Polyphenols are abundant micronutrients in our diet, and evidence for their role in
the prevention of degenerative diseases is emerging. Bioavailability differs greatly
from one polyphenol to another, so that the most abundant polyphenols in our diet
are not necessarily those leading to the highest concentrations of active metabolites
in target tissues. Mean values for the maximal plasma concentration, the time to reach
the maximal plasma concentration, the area under the plasma concentration-time curve,
the elimination half-life, and the relative urinary excretion were calculated for
18 major polyphenols. We used data from 97 studies that investigated the kinetics
and extent of polyphenol absorption among adults, after ingestion of a single dose
of polyphenol provided as pure compound, plant extract, or whole food/beverage. The
metabolites present in blood, resulting from digestive and hepatic activity, usually
differ from the native compounds. The nature of the known metabolites is described
when data are available. The plasma concentrations of total metabolites ranged from
0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary
excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol.
Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins,
flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed
polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins.
Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols.
These data may be useful for the design and interpretation of intervention studies
investigating the health effects of polyphenols.