Associations of dietary flavonoids with risk of type 2 diabetes, and markers of insulin resistance and systemic inflammation in women: a prospective study and cross-sectional analysis.
OBJECTIVE
Flavonoids, as antioxidants, may prevent the progressive impairment of pancreatic beta-cell function due to oxidative stress and may thus reduce the occurrence of type 2 diabetes. The aim of the present study was to examine the association of dietary flavonol and flavone intake with type 2 diabetes, and biomarkers of insulin resistance and systemic inflammation.


METHODS
In 38,018 women aged > or =45 y and free of cardiovascular disease, cancer and diabetes with an average 8.8 y of follow-up, we calculated relative risks (RRs) of incident type 2 diabetes (1,614 events) according to dietary intake of total or individual flavonols and flavones and flavonoid-rich foods. We also measured and examined plasma concentrations of insulin, HbA(1C), CRP, and IL-6 in relation to total flavonol and flavone intake among 344 nondiabetic women.


RESULTS
During 332,905 person-years of follow-up, none of total flavonols and flavones, quercetin, kaempferol, myricetin, apigenin, and luteolin was significantly associated with risk of type 2 diabetes. Among flavonoid-rich foods, apple and tea consumption was associated with diabetes risk. Women consuming > or =1 apple/d showed a significant 28% reduced risk of type 2 diabetes compared with those who consumed no apples (the multivariate-adjusted RR = 0.72, 95% CI: 0.56, 0.92; p = 0.006 for trend). Tea consumption was also inversely associated with diabetes risk but with a borderline significant trend (> or =4 cups/d vs. none: RR 0.73, 95% CI: 0.52-1.01; p for trend = 0.06). In 344 nondiabetic women, total intake of flavonols and flavones was not significantly related to plasma concentrations of fasting insulin, HbA(1C), CRP, or IL-6.


CONCLUSIONS
These results do not support the hypothesis that high intake of flavonols and flavones reduces the development of type 2 diabetes, although we cannot rule out a modest inverse association with intake of apples and tea.
Song
Yiqing
Y
Division of Preventive Medicine, Brigham and Women's Hospital, Boston, MA 02215, USA. ysong@hsph.harvard.edu
Manson
JoAnn E
JE
Buring
Julie E
JE
Sesso
Howard D
HD
Liu
Simin
S
D015415:Biomarkers / Q000032:analysis; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology* / Q000209:etiology / Q000378:metabolism; D004032:Diet; D005260:Female; D005419:Flavonoids / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D005500:Follow-Up Studies; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D007333:Insulin Resistance; D027845:Malus; D008875:Middle Aged; D018384:Oxidative Stress / Q000187:drug effects; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors; D013662:Tea
D015415:Biomarkers; D005419:Flavonoids; D013662:Tea