Humans have a requirement for a wide variety of different molecules for balanced
metabolism and the maintenance of health. Many of these molecules can be
manufactured within cells under the supervision of genes within the DNA.
However, oxygen, water, all minerals, most vitamins and some proteins and fats
cannot be manufactured by cellular processes and must be acquired from the
environment through breathing, drinking and consuming the cellular components of
plants and animals.
These required substances have been termed “essential nutrients”, as they are
absolutely essential for human life processes to be maintained. The list is extensive
and is growing as we learn more about our physiology.
For normal purposes our food must provide:
Eight essential amino acids (EAAs) from protein: leucine, lysine, isoleucine,
threonine, tryptophan, methionine, valine and phenylalanine. Under certain specific
conditions, such as genetic disorders, other non-essential amino acids may become
essential and are then classified as contingent essential amino acids.
Two essential fatty acids (EFAs): the omega 3 fatty acid alpha linolenic acid and
the omega 6 fatty acid linoleic acid.
Essential vitamins: A, B1,B2,B3,B5,B6,B12, folic acid, biotin, choline, C, D, E and K.
Some of these such as vitamins B12, K and biotin are made by probiotic bacteria in
the gut but not in amounts sufficient for metabolic needs and must be supplemented
by dietary sources. Vitamin D can be made in the skin and so need not necessarily be
provided by the diet – in which case adequate sunlight becomes the essential “nutrient”.
Essential minerals: sodium, potassium, calcium, phosphorus, magnesium, sulphur
and chloride are known as macro-minerals, as they are needed in amounts around or
in excess of 100mg per day for adults.
Iron, manganese, zinc, copper, selenium, chromium, molybdenum and iodine are known
as trace elements as they are essential in less than 100mg amounts per day for adults.
If any of these essential nutrients is missing from the diet for significant periods of
time then physiological disturbances will occur. These are described as nutrient
deficiency disorders and diseases and can be treated by conventional medical techniques,
for example thyroid goitre due to iodine deficiency.
Sub-clinical nutrient deficiency describes a state where a person may have not quite
enough of a given nutrient, iodine for example, for their metabolic needs but not such
a severe deficiency that would provoke a clinical illness such as thyroid goitre. In the
case of iodine such a sub-clinical deficiency might affect mental and physical growth,
metabolism, reproduction and immunity.
Other sub-clinical essential nutrient deficiencies will provoke a variety of physiological
conditions and symptoms depending on the circumstances of the individual.
For further reading about essential nutrients please visit The Linus Pauling Institute.
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