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Provitamins are converted by the body into active vitamins. Many vitamins have provitamins, such as vitamin A and D. Beta-carotene is the most important provitamin A found in fruits and vegetables. Provitamin B5 can be absorbed through the skin and converted to vitamin B5.
Provitamins are the precursors of vitamins. They are dietary substances that can be converted by normal metabolic processes into active vitamins. Depending on the provitamin and vitamin involved, the conversion process takes place in various parts of the body with different levels of efficiency.
Vitamins themselves are organic nutrients essential for human life in small amounts. Eleven of the 13 vitamins are supplied by food, and two require additional conditions. Vitamin D, for example, is formed within the body upon exposure of the skin to ultraviolet light. Many vitamins also have provitamins, which help provide humans with necessary vitamins through additional dietary channels.
Vitamin A can be obtained directly by eating foods that contain retinol, the preformed vitamin. These foods include animal products and fish, especially livers, and various dairy products, such as whole milk, butter, and cheese. Many people receive their daily vitamin A from an important additional source: provitamin A, also known as cartenoids. Cartenoids can be found in many fruits and vegetables, especially those that are red, orange, yellow, or green.
Not all fruits and vegetables that contain these cartenoid pigments also contain provitamin A, but many do, such as carrots, spinach, turnip greens, and palm oil. Beta-carotene, the most important provitamin A in the diet of most humans, can be found in these vegetables, as well as dark yellow squash, squash, sweet potatoes, tomatoes, broccoli, and beets. Other minor sources of beta-carotene include most fruits, summer squash, zucchini squash, beans, cabbage, corn, peas, and many types of nuts.
Beta-carotene is converted to vitamin A in the human body at about a 40 to 50 percent yield and provides up to half the vitamin A needed by most people. A small amount of fat is needed to stimulate the secretion of digestive juices that induce the absorption of beta-carotene – and dietary vitamin A – in the body. People with intestinal disorders who change or decrease their absorption of dietary fat are less able to absorb vitamin A and beta-carotene.
Another important provitamin is 7-dehydrocholesterol, also known as provitamin D. As stated above, the formation of vitamin D requires ultraviolet light, which acts on the provitamin D to create vitamin D. People living above latitude 45 degrees north or below 45 degrees south latitude you should also get dietary vitamin D, which can be found in egg yolks, butter, oily fish, and fortified margarine, to meet your health needs.
Provitamin B5, or panthenol, is the alcohol form of vitamin B5. When absorbed through the skin, panthenol is converted to vitamin B5. You can then hydrate and heal the skin.
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