Essential nutrient

An essential nutrient is a nutrient required for normal physiological function that cannot be synthesized by the body, and thus must be obtained from a dietary source. Apart from water, which is universally required for the maintenance of homeostasis, essential nutrients are indispensable for the metabolic processes of cells, as well as the proper physiological functions of tissues and organs. In the case of humans, there are nine amino acids, two fatty acids, thirteen vitamins and fifteen minerals that are considered essential nutrients. In addition, there are several molecules that are considered conditionally essential nutrients since they are indispensable in certain developmental and pathological states.

An essential amino acid is an amino acid that cannot be synthesized de novo (from scratch) by an organism, and therefore must be supplied in its diet. Out of the twenty amino acids, nine cannot be endogenously synthesized by humans: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.

Essential fatty acids (EFAs) are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. Only two fatty acids are known to be essential for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid).

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