Vitamin A, identified in 1913, was the first fat-soluble vitamin to be discovered. Vitamin A has also been called the "anti-infective" vitamin due to its role in supporting the activities of the immune system. While retinol (preformed vitamin A), occurs only in foods of animal origin, fruits and vegetables that contain certain carotenoids also provide vitamin A activity. Carotenoids are plant pigments, responsible for the red, orange, and yellow color of fruits and vegetables.
Vitamin A plays a role in a variety of functions throughout the body, including as: vision, immune function, bone metabolism, skin health and reducing risk of heart disease and cancer. Vitamin A helps us to see in dim light and is necessary for proper bone growth, tooth development, and reproduction. Vitamin A is involved in the formation and maintenance of healthy skin, hair, and mucous membranes. Vitamin A stimulates several immune system activities, possibly by promoting the growth, and preventing the stress-induced shrinkage, of the thymus gland. Vitamin A is known to enhance the function of white blood cells, increase the response of antibodies to antigens, and to have anti-viral activity. It is also known that vitamin A is essential for reproductive processes in both males and females and plays a role in normal bone metabolism.
Developing countries such as Ghana have a problem with dietary deficiency of vitamin A and is associated with the high incidence of blindness, viral infections, and child mortality that occurs in poor populations. Vitamin A deficiency mostly affects the health of the skin, hair, eyes, and immune system, though loss of appetite, bone abnormalities, and growth retardation are also associated with inadequate intake of it. A common sign of vitamin A deficiency is hyperkeratosis (a goose bump-like appearance of the skin caused by excessive production of keratin. Due to the important role of vitamin A in supporting the functions of the immune system, individuals with insufficient intake of this vitamin often experience increased susceptibility to viral infections such as measles and chicken pox. Prolonged vitamin A deficiency can lead to night blindness and is a major cause of blindness in developing nations. Vitamin A deficiency is estimated to affect millions of children around the world and almost 250,000-500,000 children in developing countries become blind each year owing to vitamin A deficiency, with the highest occurrence in Southeast Asia and Africa. This has lead to international organizations promoting breast feeding, dietary intake, food fortification, and supplementation. Vitamin A supplementation is practiced in Ghana regularly for children.
Vitamin A mostly comes from animal foods, but some plant-based foods supply beta-carotene, which the body then converts into Vitamin A. Top sources of vitamin A include beef liver, chicken, eggs and fortified milk. Good sources of beta-carotene include carrots, pawpaw, mangoes and some leafy vegetables.
Vitamin A can be lost from foods during preparation, cooking, or storage. To retain vitamin A fruits and vegetables should be eaten raw as much as possible. We should also keep vegetables and fruits covered and refrigerated during storage. Steaming and boiling should be used in preparing vegetables rather than frying. Though supplements are necessary for some people, healthy individuals who eat a balanced diet rarely need supplements.
