Carrot leaves maintain liver vitamin A concentrations in mongolian gerbils regardless of the alpha- to beta-carotene ratio when beta-carotene equivalents are equalized

Authors: TITCOMB, TYLER - University Of Wisconsin; KAEPPLER, MIKAYLA - University Of Wisconsin; SHANNON, JAMIE - University Of Wisconsin; Simon, Philipp; TANUMIHARDJO, SHERRY - University Of Wisconsin

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2019
Publication Date: 5/3/2019
Citation: Titcomb, T.J., Kaeppler, M.S., Sandoval Cates, S.B., Shannon, J.M., Simon, P.W., Tanumihardjo, S.A. 2019. Carrot leaves maintain liver vitamin A concentrations in male mongolian gerbils regardless of the ratio of alpha- to beta-carotene when beta-carotene equivalents are equalized. Journal of Nutrition. 149(6):951-958. https://doi.org/10.1093/jn/nxz036.
DOI: https://doi.org/10.1093/jn/nxz036

Interpretive Summary: Carrot is an unusual source of dietary vitamin A because orange carrots contain two different chemicals that form vitamin A: alpha- carotene and beta-carotene. There are very few other plants that provide dietary vitamin A from alpha- carotene, so the efficacy of alpha- carotene in meeting vitamin A requirements is not known. To address this question, this study used diets varying in the alpha- to beta-carotene ratio fed to gerbils to determine if both chemicals were efficacious in maintaining a healthy vitamin A status. Regardless of the alpha- to beta-carotene ratio, a healthy vitamin A status was observed. This study is of interest to nutritionists, medical researchers, and physicians involved in both research and in clinical medicine.

Technical Abstract: Background: Carrots are an important horticultural crop that contain provitamin A carotenoids (PAC). Orange carrots have high levels of alpha-carotene, which upon central cleavage yields one retinal and one alpha-retinal molecule. The leaves of carrot plants have different carotenoid profiles than the roots but are a source of PAC when consumed as an herb or vegetable. Objective: Mongolian gerbils 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 affected bioefficacy. Methods: After 3-wk washout, baseline gerbils were killed (n = 6), and remaining gerbils (n = 60) were split into 6 groups to receive either four carrot leaf-fortified (1.03-1.23%) feeds equalized for beta-carotene equivalents (beta-CE) with differing ratios of alpha- to beta-carotene, or VA-deficient feed with (VA+) or without (VA-) a retinyl acetate supplement. After 4 wks, gerbils were killed. Serum and livers were collected and analyzed for retinoids by HPLC. Results: The VA+ group had higher total liver VA micrograms than all other groups. The carrot leaf-treatment groups had similar liver VA micrograms and did not differ from baseline micrograms; however, VA- did not differ from leaf-fed groups. Alpha-Retinol accumulated in livers and was correlated to total alpha-carotene consumption. Overall bioefficacy factors ranged from 4.2 to 6.2 micrograms betaCE to 1 microgram retinol. Serum retinol concentrations did not differ among groups. Conclusions: Carrot leaves maintained VA status in gerbils regardless of the alpha- to beta-carotene ratio. The bioconversion of PAC to retinol from carrot leaves in gerbils was similar to that of other green leafy vegetables, making the addition of carrot leaves to human food and animal feeds a viable method to improve dietary PAC content.