Yellow maize with high b-carotene is an effective source of vitamin A

Background: The bioconversion efficiency of yellow maize b-carotene to retinol in humans is unknown. Objective: The objective of this study was to determine the vitamin A value of yellow maize b-carotene in humans. Design: High b-carotene–containing yellow maize was grown in a hydroponic medium with 23 atom% 2H2O during grain development. Yellow maize b-carotene showed the highest abundance of enrichment as [2H9]b-carotene. Eight healthy Zimbabwean men volunteered for the study. On day 1 after a fasting blood draw, subjects consumed 300 g yellow maize porridge containing 1.2 mg b-carotene, 20 g butter, and a 0.5-g corn oil capsule. On day 8, fasting blood was drawn, and subjects consumed 1 mg [13C10]retinyl acetate in a 0.5-g corn oil capsule and 300 g white maize porridge with 20 g butter. Thirty-six blood samples were collected from each subject over 36 d. Concentrations and enrichments of retinol and b-carotene in labeled doses and serum were determined with the use of HPLC, gas chromatography–mass spectrometry, and liquid chromatography– mass spectrometry. Results: The area under the curve (AUC) of retinol from 1.2 mg yellow maize b-carotene was 72.9 nmol d, and the AUC of retinol from 1 mg retinyl acetate 13C10 was 161.1 nmol d. The conversion factor of yellow maize b-carotene to retinol by weight was 3.2 6 1.5 to 1. Conclusion: In 8 healthy Zimbabwean men, 300 g cooked yellow maize containing 1.2 mg b-carotene that was consumed with 20.5 g fat showed the same vitamin A activity as 0.38 mg retinol and provided 40–50% of the adult vitamin A Recommended Dietary Allowance. This trial was registered at clinicaltrials.gov as NCT00636038. Am J Clin Nutr 2011;94:510–9