Dietary patterns and C-peptide concentrations in a Japanese working population

Objective: It remains unsettled whether dietary patterns play a role in insulin resistance. We assessed the association of major dietary patterns with C-peptide concentrations in a Japanese working population. Methods: A cross-sectional study was conducted in 456 municipal employees (270 men and 186 women) 21 to 67 y old who participated in a health survey at the time of their periodic checkup. The dietary patterns were derived by using the principal component analysis of the consumption of 52 food and beverage items, which was assessed by a validated brief dietary history questionnaire. Multiple regression analysis was used to estimate the means of C-peptide concentrations across tertiles of each dietary pattern score with the adjustment of potential confounders, including age, body mass index, physical activity, smoking, alcohol drinking, and energy intake. Results: We identified three dietary patterns: healthy, animal food, and Westernized breakfast patterns. The Westernized breakfast pattern was characterized by high intakes of bread, confectionaries, and milk and yogurt but low intakes of rice and alcohol and was inversely associated with C-peptide concentrations in women but not in men. The multivariable-adjusted means of C-peptide concentrations were 1.03 ng/mL (95% confidence interval 0.95-1.12), 0.95 ng/mL (95% confidence interval 0.88-1.03), and 0.89 ng/mL (95% confidence interval 0.82-0.97) for the lowest through the highest tertiles of the Westernized breakfast pattern score (P for trend = 0.015) in women. Other dietary patterns were not appreciably associated with C-peptide concentrations. In a subgroup, similar associations were observed between dietary patterns and the homeostasis model assessment of insulin resistance. Conclusion: The Westernized breakfast pattern may be associated with a lower insulin resistance in Japanese women.