Dietary carotenoids and their role in combating vitamin A deficiency: a review of the literature.

OBJECTIVE: To evaluate the evidence that carotene-rich fruits and vegetables can overcome vitamin A deficiency.
DESIGN: Results of studies on the relationship between dietary carotenoids and vitamin A deficiency were evaluated critically.
RESULTS: Increased intake of fruits and vegetables has been shown to be related to improved vitamin A status in many cross-sectional, case-control and community-based studies, but this does not prove causality of the relationship. Many experimental studies indicating a positive effect of fruits and vegetables can be criticized for their poor experimental design while recent experimental studies have found no effect of vegetables on vitamin A status. Thus, it is too early to draw firm conclusions about the role of carotene-rich fruits and vegetables in overcoming vitamin A deficiency. Bioavailability of dietary carotenoids and their conversion to retinol are influenced by the following factors: Species of carotene; molecular Linkage; Amount of carotene in a meal; Matrix in which the carotenoid is incorporated; Absorption modifiers; Nutrient status of the host; Genetic factors; Host-related factors and Interactions (SLAMANGHI). Studies are required to quantify the impact of these factors, especially of the matrix, host-related factors and absorption modifiers.
CONCLUSIONS: The effectiveness of carotene-rich foods in improving vitamin A status and ways of improving carotene bioavailability need further investigation.