Dietary flavonoids: bioavailability, metabolic effects, and safety

Area of Science:

• Plant biochemistry
• Nutritional science
• Pharmacology

Background:

• Flavonoids are common plant polyphenols, contributing to the color and flavor of fruits and vegetables.
• Over 5000 types exist, categorized into six main subclasses: flavones, flavonols, flavanones, catechins, anthocyanidins, and isoflavones.
• Often found as glycosides in plants, flavonoids are known for their antioxidant and free-radical scavenging properties.

Purpose of the Study:

• To explore the potential health benefits of flavonoids.
• To review the evidence regarding flavonoid absorption, bioavailability, and epidemiological findings.
• To highlight the need for further research due to conflicting study results.

Main Methods:

• Literature review of in vitro studies on antioxidant activity.
• Analysis of human feeding studies on flavonoid absorption and bioavailability.
• Examination of epidemiological studies on flavonoid consumption and health outcomes.

Main Results:

• In vitro studies confirm potent antioxidant and free-radical scavenging activities of flavonoids.
• Human feeding studies indicate higher-than-expected absorption and bioavailability of certain flavonoids.
• Epidemiological studies present conflicting results regarding the protective effects of flavonoids against cardiovascular disease and cancer, with some showing no effect or even potential harm.

Conclusions:

• Flavonoids possess significant antioxidant properties with promising bioavailability in humans.
• The role of dietary flavonoids in human health remains uncertain due to inconsistent epidemiological evidence.
• Further laboratory and population-based studies are essential to elucidate the complex biological activities and health implications of flavonoids.