The task has been conducted by the VKM Panel on Nutrition, Dietetic Products, Novel Food and Allergy.

The Norwegian Food Safety Authority asked VKM to categorise the amino acids into low, moderate or high risk groups. The three categories are identified by the following criteria:

• High risk: Direct effect on organs or effect on the central nervous system or 
  increased risk of disease development.
• Moderate risk: Changes in biomarkers with known negative health effects.
• Low risk: Changes in biomarkers without known negative health effects or no 
  known adverse effects.

A broad literature search was conducted in the MEDLINE database. VKM found few relevant studies focusing on potential negative health effects for most of the amino acids. Amino acids have a high bioactive potential, and thus VKM concluded that amino acids that are not included in human studies or that are poorly studied may represent a moderate risk.

No tolerable upper intake levels are established for the individual amino acids. The Panel has suggested the following categories:

• High risk: Histidine, methionine, S-adenosyl methionine and tryptophane.
• Moderate risk: Arginine, asparagine/aspartic acid, leucine, isoleucine, valine*, cysteine*, cystine*, phenylalanine*, glutamate, glycine*, hydroxy-methyl-butyrate*, carnitine, lysine, Nacetyl-L-cysteine*, ornithine*, proline*, serine*, spermidine*, taurine, theanine*, threonine* and tyrosine*.
• Low risk: Beta-alanine, glutamine, glutathione and carnosine.

The Norwegian Food Safety Authority has announced that they will request risk assessments of the amino acids that may represent a high risk according to this grouping. The scientific literature on potential negative health effects from high intakes of amino acids in supplements is in generally scarce.