Carrot Leaves Maintain Liver Vitamin A Concentrations in Male Mongolian Gerbils Regardless of the Ratio of α- to β-Carotene When β-Carotene Equivalents Are Equalized

Abstract

Carrots are an important horticultural crop that contain provitamin A carotenoids (PACs). Orange carrots have high concentrations of α-carotene, which upon central cleavage yields 1 retinal and 1 α-retinal molecule. The leaves of carrot plants are a source of PACs when consumed. Male Mongolian gerbils aged 27-30 d were used to assess the bioefficacy of carrot leaves to maintain vitamin A (VA) status and investigate whether the ratio of α- to β-carotene (α:β-carotene) affected bioefficacy. After 3 wk depletion, baseline gerbils were killed (n=6) and the remaining gerbils (n=60) were divided into 6 groups to receive 4 VA-deficient, carrot leaf-fortified feeds (1:1.4, 1:2.5, 1:5.0, and 1:80 α:β-carotene ratio) equalized to 4.8 nmol/g β-carotene equivalents (βCEs), or VA-deficient feed with (VA+) or without (VA-) retinyl acetate supplements. Carrot-leaf powder from 4 carrot plants with differing α:β-carotene ratios was used. After 4 wk, gerbils were killed and tissues were collected and analyzed for retinoids by HPLC. VA+ had higher total liver VA (means ± SD 0.91±0.29 μmol) than all other groups (range: 0.40-0.62) (P≤0.03), and the carrot leaf treatments did not differ from baseline (0.55±0.09 μmol). VA- (0.40±0.23 μmol VA/liver) did not differ from the leaf-fed groups, but 30% became VA deficient (defined as <0.1 μmol VA/g liver). α-Retinol accumulated in livers and lungs and was correlated to total α-carotene consumption (R2=0.83 and 0.88, respectively; P<0.0001). Bioefficacy factors ranged from 4.2 to 6.2 μg βCE to 1 μg retinol. Carrot leaves maintain VA status and prevent deficiency in gerbils regardless of the α:β-carotene ratio. The bioconversion of PACs from carrot leaves to retinol is similar to what has been reported for other green leafy vegetables, making the consumption of carrot leaves a viable method to improve dietary PAC intake.