Essentiality
 

Nutritional Medicine has been practised throughout history and across civilisations, ranging from nutritional aspects of traditional Chinese medicine, the use of ‘healing’ foods such as garlic and onion by the Egyptians, to the Hippocratic physicians of Greece who believed that one health-providing element called ‘aliment’ existed in all foods.

Various experiments and observations over the following two centuries finally lead to the foundation of the concept of ‘essentiality’ of certain nutrients being absolutely necessary for the growth, health and survival of the human species.


The Concept of Essentiality & Conditional Essentiality

The establishment of the essentiality of certain nutritional factors has been pivotal in the progression of nutritional science.

In the 1600's when Sydenham found that iron filings prevented anaemia.
In 1740, Lind, a British naval surgeon, made the observation that citrus fruits prevented scurvy in sailors.
Various experiments and observations over the following two centuries finally lead to the foundation of the concept of 'essentiality' of certain nutrients being absolutely necessary for the growth, health and survival of the human species.

Definition of Essentiality
(Harper et al., 1999. In Modern Nutrition in Health and Disease. Eds Shils et al.)


The criteria for essentiality are defined as follows:

1. The substance is required in the diet for growth, health and survival.
2. Its absence from the diet, or inadequate intake, results in characteristic signs of a deficiency disease and, ultimately, death.
3. Growth failure and characteristic signs of deficiency are prevented only by the nutrient or a specific precursor of it, not by other substances.
4. Below some critical level of intake of the nutrient, growth response and severity of signs of deficiency are proportional to the amount consumed.
5. The substance is not synthesized in the body and is therefore required throughout the lifetime.