Flavonoids, Cardiovascular Disease, and Diabetes

Abstract

Background: Flavonoids have been shown to have anti-inflammatory, antioxidant, and vasodilatory properties; mechanisms that may lead to cardio-protective benefits. Results from observational studies assessing the associations between flavonoid intake and cardiovascular disease (CVD) and type 2 diabetes mellitus have been largely equivocal. Earlier studies were limited due to lack of complete flavonoid composition databases. With the development of more complete databases, total flavonoid intake can be more accurately estimated, but the associations between them and CVD and diabetes have not been assessed in a nationally representative sample of the U.S. population. Aims: The objective of this study was to assess the relationship between dietary intake of flavonoids and risk of: 1) CVD outcomes, and 2) diabetes. Methods: Baseline data from the Third National Health and Nutrition Examination Survey (NHANES III) were collected from participants in 1988-1994 and linked with administrative records to identify CVD and diabetes outcomes. The National Death Index was used for mortality and CMS Medicare Claims and Medicare enrollment data to identify initial events. Flavonoid intake was assessed with up to four 24-hour dietary recalls and the USDA’s flavonoid databases were used to assign flavonoid values to reported food and beverage consumption. Usual intakes of flavonoids and flavonoid sub-classes were estimated using the NCI method. Hazard ratios and 95% confidence intervals were estimated using Cox proportional hazards regression modeling. Results: In this nationally representative sample of adults, from a 1988-1994 constructed cohort and followed passively for over 20 years, significant inverse associations between total flavonoids or sub-classes and CVD outcomes or diabetes were not evident. However, there was a marginal association between flavanones and CVD mortality, for males only (HR =0.93, 95 % CI 0.87, 1.00, p-value<0.04). Conclusions: In this population-based sample of individuals, associations between intakes of flavonoid and CVD mortality (with the exception of flavanone intake for men only), CVD morbidity or diabetes were not evident after 20 years of follow-up. This may be due to their low levels of usual intake, to errors in measurement of flavonoid intake, or misclassification over time of flavonoid intakes, or relatively small sample sizes.