Amino acids make up about 75% of the human body. Vital for the production of proteins, amino acids are an important part of a healthy diet, particularly for muscle building and keeping a lean figure. Why do we need amino acids? Unlike fats and starches, amino acids cannot be stored in the body for long periods of time. They deteriorate, so if they are not taken in with relative frequency, the body can have a difficult time functioning at full capacity. While more than 20 different amino acids are needed to form proteins, only the essential amino acids need to be taken in on a daily basis. This can be done through amino acid supplements, but also through certain foods that contain naturally high levels of the essential amino acids your body cannot produce on its own. Here's a list of essential amino acids and the foods where you can get them: Histidine The first essential amino acid can be found in lean meat, particularly ground beef and turkey. It is particularly prominent in cured hams, game meats, and pork products. It is found in both the meat and the skin of these meats. You can also get histidine from eggs, soy, peanuts, parmesan cheese, and sesame. Isoleucine Found in fish, with the highest content percentage in pike, cod, and other North Atlantic seafood, this amino acid is also found in eggs, both the whites and the yolk. Soy protein and tofu also have it. Leucine Leucine is another amino acid found in seafood, particularly fish like pike, cod, and tuna, and in eggs. It is also found in cottage cheese, parmesan, sesame, and game meats, particularly water buffalo and elk. This amino acid is vital for liver and fat tissue construction, as well as construction of connective tissues and muscle health. Lysine Lysine can be derived from most meats, but also from chick peas, lentils, parmesan, quinoa, and soy beans. In terms of meats, chicken and catfish contains large amounts of lysine. Methionine Found in cereal grains, eggs, sesame seeds, mustard seeds, peanuts, and brazil nuts, methionine can also be consumed in fish and other meats. Very little methionine is found in legumes and other vegetables. Racemic methionine is a synthesized amino acid similar to natural methionine, and is often added to pet foods and some processed products. Phenylalanine Interestingly, phenylalanine is found in the breast milk of most mammals, and has an antiseptic and antidepressant effect when consumed. Logically then, you can get it from the skin and meat of most animals and fish, and also in a number of manufactured goods, including diet sodas and other processed foods. Peanuts, eggs, and soy have it, too. Threonine Much like methionine, threonine is found in its highest concentrations in cottage cheese, sesame seeds, poultry, fish, and lentils. Tryptophan Perhaps the most well-known amino acid, tryptophan is plentiful in meats and fish, eggs, sesame and sunflower seeds, chocolate, yogurt, and milk. Though tryptophan supplements were previously questioned due to health concerns, it has returned to many stores in the U.S. and is now sold as a supplement by some pharmacies. Valine Similar to leucine and isoleucine in its chemical composition, valine is found in meats, especially beef, and dairy products. For those who can't consume meat and dairy, supplements are sold at pharmacies, and through supplement and health stores worldwide and online. Some valine is available in soy protein, parmesan, and sesame. Amino acids in other places Though all these amino acids exist in nature, it is not always possible to consume the appropriate foods every day, and truly incorporate amino acids into your daily diet. For this reason, a number of companies make protein powders that contain the necessary amino acids. You can also find them in some sports shakes or drinks that come pre-bottled. Supplements are on the market, which contain all the necessary doses of the essential amino acids.