[Study on the mediating and moderating effects of food intake on blood glucose levels]

Objective: Analyze the mediating and moderating effects of the relationship between food intake and blood glucose levels. Methods: This study uses data from the China Health and Nutrition Survey project in the survey 2018, involving 11 043 adults aged 18 years or older, who have complete dietary data, waist circumference (WC), glycated hemoglobin A1c (HbA1c) indicators, and other key variables. Food consumption data was gathered via three consecutive 24-hour dietary recalls and weighing accounting method, which included two weekdays and one weekend day. The average daily intake of various foods and total energy intake were calculated. The mediation effect and moderation effect analysis were conducted using simple mediation models, direct moderation effect models, and moderated mediation analysis theoretical models. The confidence interval method (bootstrap method) was performed for testing and analysis. Results: A total of 4 951 males and 6 092 females were included in the stratified analysis by gender. The mediating effects on the rice, wheat, and red meat→WC→HbA1c were all statistically significant in males. The standardized coefficients were -0.009 (P<0.001), 0.013 (P<0.001), and -0.005 (P=0.008), respectively. In females, the mediating effect on the wheat→WC→HbA1c was statistically significant, and the standardized coefficient was 0.017 (P<0.001); the impact of red meat intake on HbA1c is negatively regulated by the intake of dark vegetables, with a direct moderating effect; the standardized coefficient of the interaction term between red meat and dark vegetables was -0.024 (P=0.008). Dark vegetables have a moderated mediator on the pathway from rice to WC and HbA1c (a₃b₁=-0.003, P=0.041) in males. The mediating effect of WC is negatively regulated by the intake of dark vegetables (mediation effect difference U_1/-1=-0.006, P=0.048). Dark vegetables showed a moderated mediator on the pathway from wheat to WC and HbA1c (a₃b₁=-0.004, P=0.045) in females. The mediating effect of WC is negatively regulated by the intake of dark vegetables (mediation effect difference U_1/-1=-0.009, P=0.049). Conclusions: Changes in WC indicators caused by rice, wheat, and red meat intake. WC could mediate between rice, wheat, red meat, and HbA1c. Dark vegetables directly or indirectly regulate HbA1c levels by interacting with rice, wheat, and red meat.