Postprandial Duration Influences the Association of Insulin-Related Dietary Indexes and Plasma C-peptide Concentrations in Adult Men and Women

Abstract

The dietary insulin index (II) directly quantifies dietary effects on postprandial insulin secretion, whereas the empirical dietary index for hyperinsulinemia (EDIH), based on fasting C-peptide concentrations, is primarily reflective of insulin resistance. How these scores are related to nonfasting C-peptide in cohort studies has not been examined. We investigated the extent to which EDIH and II scores predict plasma C-peptide concentrations, in cross-sectional analyses by postprandial duration at blood collection from 1 to ≥15 h. Both EDIH and II scores were calculated from food-frequency questionnaire data reported by 3964 men in the Health Professionals Follow-up Study (1993-1995) and 6215 women in the Nurses' Health Study (1989-1990) who were not diabetic. We constructed 12 multivariable-adjusted linear regression models separately in men and women, by postprandial duration, to calculate relative differences and absolute values of plasma C-peptide concentrations in dietary index quintiles. In both men and women, C-peptide concentrations were elevated 1-2 h after eating and declined with increasing postprandial duration. In men, percent differences in C-peptide concentration in the highest compared with lowest dietary index quintile were: EDIH: 0-1 h: 50%; 2 h: 22%; 14 h: 14%; ≥15 h: 30% (all P-trend<0.05). II: 0-1 h: 19% (P-trend=0.09); 2 h: 3% (P-trend=0.09); 14 h: -6% (P-trend=0.17); ≥15 h: -15% (P-trend=0.02). Corresponding results among women were: EDIH: 0-1 h: 29% (P-trend=0.002); 2 h: 33% (P-trend=0.009); 14 h: 44% (P-trend<0.0001); ≥15h: 40% (P-trend<0.0001). II: 0-1 h: -12% (P-trend=0.09); 2 h: 17% (P-trend=0.09); 14 h: -14% (P-trend=0.009); ≥15 h: -3% (P-trend=0.37). The EDIH was superior to the II in predicting both fasting and nonfasting C-peptide concentrations, suggesting that the EDIH may be better in assessing dietary effects of hyperinsulinemia on disease risk in adult men and women.