Dietary flavonoids: bioavailability, metabolic effects, and safety

Annu Rev Nutr. 2002;22:19-34. doi: 10.1146/annurev.nutr.22.111401.144957. Epub 2002 Jan 4.


Flavonoids comprise the most common group of plant polyphenols and provide much of the flavor and color to fruits and vegetables. More than 5000 different flavonoids have been described. The six major subclasses of flavonoids include the flavones (e.g., apigenin, luteolin), flavonols (e.g., quercetin, myricetin), flavanones (e.g., naringenin, hesperidin), catechins or flavanols (e.g., epicatechin, gallocatechin), anthocyanidins (e.g., cyanidin, pelargonidin), and isoflavones (e.g., genistein, daidzein). Most of the flavonoids present in plants are attached to sugars (glycosides), although occasionally they are found as aglycones. Interest in the possible health benefits of flavonoids has increased owing to their potent antioxidant and free-radical scavenging activities observed in vitro. There is growing evidence from human feeding studies that the absorption and bioavailability of specific flavonoids is much higher than originally believed. However, epidemiologic studies exploring the role of flavonoids in human health have been inconclusive. Some studies support a protective effect of flavonoid consumption in cardiovascular disease and cancer, other studies demonstrate no effect, and a few studies suggest potential harm. Because there are many biological activities attributed to the flavonoids, some of which could be beneficial or detrimental depending on specific circumstances, further studies in both the laboratory and with populations are warranted.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacokinetics*
  • Antineoplastic Agents, Phytogenic / pharmacology
  • Antioxidants / pharmacokinetics*
  • Antioxidants / pharmacology
  • Biological Availability
  • Cardiovascular Diseases / epidemiology
  • Cardiovascular Diseases / prevention & control
  • Diet*
  • Epidemiologic Studies
  • Estrogen Receptor Modulators / pharmacokinetics*
  • Estrogen Receptor Modulators / pharmacology
  • Flavanones*
  • Flavonoids / pharmacokinetics*
  • Flavonoids / pharmacology
  • Flavonols
  • Humans
  • Intestinal Absorption
  • Isoflavones
  • Neoplasms / epidemiology
  • Neoplasms / prevention & control
  • Phenols
  • Polymers
  • Safety


  • Antineoplastic Agents, Phytogenic
  • Antioxidants
  • Estrogen Receptor Modulators
  • Flavanones
  • Flavonoids
  • Flavonols
  • Isoflavones
  • Phenols
  • Polymers
  • flavanone