Vitamin A is an essential nutrient obtained through diet, either as retinol from animal products or as provitamin A carotenoids, although mainly from plant products. The contribution of the provitamin A carotenoids depends not only on the amounts of fruits and vegetables consumed and on their proportion with respect to retinol intake from animal sources, but also on the bioavailability and capacity of conversion into retinol of the carotenoids consumed.

The evaluation of the suitability of the diet or the risk associated with excessive or inadequate vitamin A intakes are based in the assessment of nutritional status, using biochemical markers (retinol in serum/plasma, the gold standard) or dietary estimation. Data on nutritional status based on food intake are highly useful for decision-making in the public health setting and in the context of epidemiological studies. However, its validity is limited for several reasons related to food intake assessment, and the way in which data are presented in the food composition table, as well as how vitamin A activity is measured (retinol equivalents, RE or retinol activity equivalents, RAE), among others. Current assumptions about RAE or RE provided for the major provitamin A dietary carotenoids (β-carotene, β-cryptoxanthin, α-carotene), based on its bioavailability from foods, consider β-carotene as major contributor to the vitamin A intake and that the other two provitamin A carotenoids have the same bioavailability and potential for conversion to retinol, which is half that of β-carotene. However, there is a growing research showing that the use of RAE or RE could lead to the underestimation of the contribution of β-cryptoxanthin and of α-carotene. Among them, there are intervention studies involving foods rich in β-cryptoxanthin that lead to better serum retinol responses than β-carotene supplements and also bioaccessibity studies in which β-cryptoxanthin seems to be more efficiently absorbed and converted into retinol than the carotenes (depending on the type of food).

The aim of this Special Issue is to encourage the submission of original research or reviews of scientific literature on the intake of vitamin A broken down into its different components (retinol, β-carotene, α-carotene, β-cryptoxanthin) in representative groups, as well as on studies to assess the bioavailability and the capacity of conversion into retinol that could contribute to answer the question of whether expressions of vitamin A intake in terms of RAE or RE reflect its dietary intake in the population.

Dr. Begoña Olmedilla-Alonso
Dr. Elena Rodríguez-Rodríguez
Guest Editors

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• provitamin-A carotenoids
• bioavailability from food and food supplements
• bioaccessibility
• bioconversion
• human health
• nutritional status
• dietary markers