This review will discuss some common methods used to study vitamin absorption and the proposed mechanisms of absorption, and will conclude with a section about dietary regulation. Vitamins are essential organic nutrients. Minute amounts of vitamins participate in three general functions of the body: growth, protection and energy regulation. There are a total of 16 vitamins. Four are fat-soluble: vitamins A, D, E and K. The rest are water-soluble. Eight vitamins are in the B complex: RIBOFLAVIN (B1), THIAMIN (B2), NIACIN (B3), VITAMIN B6, and vitamin B12, FOLIC ACID, PANTOTHENIC ACID and BIOTIN. VITAMIN C is also water-soluble but is not considered a B vitamin, which functions as enzyme helpers (coenzymes). Two additional substances that have vitamin functions are known as CHOLINE and INOSITOL. Vitamins either cannot be synthesized by the body or they cannot be made in adequate amounts, so they must be supplied by the diet. As examples of the latter, vitamin D can be made in the skin when exposed to sunlight, while some niacin can be made from the amino acid tryptophan. The intestine is a source of BIOTIN, pantothenic acid and VITAMIN K; these are supplied by "friendly" intestinal bacteria, though the exact amounts supplied are difficult to assess. The term '"vitamin" dates from 1912, and the first vitamin to be isolated was vitamin A in 1913. Thiamin was discovered in 1926, vitamin K in 1929, and vitamin C in 1932. Vitamin B12 was the most recent vitamin to be discovered (1948). Before a compound can be classified as a vitamin, it must be proven that animals must obtain the compound from their diet. Typically, scientists test lab animals such as mice with a diet free of the test substance, together with a dose of antibiotics to eliminate intestinal bacteria. Vitamin utility is a scientific/medical topic that appears to be pursued as ardently by the lay public as by scientists and medical practitioners. A group of epidemiologists evaluates the effects on health of vitamin intake in the natural diet and by supplementation. The role in ocular disease, cancer of the breast or colon, and cardiovascular disease are a few of the concerns. The results and recommendations concerning dietary vitamin intake will likely continue to change. However, the processes by which dietary vitamins are delivered from intestinal chyme to the blood are more certain. The concept of homeostasis might apply to several of the vitamins as it does to minerals, water, etc.
Keywords: Water-soluble vitamins, fat-soluble vitamins, vitamin deficiency, Supplements.
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