Beta-carotene is an important vitamin A source for humans

Abstract

Experts in the field of carotenoids met at the Hohenheim consensus conference in July 2009 to elucidate the current status of β-carotene research and to summarize the current knowledge with respect to the chemical properties, physiological function, and intake of β-carotene. The experts discussed 17 questions and reached an agreement formulated in a consensus answer in each case. These consensus answers are based on published valid data, which were carefully reviewed by the individual experts and are justified here by background statements. Ascertaining the impact of β-carotene on the total dietary intake of vitamin A is complicated, because the efficiency of conversion of β-carotene to retinol is not a single ratio and different conversion factors have been used in various surveys and following governmental recommendations within different countries. However, a role of β-carotene in fulfilling the recommended intake for vitamin A is apparent from a variety of studies. Thus, besides elucidating the various functions, distribution, and uptake of β-carotene, the consensus conference placed special emphasis on the provitamin A function of β-carotene and the role of β-carotene in the realization of the required/recommended total vitamin A intake in both developed and developing countries. There was consensus that β-carotene is a safe source of vitamin A and that the provitamin A function of β-carotene contributes to vitamin A intake.

FIGURE 1

Contribution of preformed vitamin A and β-carotene to the total vitamin A intake. (A) Relation between the required vitamin A intake (Ref = reference value for the given population) and the intake of preformed vitamin A products from food. If this intake is not sufficient, the difference (gap) between the reference intake and the real intake of preformed vitamin A has to be filled by β-carotene. Some theoretical intake situations are shown in (B). Intakes of preformed vitamin A and β-carotene after conversion to RE. Under intake situations 1 and 2 (group I), the reference value is reached largely independently of the conversion factor for β-carotene. Under intake situations 3 and 4 (group II), the reference value is reached if the conversion factor used is adequate. Group III (intake situations 5, 6, and 7) do not reach the reference value. Please note that reference values and conversion factors currently used are different in different countries.

FIGURE 2

Reduced conversion efficiency of β-carotene to vitamin A via BCMO1 depending on genetic variations. (1) see reference (138). (2) see reference (139).

FIGURE 3

Preformed retinol and provitamin A intakes in different female age groups within the UK [based on data from (150)]. Proportions of women of different ages in the UK with retinol (A,B) and provitamin A (C,D) intakes from food sources and supplements (A,C) or from food sources alone (B,D) below the RNI or LRNI. The RNI for retinol is 600 μg/d and for LRNI it is 250 μg/d. Provitamin A intake is the sum of β-carotene and one-half the amount of α-carotene and β-cryoptoxanthin consumed. Data are from (150).