title: Spinach or carrots can supply significant amounts of vitamin A as assessed by feeding with intrinsically deuterated vegetables.
abstract: BACKGROUND
  The vitamin A value of spinach and carrots needs to be measured directly.
  
  
  OBJECTIVE
  The objective was to determine the vitamin A value of intrinsically labeled dietary spinach and carrots in humans.
  
  
  METHODS
  Spinach and carrots were intrinsically labeled by growing these plants in 25 atom% 2H2O nutrient solution. Growth in this medium yielded a range of trans beta-carotene (tbeta-carotene) isotopomers with a peak enrichment at molecular mass plus 10 mass units. Seven men with a mean (+/-SD) age of 59.0 +/- 6.3 y and a body mass index (in kg/m2) of 25.7 +/- 1.5 consumed puréed spinach (300 g, 20.8 micromol tbeta-carotene equivalents) or carrots (100 g, 19.2 micromol tbeta-carotene equivalents) with a standardized liquid diet (no extra fiber) in random order 4 mo apart. Seven women with a mean (+/-SD) age of 55.5 +/- 6.3 y and a body mass index of 26.4 +/- 4.2 consumed puréed spinach only (300 g, 20.0 micromol tbeta-carotene equivalents). A reference dose of [13C8]retinyl acetate (8.9 micromol) in oil was given to each subject 1 wk after each vegetable dose. Blood samples were collected over 35 d.
  
  
  RESULTS
  Areas under the curve for total labeled serum beta-carotene responses were 42.4 +/- 8.5 nmol.d per micromol spinach beta-carotene and 119.8 +/- 23.0 nmol.d per micromol carrot beta-carotene (P < 0.01). Compared with the [13C8]retinyl acetate reference dose, spinach tbeta-carotene conversion to retinol was 20.9 +/- 9.0 to 1 (range: 10.0-46.5 to 1) and carrot tbeta-carotene conversion to retinol was 14.8 +/- 6.5 to 1 (range: 7.7-24.5 to 1) by weight.
  
  
  CONCLUSIONS
  Spinach and carrots can provide a significant amount of vitamin A even though the amount is not as great as previously proposed. Food matrices greatly affect the bioavailability of plant carotenoids, their efficiency of conversion to vitamin A, or both.
authors.affiliation: Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA, 02111, USA. guangwen.tang@tufts.edu
authors.forename: Guangwen
authors.initials: G
authors.lastname: Tang
authors.forename: Jian
authors.initials: J
authors.lastname: Qin
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Dolnikowski
authors.forename: Robert M
authors.initials: RM
authors.lastname: Russell
authors.forename: Michael A
authors.initials: MA
authors.lastname: Grusak
mesh_terms: D000368:Aged; D000975:Antioxidants / Q000032:analysis / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001682:Biological Availability; D002247:Carbon Isotopes; D018552:Daucus carota / Q000737:chemistry*; D003903:Deuterium; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006801:Humans; D007408:Intestinal Absorption; D007553:Isotope Labeling; D008297:Male; D008875:Middle Aged; D009753:Nutritive Value; D018724:Spinacia oleracea / Q000737:chemistry*; D014801:Vitamin A / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*; D019207:beta Carotene / Q000032:analysis / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D000975:Antioxidants; D002247:Carbon Isotopes; D019207:beta Carotene; D014801:Vitamin A; D003903:Deuterium