The physiology and tissue distribution of bilberry anthocyanins were studied in mice. After oral administration of bilberry extract (100 mg/kg body weight), both unmodified and methylated anthocyanins appeared in the plasma. The plasma concentration of total anthocyanins reached a maximum of 1.18 +/- 0.3 microM after 15 min and then sharply decreased. Their urinary excretion was highest between 0 and 6 h after administration and had ceased by 24 h. The total quantities of bilberry anthocyanins excreted into urine represented 1.88% (range, 0.62% to 2.45%) of consumed anthocyanins. Thirteen anthocyanins were identified in bilberry extracts. Of these, malvidin-3-glucoside and -3-galactoside were the principal anthocyanins in the plasma 60 min after administration. When mice were maintained for 2 weeks on a diet containing 0.5% of bilberry extracts, the plasma concentration of anthocyanins reached a maximum of 0.26 muM. Anthocyanins were detected only in the liver, kidney, testes, and lung, with maximum tissue concentrations of 605, 207, 149, and 116 pmol/g, respectively. In these organs, malvidin-3-glucoside and -3-galactoside were the predominant anthocyanins. Anthocyanins were not detectable in the spleen, thymus, heart, muscle, brain, white fat, or eyes. We conclude that bilberry anthocyanins were absorbed into the body and distributed in specific organs, particularly the liver, kidney, and testis. The most common anthocyanins in tissues were malvidin glycosides.