Nutrients

Amino acids (Protein building blocks)

Amino acids are the 20 building blocks (molecular units) of protein and act as intermediates in metabolism. All proteins are various compositions of twenty-one specific naturally occurring amino acids. The amino acids that are found within proteins convey a vast array of chemical versatility. The precise amino acid content, and the sequence of those amino acids, of a specific protein, is determined by the sequence of the bases in the gene that encodes that protein.

The chemical properties of the amino acids of proteins determine the biological activity of the protein. Proteins not only catalyse most of the reactions in living cells, but they also control virtually all cellular processes. Proteins contain, within their amino acid sequences, the necessary information to determine how that protein will fold into a three-dimensional structure and the stability of the resulting structure. .

Humans can produce some amino acids whilst the others must be supplied in the food. In order to produce some amino acids, the body needs a combination of some that it can manufacture and some that must be consumed.

Failure to consume enough of even one amino acid results in degradation of the body’s proteins leading to breakdown of cellular processes in the body. The distinction between essential and non-essential amino acids is increasingly blurred as more discoveries are made about proteins. As it turns out, we now know that under certain circumstances we can also become deficient in the so-called non-essential amino acids in the same way we can become deficient in essential amino acids. For instance, people with malabsorption syndromes, certain metabolic disease or lacking in vitamin B6 (pyridoxine) may not produce enough non-essential amino acids such as to meet their bodily requirements.

Unlike fat and starch, the human body does not store excess amino acids for later use; the essential amino acids must be in the food every day. Plants must be able to make all the amino acids. Humans do not have all the enzymes required for the biosynthesis of all of the amino acids.

Essential amino acids that must be consumed

  1. Isoleucine
  2. Leucine
  3. Lysine
  4. Methionine
  5. Phenylalanine
  6. Threonine
  7. Tryptophan
  8. Valine

The other nonessential amino acids may become essential to a particular individual through an inborn error of metabolism. If an enzyme, necessary for the manufacture of a particular amino acid by the body is absent, that amino acid becomes an essential requirement of the diet. Nonessential amino acids can also become essential during disease, stress or when taking powerful medications when there is either increased need and/or increased breakdown of them.

Amino acids that are essential to certain individuals

  1. Arginine (children)
  2. Cysteine (premature babes)
  3. Histidine (children)
  4. Taurine (premature babies and infants)

NOTE: When the body synthesises protein, ammonia is formed in the liver as a waste product and too large amounts of protein in the diet can result in too much ammonia being formed, and in so doing placing extra stress on the liver and kidneys to flush it out the body. For more information see the Protein page.

Hundreds of amino acids make up the hormones and neurotransmitters that are produced by the body which control all the essential processes. All natural foods sourced from plants and animals contain varying amounts of amino acids.

Amino acids grouped according to the characteristics of the side chains

Burn patients require more amino acids because of oozing wounds, while one type of schizophrenic may have a recently expressed inborn error of metabolism which dictates the need for less wheat gluten or serine.  Certain cancers can be starved by withholding their ‘favourite’ amino acids. For example, melanomas consume excessive phenylalanine and tyrosine; reducing these two amino acids in a cancer patient’s diet can slow tumour growth. The understanding and manipulation of required amino acids in the diet is essential in maintaining health and controlling disease.

Around 10,000 different proteins may exist in a single cell of the body. Each one requires a different arrangement of amino acids. To make protein, cells must have all the needed amino acids available simultaneously. Therefore, the first important characteristic of protein in the diet, with respect to protein, is that it should supply at least the eight essential amino acids for the synthesis of others, to make proteins.

If one amino acid is supplied in an amount smaller than needed, the total amount of protein that can be synthesised from others will be limited. It is impossible to produce a partial protein. Only complete ones can be made. A diet that contains an imbalance of amino acids is a diet containing poor protein quality. When the body attempts to use the amino acids supply from such a diet, it wastes many amino acids. In the absence of one, it cannot use the others and it has no place to store them.

Types of proteins made from amino acids

The body makes five types of proteins from different combinations of amino acids.

  1. Antibody: These bind to specific foreign particles, such as viruses and bacteria, to protect the body. 
  2. Enzyme: These carry out almost all of the thousands of chemical reactions that take place in cells. They also assist with the formation of new molecules by reading the genetic information stored in DNA.
  3. Messenger: Messenger proteins, such as some types of hormones, transmit signals to coordinate biological processes between different cells, tissues and organs.
  4. Structural component: These proteins provide structure and support for cells. On a larger scale, they also allow the body to move. 
  5. Transport/storage: These proteins bind and carry atoms and small molecules within cells and throughout the body.

For the best natural food sources and in-depth information see each individual amino acid below:

Associated subjects

“Nature cures not the physician…” Hippocrates 460 BC

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