How Many Amino Acids Are There?

AMINO ACIDS: Amino acids are organic nutrients that appear in foods and in the human body either as building blocks of proteins or as free amino acids.Amino acids are made of the amino group (NH2), carboxyl group (COOH) and a side chain containing carbon, hydrogen or oxygen; two amino acids (cysteine and methionine) also contain sulfur and one (selenocysteine) contains selenium.

FUNCTION OF AMINO ACIDS: Amino acids are a source of energy; like proteins, they can provide about 4 Calories per gram. In the human body, certain amino acids can be converted to other amino acids, proteins, glucose, fatty acids or ketones. Other functions of amino acids include:

  • Chemical messengers (neurotransmitters) in the nervous system: aspartate, GABA, glutamate, glycine, serine

  • Precursors of other neurotransmitters or amino acid-based hormones:

  • Tyrosine is a precursor of dopamine, epinephrine, norepinephrine and thyroxine

  • Tryptophan is a precursor of melatonin and serotonin and nicotinic acid (vitamin B3)

  • Histidine is a precursor of histamine

  • Glycine is a precursor of heme, a part of hemoglobin

  • Aspartate, glutamate and glycine are precursors of nucleic acids, which are parts of DNA


Food protein containing all 9 amino acids in adequate amounts is called complete or high-quality protein.

ANIMAL FOODS with complete protein include liver (chicken, pork, beef), goose, duck, turkey, chicken, lamb, pork, most fish, rabbit, eggs, milk, cheese (cottage, gjetost, cream, swiss, ricotta, limburger, gruyere, gouda, fontina, edam) and certain beef cuts. Animal foods with incomplete protein include certain yogurts and beef cuts.

PLANT FOODS with complete protein include spinach, beans (black, cranberry, french, pink, white, winged, yellow), soy, split peas, chickpeas, chestnuts, pistachios, pumpkin seeds, avocado, potatoes, quinoa, a seaweed spirulina, tofu and hummus. Common plant foods with incomplete protein: rice (white and brown), white bread (including whole-wheat), pasta, beans (adzuki, baked, kidney, lima, pinto, snap), peas, lentils, nuts (walnuts, peanuts, hazelnuts, almonds, coconut), sunflower seeds, kamut.

AMINO ACID SUPPLEMENTS (FREE-FORM AA): Amino acid supplements contain free-form amino acids, which are not bound to each other so they do not need to be digested, so they are absorbed easier than intact protein from food.Amino acid supplements as “amino acid complex,” “amino acid combination,” “amino blend,” “amino acid chelates” with chromium, magnesium or zinc, amino acids as part of vitamin supplements or as single amino acids are available.

THE USE OF AA IN MALABSORPTION: Individuals who have problem digesting natural proteins from food, for example those with lack of protein-digesting enzymes due to chronic pancreatitis, or those with malabsorption syndromes (short bowel syndrome after partial removal of the small intestine, severe celiac disease, can use oral supplements with mixtures of all 9 essential amino acids as a source of protein.

Total parenteral diet (no food by mouth). Patients in hospitals who cannot or should not take food by mouth can get amino acid supplements as the source of proteins by injection into a vein.

There is evidence that branched-chain amino acids (BCAAs) supplements can stimulate muscle recovery and decrease muscle soreness after physical exercise.

There is some evidence that in individuals with sleep disorders amino acids hydroxytryptophan (5-HT) and gamma aminobutyric acid (GABA) taken before sleep can reduce time to fall asleep, sleep duration and quality.

AMINO ACIDS AND YOUR METABOLISM: Amino acids in the human body can be converted into other amino acids, glucose and fatty acids. Every day, some amino acids are broken down and excreted as urea with the urine, so, to maintain the protein balance in the body, you need to regularly consume amino acids by eating foods that contain protein.

AMINO ACID ABSORPTION: When proteins are digested, the resulting amino acids are absorbed in the small intestine. In order for amino acids to be properly absorbed, enough vitamins B12 and C, chromium and sleep is required.

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