Vitamins

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Vitamins are a group of organic food substances or nutrients found only in living things, plants and animals. The word vitamin is derived from the term "vitamine", which was first used in 1912 by Dr. Casimir Funk, a Polish biochemist, in reference to substances that were ‘vital’ to life and contained an ‘amine’.

Vitamins are divided into two classes based on their solubility. There are fat-soluble vitamins which include vitamin D, vitamin E, vitamin A, and vitamin K and the other class is of water-soluble vitamins such as folate (folic acid), biotin, vitamin B6, niacin, thiamin, riboflavin, pantothenic acid, and vitamin C (ascorbic acid). Fat-soluble vitamins contain only carbon, hydrogen, and oxygen while water-soluble vitamins contain these three elements plus nitrogen and at times, sulfur. Fat-soluble vitamins can be stored in the body whereas water-soluble vitamins cannot be stored in the body.

Vitamins are essential in small amounts for normal metabolism and good health. Although vitamins and minerals have no calories and are not an energy source, they do assist in metabolizing nutrients in food and are invaluable in keeping the body running smoothly. Vitamins make it possible for other nutrients to be digested, absorbed and metabolized by the body. They are required to do many things and their excess or depletion can lead to acute and chronic disease.

Functions of vitamins in human body

Vitamins promote normal growth, provide proper metabolism, ensure good health and protect against certain diseases. Vitamins are required by the body in small amounts for metabolism, to protect health and for proper growth in children. Vitamins assist in the formation of hormones, blood cells, nervous-system chemicals, and genetic material. Vitamins mainly serve as catalysts for certain reactions in the body. They combine with proteins to create metabolically active enzymes that in turn produce hundreds of important chemical reactions throughout the body. The fundamentals of cells depend greatly upon vitamins. Vitamins are responsible for keeping cells strong, binding tissues, fighting infections, etc. Without vitamins, our cells would not function properly and thus our organs would suffer and eventually we would no longer be able to survive. Vitamins help regulate metabolism, help convert fat and carbohydrates into energy, and assist in forming bone and tissue.

Sources of vitamins

Most of the vitamins can be found in plant and animal sources. They can also be chemically synthesized.

Vitamin dietary reference intakes, recommended dietary allowances

Insufficient vitamin intake will lead to a number of vitamin deficiency diseases. However, high doses of vitamins should be regarded as drugs rather than supplements, which will cause some potential health risks. To keep people informed of the correct nutrition intake, the Food and Nutrition Board of the National Academy of Sciences/National Research Council publishes the Recommended Daily Allowances (RDA) for vitamins and other nutritional supplements based on scientific researches and clinical findings.

These are the amounts of nutrients and calories an individual is recommended to consume daily to maintain good health for the majority of populations. The Dietary Reference Intakes (DRIs) are a comprehensive set of nutrient reference values for healthy populations that can be used for assessing and planning diets. DRIs replace previously published Recommended Nutrient Intakes (RNIs). Estimated Average Requirement (EAR) is the average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular life stage and gender group. RDA is the average daily dietary nutrient intake level sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group. Adequate Intake (AI) is the recommended average daily intake level based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate - used when an RDA cannot be determined. Tolerable Upper Intake Level (UL) is the highest average daily intake level that is likely to pose no risk of adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects may increase.

Vitamin deficiencies and human health

Vitamins are of vital importance in maintaining human health. Deficiencies of most of the vitamins will result in corresponding diseases. A deficiency of vitamin A can cause retarded skeletal growth, night blindness, various abnormalities of the skin and linings of the genitourinary system and gastrointestinal tract. Thiamin deficiency can lead to muscular weakness, leg cramps, slow heartbeat, and irritability, defective hydrochloric acid production in the stomach and consequent digestive disorders. Riboflavin deficiency can cause inflamed tongue, inflammation and ulcers in the mouth, Dandruff, weakness, abnormal blood vessel growth on the sclera, and low blood counts. A niacin deficiency often leads to a chronic illness called pellagra. Vitamin B5 deficiency causes depression, personality changes, and heart problems. Vitamin B6 deficiency can cause impaired immunity, skin lesions, and mental confusion.

A deficiency of vitamin B12 (cobalamin) deficiency can cause pernicious anemia. An inositol deficiency could be a contributing cause of abnormal platelet aggregation, and alcoholism. Patients with systemic carnitine deficiency have a progressive neuromuscular disorder with nausea and vomiting. A deficiency in PABA may cause fatigue, irritability, depression, nervousness, headache, constipation and other digestive disorders. A lack of vitamin C leads eventually to scurvy. In children, vitamin D deficiency is called rickets. Vitamin E deficiency affects the central nervous system and causes muscle weakness, loss of muscle mass, abnormal eye movements, impaired vision, and unsteady gait. Biotin deficiency results in fatigue, depression, nausea, muscle pains, hair loss, and anemia. Symptoms of vitamin K deficiency include easy bruisability, epistaxis, gastrointestinal bleeding, menorrhagia and hematuria. Folic acid deficiency during pregnancy increases the risk for neural tube defects.

Vitamin overdose, side effects and toxicity

Overdose of certain vitamins may cause some side effects. Therefore, the supplementation of vitamins should be safely dosed with the guides of a reliable medical instruction. Excessive intake of vitamin A can be harmful to bones and skin, causing weakness and brittleness. Large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Vitamin B6 toxicity can damage sensory nerves. High doses of PABA can cause blood sugar to drop. There is a high health risk associated with consuming too much vitamin D.

Some of the most important vitamins are:

Fat soluble vitamins

Water Soluble Vitamins