Essential nutrient

An essential nutrient is a substance required for normal growth, maintenance, or function that an organism cannot synthesize in sufficient amounts and must obtain from its environment.

Nutrient: A substance an organism obtains and uses for energy, growth, maintenance, or regulation. Essential nutrients are the subset of nutrients that must come from outside the organism.
Dietary reference intake: A set of quantitative nutrient-intake standards used to plan and assess diets. These standards translate essentiality into recommended intake levels for populations and individuals.
Essential amino acid: An amino acid that an organism cannot synthesize in sufficient amounts and must obtain from its diet. Humans require nine amino acids from food because their metabolic pathways cannot make enough.
Nutrient deficiency: A state in which inadequate intake or availability of a nutrient impairs normal function. Deficiency is the consequence of failing to obtain enough of an essential nutrient.
Metabolism: The network of chemical reactions that sustains life by transforming matter and energy. Metabolic pathways determine which required substances an organism can synthesize.
Recommended dietary allowance: The average daily nutrient intake estimated to meet the needs of nearly all healthy people in a specified group. It sets a practical target for intake of essential nutrients.
Essential fatty acid: A fatty acid that an organism cannot synthesize in sufficient amounts and must obtain from its diet. Humans must obtain linoleic acid and alpha-linolenic acid from food.
Nutrient toxicity: Harm caused by excessive exposure to a nutrient or its biologically active forms. An essential nutrient can still become harmful when intake exceeds the body’s capacity to handle it.
Biosynthesis: The enzyme-driven production of complex molecules by living organisms. A nutrient becomes essential when biosynthesis cannot meet the organism’s needs.
Dietary supplement: A product intended to add nutrients or other substances to the diet. Supplements can provide essential nutrients when food intake is inadequate or needs are elevated.

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