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Am J Clin Nutr. 2005 Oct;82(4):821-8.

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

Author information

  • 1Jean Mayer US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, MA, 02111, USA. guangwen.tang@tufts.edu

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.

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.

PMID:
16210712
[PubMed - indexed for MEDLINE]
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