Amino Acids: The Building Blocks of Protein

The following table shows all 20 proteinogenic amino acids with their usual classification. Essential amino acids cannot be made by the body itself and must be taken in regularly with food. Semi-essential amino acids, also called conditionally essential, can in principle be produced by the body, but in phases of growth, stress or illness its own production is sometimes not enough. Non-essential amino acids can be synthesised by the healthy body in sufficient amounts.

The assignment of individual amino acids to the semi-essential group is not always handled consistently in the specialist literature, as actual requirements depend heavily on age, health status and stress. For practical nutrition, what matters most is that a varied diet with different protein sources supplies all 20 amino acids in sufficient amounts.

The fundamental importance of amino acids for building body protein, for enzymes, hormones and the immune system is scientifically well established and undisputed. The role of individual amino acids such as leucine in stimulating muscle protein synthesis after training is also considered comparatively well supported.

For many specific additional claims around free amino acid products, for example on fat loss, mood or anti-ageing effects, the evidence is mixed to thin. Positive findings often come from small studies, from studies in particular groups of people or from animal experiments, which cannot simply be transferred to healthy, adequately nourished adults. If you already get enough protein from food, you should therefore treat specific advertising claims for individual products with some caution, without questioning the fundamental importance of amino acids for the body.

How many amino acids are there?

In total, 20 amino acids are proteinogenic, that is, the ones from which human protein is built. Nine of these are considered essential, and others are classed as semi-essential depending on circumstances.

Can you take in too many amino acids?

With a balanced diet within the usual protein requirement ranges, this is generally unproblematic for healthy people. With kidney disease or very high additional intake through supplements, medical advice beforehand is recommended.

Is a normal diet enough to cover all amino acids?

With a varied diet containing enough protein from different sources, the supply of all essential amino acids is generally covered. One-sided diets or a very low calorie intake can increase the risk of an insufficient supply.

Are plant protein sources at a disadvantage when it comes to amino acids?

Individual plant foods are often weaker in certain amino acids than animal sources, but this can be balanced out well by combining different plant foods over the day.

What do the abbreviations BCAA and EAA stand for?

BCAA stands for branched-chain amino acids, meaning leucine, isoleucine and valine. EAA stands for all nine essential amino acids together. You can find more in the guides to BCAA and EAA.

Are free amino acids better than protein from food?

Not better in general, but mainly available faster, since they do not first have to be digested. For your total daily supply, the overall amount of protein you take in matters more than the form of the amino acids.

• Isoleucine: branched-chain amino acid and part of the BCAA, with a role in the energy metabolism of muscle.
• Valine: the third BCAA amino acid, important for muscle tissue and nitrogen balance.
• Methionine: sulphur-containing essential amino acid and starting material for other compounds made by the body.
• Threonine: essential amino acid important for connective tissue and mucous membranes.
• Tryptophan: essential amino acid and precursor of serotonin.
• Phenylalanine: essential amino acid and precursor of tyrosine.
• Histidine: essential amino acid important for tissue proteins.
• Glycine: simplest amino acid and an important building block of collagen.
• Lysine: essential amino acid important for connective tissue and the immune system.
• Leucine: branched-chain amino acid with a special role in muscle protein synthesis.
• EAA: an overview of combination products with all nine essential amino acids.
• BCAA: an assessment of the branched-chain amino acids leucine, isoleucine and valine.
• L-arginine: semi-essential amino acid with a role in nitrogen balance and blood flow.
• L-citrulline: amino acid from which the body can form arginine, among other things.
• Glutamine: most abundant amino acid in the blood, important for the gut and immune system.
• Taurine: sulphur-containing compound often found in sports drinks.
• Tyrosine: precursor of important messenger substances, formed from phenylalanine.
• Beta-alanine: amino acid from which the body forms carnosine.
• Carnosine: compound of beta-alanine and histidine with a role in muscle metabolism.
• Aspartic acid: non-essential amino acid with a role in nitrogen metabolism.
• GABA: compound formed from glutamic acid with a role in the nervous system.

• Amino acids for muscle building: what role amino acids realistically play in training progress.
• Amino acids and recovery: how amino acids can support recovery after training.
• Amino acids and the immune system: links between amino acid supply and the body's defences.
• Amino acids for weight loss: a factual assessment of what contribution amino acids can make in a diet.
• Amino acids as natural fat burners: putting such advertising claims in context using the evidence.
• Amino acids against wrinkles: which amino acids are associated with collagen formation and skin structure.
• Healthy hair through amino acids: the importance of amino acids for hair structure and hair growth.
• Amino acids for people with diabetes: what people with diabetes should watch for with amino acid products.
• Amino acids for boosting potency: an honest assessment of such claims around arginine and others.
• Sensible supplementation with amino acids: when amino acid products can be a useful addition.
• The most important amino acids for effective training: an overview of amino acids relevant to training.
• Colostrum as a natural source of amino acids: an assessment of colostrum as a dietary supplement.