Soundharya Subramanian, BSc Clinical Nutrition,
M.Sc. Clinical Nutrition (Student), MMM College of Health Sciences, Chennai, India
Vitamin A is a fat-soluble vitamin which plays a major role in vision, reproduction, growth, and maintenance of epithelial and bone structures. In the body, vitamin A exists as retinol, retinal and retinoic acid. The other two members of the vitamin A family of compounds are retinyl esters and β-carotene. (1)
Sources of vitamin A
- Vitamin A is obtained from the diet through animal (preformed vitamin A) and plant sources (pro-vitamin A) in the form of retinol and carotenoids. (1)
- Retinol is the principal dietary form of vitamin A which are readily absorbed into the body. They are commonly found in liver, meats, eggs, milk products, and fatty fish. (1)
- Carotenoids are lipid-soluble pigments responsible for the colour of a wide variety of fruits and vegetables. They are provitamin A which are subsequently transformed into vitamin A.(3)
- Carotenoids pigments are classified based on their chemical composition as either carotenes (hydrocarbon carotenoids) or xanthophylls (oxygen-containing carotenoids). (3)
- There are about 700 carotenoids in nature, but only about 50 have provitamin activities. Of those 50 compounds, the three most important precursors of vitamin A in humans are α-carotene, β-cryptoxanthin, and β-carotene. β-Caroteneis the most prominent member of the group of carotenoids.(2)
- Carotenoids exist in four forms: beta-carotene, alfa-carotene, gamma-carotene, and beta-cryptoxanthin that can each be converted to retinol (vitamin A). The other carotenoids are lycopene, lutein, and zeaxanthin which function as antioxidants, but are not converted to retinol (vitamin A). (3)
- Alpha-carotenes & Beta-carotenes: They are yellow, orange and greens pigments of fruits and vegetables.(4)
- Yellow-orange vegetables: Carrots, Sweet potatoes, Pumpkin, Winter squash. (4)
- Dark-green-vegetables: Broccoli, Green-beans, Green peas, Spinach, Turnip greens, Collards, Leaf lettuce and Avocado. (4)
- Beta cryptoxanthin: Foods that are rich in beta-cryptoxanthin include tangerines, persimmons and oranges, corn, and peaches. (4)
- Lycopene: They are red pigments found in grapefruit, watermelons, and papaya and tomatoes. (4)
- Lutein and zeaxanthin: Lutein and zeaxanthin are the most common xanthophylls in green leafy vegetables like kale, spinach, broccoli, peas and lettuce and egg yolks.(4)
- Srilakshmi, B. (2006). Nutrition Science. New Age International.
- Nieves, J. W. (2013). Alternative Therapy through Nutrients and Nutraceuticals. In Osteoporosis (pp. 1739-1749). Academic Press.
- Mander, L., & Liu, H. W. (2010). Comprehensive natural products II: Chemistry and Biology(Vol. 1). Elsevier.
- Caballero, B., Trugo, L. C., & Finglas, P. M. (2003). Encyclopaedia of food sciences and nutrition. Academic. Pg. 927 – 936.