title: [Vitamin A equivalence of spinach beta-carotene in human body].
abstract: OBJECTIVE
  To determine the vitamin A equivalence of spinach beta-carotene (beta-C) in human body.
  
  
  METHODS
  Spinach grown in 25 atom% 2H2O cultural solution was intrinsically labeled by deuterium. The highest enrichment of spinach trans-beta-C isotopomers was at the molecular mass of 547 (2H10 trans-beta-C). Ten healthy Chinese male adults (43-56y) were given a dose of 5.8 micromol 13C10 retinyl acetate as vitamin A reference dose. One week later, each subject was given 100g of steamed spinach (containing 7.0 micromol beta-C). Forty blood samples were collected over 56 days from each subject. A HPLC method was used to detect the concentrations of retinol and beta-C in serum, and a GC-MS method was used to detect the enrichment of the labeled retinol. Kinetic curves of the labeled retinol from the reference dose and the spinach beta-C were compared to determine the vitamin A equivalence of spinach beta-C.
  
  
  RESULTS
  The results showed that 1 nmol spinach beta-C provided (0.25 +/- 0.10) nmol retinol. The mean conversion factor of spinach beta-C to vitamin A was (9.0 +/- 4.5) : 1 by weight.
  
  
  CONCLUSIONS
  The bioconversion of spinach beta-C to vitamin A was determined in 10 Chinese male adults by stable isotope tracer and reference techniques, and the mean conversion factor was 9.0 to 1 on a weight basis.
authors.affiliation: National Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing 100050, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.forename: Zhixu
authors.initials: Z
authors.lastname: Wang
authors.forename: Yin
authors.initials: Y
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Fu
mesh_terms: D000328:Adult; D001682:Biological Availability; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D008875:Middle Aged; D018724:Spinacia oleracea / Q000737:chemistry*; D014801:Vitamin A / Q000097:blood* / Q000378:metabolism; D019207:beta Carotene / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D019207:beta Carotene; D014801:Vitamin A