• bioavailability;
  • carotene;
  • human;
  • red palm oil;
  • stable isotope;
  • vitamin A

Red palm oil (RPO) contains high concentrations of β- and α-carotene, and is presumed to possess a higher vitamin A value than other foods. The objective was to determine the metabolic vitamin A and carotene values of refined red palm oil in healthy adult subjects, using a stable isotope reference method. Twelve healthy subjects were administered a small standardised meal containing 10 g RPO (2.4 mg β-carotene and 1.8 mg α-carotene) in a blended juice-based drink also containing 2 mg tetradeuterated retinyl acetate (d4-RA) as a metabolic reference. At baseline and at several times after the test meal, the concentrations of carotenes and of d4- and d0-(unlabelled) retinyl esters, in the plasma chylomicron-rich (d < 1.006) fraction were determined by high high-performance liquid chromatography and gas chromatography mass spectrometry, respectively. The masses of palm oil-derived vitamin A and carotenes absorbed (‘yield’) were calculated assuming 80% absorption of the d4-RA reference dose. The mean yield of retinol from the RPO was 0.41 mg, ranging from 0.17 mg to 0.86 mg. The mean yields of β- and α-carotene were 0.29 mg and 0.25 mg, respectively, suggesting that β-carotene was more extensively metabolised than α-carotene. Subjects assimilated an average of 23% of the dose of carotenes, as the sum of retinol and unmetabolised carotenes. The vitamin A values of red palm oil obtained under these conditions, a mean of 0.17 mg retinol absorbed per mg β-carotene consumed (β-carotene : retinol equivalency of 5.7:1) is higher than that of all other vegetable sources we have evaluated to date.