Saturday, August 22, 2009
Vitamin A sources can be classified as plant and animal food sources. Plant sources include both fruits and vegetables that contain vitamin A, while animal sources includes meat and poultry derived foods. Animal Sources: In animal foods, vitamin A is found as retinol, one of the most important forms of vitamin A, which is usually converted into retinal and retinoic acid. Some important sources of this include beef, chicken, eggs, fish, cheese and seafoods. Plant Sources: In plants, vitamin A is found as provitamin A carotenoids. Some important carotenoids are carotene (alpha and beta carotene) and cryptoxanthin. Apricot, cantaloupe, mango, orange, apple, watermelon, plum, blackberry, peach and kiwi are some of the fruits that contain vitamin A. Among the vegetables, carrot, pumpkin, broccoli, peas, spinach, sweet potato, turnip, tomatoes, wheat germ, escarole, collards, dandelion green, mustard green, aloe vera etc. are rich sources of vitamin A. However, cooking and storing of these vegetables and fruits may result in substantial loss of vitamin A. Therefore, it is very important to cover them while storing in refrigerators. Raw fruits and vegetables can provide more vitamins than cooked ones, so it is best to eat them raw. While cooking vegetables, it should be kept in mind that steamed or baked vegetables are more likely to retain the essential vitamins than the fried ones. Our bodies need certain essential minerals like zinc and iron for the proper utilization of vitamin A. Zinc is required for the transportation of vitamin A from the storage organ liver to the tissues, while this vitamin plays an important role in the metabolism of iron. Deficiency of vitamin A can trigger a number of diseases in human beings. Its deficiency usually results in night blindness, which can eventually lead to complete blindness. Deficiency of this vitamin can also weaken the human immune system. Studies have revealed that children with mild deficiency of vitamin A are at a greater risk of developing respiratory diseases and diarrhea. Studies have also shown that the presence of vitamin A can decrease the occurrence and severity of measles. So, including sufficient amount of vitamin A-rich foods in your diet, along with iron and zinc is an indispensable prerequisite for living a disease-free, healthy life.
Vitamin A plays an important role in many vital functions of the human body. A well-known function of vitamin A is ensuring healthy vision. Besides, it is also required for bone growth, cell division, and cell differentiation. Vitamin A is also supposed to have enhancing effects on the immune system, as it produces disease-fighting white blood cells (WBCs), including lymphocytes. White blood cells are essential for preventing any kind of infection. Both retinol and retinoic acid play a significant role in embryonic development. Retinoic acid plays an important part in the formation of the heart, eyes, ears and limbs of the embryo. Vitamin A is essential for the healthy lining that covers the urinary, respiratory and intestinal tracts. The outer covering of these body systems provide protection against any infection. Vitamin A is also required for the growth of the thymus and spleen, for healthy tooth enamel and gums, for the repair of tissues and also for the reproductive system. Vitamin A plays a part in protein synthesis and reduces cholesterol.
Vitamin A, commonly known as retinol, is a group of fat-soluble vitamins, that play a crucial role in the smooth operation of many life-sustaining processes. It was discovered in 1917, through the independent efforts of Elmer McCollum at the University of Wisconsin-Madison, and Lafayette Mendel and Thomas Osborne at Yale University. Vitamins are generally classified as water-soluble and fat-soluble. Vitamin A belongs to the latter group, and occurs in different forms. It can be found as alcohol (retinol), aldehyde (retinal), acid (retinoic acid) and also as ester (retinyl palmitate).