Health assessment of amino acids

Nine proteinogenic amino acids are indispensable (essential) for humans: Isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine for adults and histidine for infants. As the body cannot synthesise these amino acids itself, they must be taken in with food. The proteinogenic amino acids tyrosine and cysteine, which can be synthesised from phenylalanine and methionine respectively, occupy a special position.

Amino acids are found in a large number of foods, mainly in bound form as components of proteins and to a lesser extent as free amino acids. In free form, amino acids are involved in the flavour of foods. For example, the tasteless amino acid glutamic acid or its salt enhances the flavour of many foods. If the intake of essential amino acids is insufficient, the body's own protein formation is not possible.

High additional intakes of individual amino acids can cause undesirable effects.

In cases where there is a need for official assessment of the addition of free amino acids to foods, the BfRshort forGerman Federal Institute for Risk Assessment prepares health assessments. As a member of the DGE's Sports Nutrition Working Group, the BfRshort forGerman Federal Institute for Risk Assessment was involved in the development of a position paper on the physiological effects of protein intake in sport.

Amino acids are carboxylic acids (= organic compounds with one or more carboxyl groups (-COOH)) that carry one or more amino groups (-NH2). This broad definition covers a large number of substances that occur naturally in organisms; however, the term is often used to refer only to the most important group by far, the proteinogenic amino acids (L-amino acids). This term summarises the amino acids that serve as building blocks of naturally occurring peptides and proteins (protein) and are directly incorporated into these. In humans, these are 20 amino acids. All proteinogenic amino acids have the amino group on the carbon atom nearest to the terminal carboxyl group (C atom). The very differently structured side chain residues determine the specific properties of the individual amino acids.

The greatest importance of amino acids for the organism lies in their function as protein building blocks. Proteins are essential functional and structural components of all body cells. Furthermore, amino acids contribute to the fulfilment of the daily energy requirement via protein and amino acid degradation. Various free proteinogenic amino acids serve as messenger substances in the nervous system. Proteinogenic amino acids also serve as starting substances for the body's own substances or are involved in their formation (e.g. for messenger substances, bile salts, thyroid hormones). All other amino acids found in the human body (e.g. ornithine, γ-aminobutyric acid) can also be formed from proteinogenic amino acids.

The amino acid requirement results primarily from the need for essential amino acids. The daily intake recommendations for adults range from 4-5 mgshort formilligram per kilogramme (kgshort forkilogram) of body weight (bw) for tryptophan to 39-42 mgshort formilligram/kgshort forkilogram bw for leucine. The amino acid requirement is covered by the daily protein intake (for adults 0.8 g/kgshort forkilogram body weight).