Meeting the Vitamin A Requirement: The Efficacy and Importance ofβ-Carotene in Animal Species

Abstract

Vitamin A is essential for life in all vertebrate animals. Vitamin A requirement can be met from dietary preformed vitamin A or provitamin A carotenoids, the most important of which is β-carotene. The metabolism of β-carotene, including its intestinal absorption, accumulation in tissues, and conversion to vitamin A, varies widely across animal species and determines the role that β-carotene plays in meeting vitamin A requirement. This review begins with a brief discussion of vitamin A, with an emphasis on species differences in metabolism. A more detailed discussion of β-carotene follows, with a focus on factors impacting bioavailability and its conversion to vitamin A. Finally, the literature on how animals utilize β-carotene is reviewed individually for several species and classes of animals. We conclude that β-carotene conversion to vitamin A is variable and dependent on a number of factors, which are important to consider in the formulation and assessment of diets. Omnivores and herbivores are more efficient at converting β-carotene to vitamin A than carnivores. Absorption and accumulation of β-carotene in tissues vary with species and are poorly understood. More comparative and mechanistic studies are required in this area to improve the understanding of β-carotene metabolism.

Vitamin A administration in lizards during tail regeneration determines epithelial mucogenesis and delays muscle and cartilage differentiation

“…Information on the concentration and metabolism of vitamin A in reptilian tissues, especially in the liver as Vitamin A2 (dehydroretinol), are scanty but appear similar to the known data on the metabolism of the vitamin in mammals (Green & Fascetti, ; San‐Jose, Granado‐Lorencio, & Fitze, ). According to a max safe dose of 4.5 μg/g body weight (https://todaysveterinarypractice.com/hypervitaminosis-a-in-reptiles/), the injected vitamin A dose of approximately 20 μg/g body weight appears four to five times higher, justifying a toxic effect in lizards after few days of treatment.…”

Germplasm of Brazilian winter squash (Cucurbita moschataD.) displays vast genetic variability, allowing identification of promising genotypes for agro-morphological traits

“…The main biological functions of components such as α - and β -carotene are their pronounced pro-vitamin A activity [74, 75], and a series of bioactive functions, especially antioxidant activity [76, 77]. Along with its bioactive functions, C. moschata brings together fundamental characteristics for biofortification programmes, such as high production potentials and profitability, high efficiency in reducing deficiencies in micronutrients in humans, and good acceptance by producers and consumers in the growing regions [10].…”

The Role of Vitamin A in Wound Healing

“…23 Vitamin A toxicity occurs with long-term ingestion of 3-4 times the recommended daily allowance; meanwhile, β-carotene does not appear to have any toxic effects, secondary to decreased conversion to vitamin A in the setting of excess βcarotene. 24,25 The efficiency of the conversion of β-carotene to vitamin A is also highly dependent on vitamin A status; therefore, β-carotene is a relatively safe way to increase vitamin A status without risking toxicity. For reference, the general conversion ratio of dietary β-carotene to vitamin A is 12 µg of β-carotene required to form 1 µg of retinol.…”

“…For reference, the general conversion ratio of dietary β-carotene to vitamin A is 12 µg of β-carotene required to form 1 µg of retinol. 24 Excess dietary intake of preformed vitamin A has teratogenic effects, specifically associated with cranial-neuralcrest defects. 26 Among a study of 22,748 women, the ratio of such defects was 3.5 for those mothers who consumed >15,000 IU of preformed vitamin A per day compared with those who consumed 5000 IU or less.…”

“…The efficiency of the conversion of β‐carotene to vitamin A is also highly dependent on vitamin A status; therefore, β‐carotene is a relatively safe way to increase vitamin A status without risking toxicity. For reference, the general conversion ratio of dietary β‐carotene to vitamin A is 12 µg of β‐carotene required to form 1 µg of retinol …”