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Vitamins are essential for the normal growth and development of humans. For the most part, vitamins are obtained from food, but a few are obtained by other means. For example, microorganisms in the intestine – commonly known as “gut flora” – produce vitamin K and biotin, while one form of vitamin D is synthesized in the skin with the help of natural ultraviolet in sunlight. Humans can produce some vitamins from precursors they consume. Examples include vitamin A, produced from beta carotene, and niacin, from the amino acid tryptophan. Throughout life, vitamins are essential for healthy maintenance of the cells, tissues, and organs, and also enable us to efficiently use chemical energy provided by food as well as help process the proteins, carbohydrates, and fats required for respiration.
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