Essential nutrient

An essential nutrient is a nutrient required for normal body functioning that can not be synthesized by the body.

Categories of essential nutrient include vitamins, dietary minerals, essential fatty acids and essential amino acids.
Many essential vitamins, such as Vitamin C, are also by definition phytonutrients, as they occur in plants.
Different species have very different essential nutrients.
Most essential nutrients are substances that are metabolically necessary but cannot be synthesized by the organism.
Some essential nutrients may be toxic in large doses.
For more information about the topic Essential nutrient, read the full article at Wikipedia.org, or see the following related articles:

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Reference Source : http://www.sciencedaily.com/articles/e/essential_nutrient.htm