The association of dietary flavonoids, magnesium and their interaction effect with metabolic syndrome in Chinese adults: a prospective cohort study.

To systematically analyze the association of the specific flavonoids, magnesium and their interactions from different food sources with metabolic syndrome (MetS) and its components in cohort study. A total of 6417 participants aged from 20 to 74 years from the Harbin Cohort Study on Diet, Nutrition and Chronic Non-communicable Diseases (HDNNCDS) were included. Multivariate logistic regression analyses, forest plot and Cubic splines were performed in the study. After a 5.3-year follow-up, 1283 incident cases of MetS were reported. Those with a higher total flavonoids intake had a lower risk of MetS (fourth vs. first quartile, relative risk (RR): 0.58; 95% CI: 0.37, 0.93; P = 0.024) and central obesity (0.56; 0.33, 0.95; P = 0.032). Further analysis showed that the specific flavonoids quercetin, kaempferol, isorhamnetin, luteolin, and flavonoids from fruits, potatoes and legumes had the similar associations with the risk of MetS and central obesity (P < 0.05 for all). A higher intake of total flavonoids, quercetin and luteolin combined with high level of magnesium was more strongly associated with a lower risk of MetS (0.60; 0.45, 0.81 for total; 0.61; 0.45, 0.82 for quercetin; 0.52; 0.38, 0.71for luteolin; all P for interaction < 0.01). Dose response effects showed an L-shaped curve between the total intake of five flavonoids and the risk of MetS. A higher flavonoids intake is associated with a lower risk of MetS and central obesity, their combination with magnesium helps to strengthen their negative association with MetS.