Spinach or carrots can supply significant amounts of vitamin A as assessed by feeding with intrinsically deuterated vegetables

Am J Clin Nutr. 2005 Oct;82(4):821-8. doi: 10.1093/ajcn/82.4.821.


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.

Design: 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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aged
  • Antioxidants / analysis
  • Antioxidants / pharmacokinetics*
  • Area Under Curve
  • Biological Availability
  • Carbon Isotopes
  • Daucus carota / chemistry*
  • Deuterium
  • Female
  • Gas Chromatography-Mass Spectrometry / methods
  • Humans
  • Intestinal Absorption
  • Isotope Labeling
  • Male
  • Middle Aged
  • Nutritive Value
  • Spinacia oleracea / chemistry*
  • Vitamin A / analysis
  • Vitamin A / blood
  • Vitamin A / pharmacokinetics*
  • beta Carotene / analysis
  • beta Carotene / blood
  • beta Carotene / pharmacokinetics*


  • Antioxidants
  • Carbon Isotopes
  • beta Carotene
  • Vitamin A
  • Deuterium