title: Yellow maize with high β-carotene is an effective source of vitamin A in healthy Zimbabwean men.
abstract: BACKGROUND
  The bioconversion efficiency of yellow maize β-carotene to retinol in humans is unknown.
  
  
  OBJECTIVE
  The objective of this study was to determine the vitamin A value of yellow maize β-carotene in humans.
  
  
  METHODS
  High β-carotene-containing yellow maize was grown in a hydroponic medium with 23 atom% (2)H(2)O during grain development. Yellow maize β-carotene showed the highest abundance of enrichment as [(2)H(9)]β-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 β-carotene, 20 g butter, and a 0.5-g corn oil capsule. On day 8, fasting blood was drawn, and subjects consumed 1 mg [(13)C(10)]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 β-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 β-carotene was 72.9 nmol · d, and the AUC of retinol from 1 mg retinyl acetate (13)C(10) was 161.1 nmol · d. The conversion factor of yellow maize β-carotene to retinol by weight was 3.2 ± 1.5 to 1.
  
  
  CONCLUSIONS
  In 8 healthy Zimbabwean men, 300 g cooked yellow maize containing 1.2 mg β-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.
authors.affiliation: Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA.
authors.forename: Tawanda
authors.initials: T
authors.lastname: Muzhingi
authors.forename: Tendekayi H
authors.initials: TH
authors.lastname: Gadaga
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Siwela
authors.forename: Michael A
authors.initials: MA
authors.lastname: Grusak
authors.forename: Robert M
authors.initials: RM
authors.lastname: Russell
authors.forename: Guangwen
authors.initials: G
authors.lastname: Tang
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D008297:Male; D008875:Middle Aged; D014801:Vitamin A / Q000378:metabolism*; D003313:Zea mays / Q000737:chemistry*; D015030:Zimbabwe; D019207:beta Carotene / Q000032:analysis / Q000378:metabolism*
chemical_list: D019207:beta Carotene; D014801:Vitamin A