For an element to be considered an essential nutrient, it must meet specific scientific criteria. These criteria ensure that the element is absolutely necessary for the life and health of an organism, not just beneficial.
While the concept applies to all living things, the most clearly defined scientific criteria come from plant biology (botany), known as Arnon's criteria of essentiality.
Here are the primary criteria used to determine if a nutrient is essential:
* Necessity for Life Cycle: The organism cannot complete its normal life cycle—which includes growth, development, and reproduction (like producing seeds in plants)—without this specific element.
* Specific and Irreplaceable Role: The function of the element is unique. No other element can substitute for it to perform the same physiological or biochemical function.
* Direct Involvement in Metabolism: The element is directly involved in the organism's metabolic processes. It is not just merely present or acting indirectl…