What does it mean when an amino acid is essential, conditionally essential or non-essential?

Our bodies are made up of proteins.  Protein is made up of 20 different amino acids.  Of those 20 amino acids, 9 are essential and the rest are either conditionally essential or non-essential. The verbiage can be misleading; non-essential does not mean that those amino acids are not essential nutrients. Non-essential amino acids are still necessary for good health. They are called non-essential because our bodies can synthesize them, whereas essential amino acids must be obtained through diet because our bodies cannot produce them. It is not necessary to consume essential and non-essential amino acids at every meal, but what is important is to get a balanced intake of essential and non-essential amino acids throughout the day.

Essential amino acids, also known as indispensable amino acids, are those that the body cannot synthesize and must be supplied through diet. These essential amino acids are precursors to neurotransmitters and aid in digestion, regulate the body’s metabolic processes, help to make hormones and antibodies which are needed for the immune system, and they help to transport oxygen throughout the body. 

• Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

Non-essential amino acids are those amino acids that can be synthesized by the body in adequate quantities. It does not mean that these amino acids are not essential to good health. Non-essential amino acid functions in the body are equally as important as essential amino acids; they maintain the proper functioning of joints, help to form neurotransmitters, essential for proper functioning of the central nervous system, protective to cardiovascular health, aid in digestion and help to boost the immune system – just to name a few of their functions.

• Alanine, Asparagine, Arginine, Aspartate (Aspartic Acid), Glutamate (Glutamic Acid), Tyrosine, Cysteine, Glycine, Proline, Serine

Conditionally essential amino acids:  Of the 10 non-essential amino acids, 7 of those amino acids become essential when the body does not produce enough to meet the physical requirements of the individual. Conditionally essential amino acids are typically non-essential, except during times of growth, illness and stress and while recovering from intense exercise. 

• Arginine, Cysteine, Glutamine, Glycine, Proline, Tyrosine, Serine