secretion. We conducted a cross-sectional analysis that included 293 non-diabetic men with 24-hour urinary C-peptide data from the Men's Lifestyle Validation Study. EDIH, dietary insulin index, and dietary insulin load were calculated using validated food frequency questionnaires. We conducted multivariable-adjusted linear regression to estimate relative and absolute concentrations of 24-hour urinary C-peptide. In multivariable-adjusted models, we found a significant positive association between all three insulin-related dietary indices and 24-hour urinary C-peptide (P<0.05). Relative concentrations of 24-hour urinary C-peptide per 1-standard deviation increase in insulin-related dietary indices were: 1.12 (95% confidence interval (CI), 1.02, 1.23) for EDIH, 1.18 (95% CI, 1.07, 1.29) for dietary insulin index and 1.16 (95% CI, 1.06, 1.27) for dietary insulin load. When we further adjusted for body mass index (BMI), the association was attenuated for EDIH, to 1.07 (95% CI, 0.98, 1.16), and remained unchanged for dietary insulin index and dietary insulin load. In conclusion, EDIH, dietary insulin index, and dietary insulin load were predictive of integrated insulin secretion assessed by 24-hour urinary C-peptide. Findings after adjustment for BMI appear to confirm the relation of EDIH to insulin resistance and dietary insulin index/load to insulin secretion; the respective constructs of the two dietary indices.