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.

Background: Carrots are an important horticultural crop that contain provitamin A carotenoids (PACs). Orange carrots have high concentrations of alpha-carotene, which upon central cleavage yields 1 retinal and 1 alpha-retinal molecule. The leaves of carrot plants are a source of PACs when consumed. Objective: 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 alpha- to beta-carotene (alpha:beta-carotene) affected bioefficacy. Methods: 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 alpha:beta-carotene ratio) equalized to 4.8 nmol/g beta-carotene equivalents (beta CEs), or VA-deficient feed with (VA+) or without (VA-) retinyl acetate supplements. Carrot-leaf powder from 4 carrot plants with differing alpha:beta-carotene ratios was used. After 4 wk, gerbils were killed and tissues were collected and analyzed for retinoids by HPLC. Results: VA+ had higher total liver VA (means +/- SD 0.91 +/- 0.29 mu mol) 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 mu mol). VA-(0.40 +/- 0.23 mu mol VA/liver) did not differ from the leaf-fed groups, but 30% became VA deficient (defined as < 0.1 mu mol VA/g liver). alpha-Retinol accumulated in livers and lungs and was correlated to total alpha-carotene consumption (R-2 = 0.83 and 0.88, respectively; P < 0.0001). Bioefficacy factors ranged from 4.2 to 6.2 mu g beta CE to 1 mu g retinol. Conclusions: Carrot leaves maintain VA status and prevent deficiency in gerbils regardless of the alpha:beta-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.