The purpose of this study was to determine the effect of pectin on plasma response to beta-carotene in humans. Using a crossover design, we evaluated the effect on plasma beta-carotene in seven subjects when 12 g citrus pectin was added to a 2092 kJ (500 kcal) controlled meal with 25 mg beta-carotene. Plasma samples were collected at 0, 8, 30, 48, and 192 h after the meals. Plasma beta-carotene was quantified with the use of HPLC. The increase in plasma beta-carotene concentration was significantly reduced by pectin at 30 and 192 h (paired t test; P less than 0.005 and less than 0.05, respectively). Mean percent increase in plasma beta-carotene concentration at 30 h after the meal with beta-carotene was reduced by more than one-half when pectin was added to the meal. These results indicate that the inhibitory effect of pectin may provide one explanation for observations of reduced plasma beta-carotene response in humans after the ingestion of carotenoid-rich foods when compared with equivalent doses of beta-carotene supplements.