Amino acids are more than just a sports supplement -- they're the molecular chains that bind together to form large, complex protein molecules. When you eat protein, your digestive system breaks the big molecule down into its constituent amino acids and adds more molecules to each one to create a different set of amino acids. Together, they are responsible for your growth and play a role in almost every one of the body's functions. Your risk of a deficiency is low as long as you eat enough protein.
Essential Amino Acids
The essential amino acids are the ones your body cannot make, so you must get them through your food. According to the World Health Organization, healthy adults need 39 mg of leucine, 20 mg of isoleucine, 26 mg of valine, 4 mg of tryptophan, 10 mg of histidine, 30 mg of lysine, 10 mg of methionine, 15 mg of threonine and 25 mg of phenylalanine per kilogram of body weight per day. A deficiency in any one amino acid can inhibit muscle repair and stunt growth, and it can cause a deficiency in other amino acids that your body makes itself.
Conditional Amino Acids
You only need conditional amino acids during certain life stages or under special circumstances. For example, you need 4 mg of cysteine per kilogram of body weight per day, but cysteine is a byproduct of the breakdown of methionine, so supplementation is considered necessary only when methionine is deficient. Similarly, tyrosine is a byproduct of phenylalanine breakdown, so you only need to consume it if you don't get enough phenylalanine. Other conditional amino acids include glutamine, which endurance athletes supplement to protect their immune system, arginine, glycine, serine, proline and ornithine. Everyone's need for these amino acids varies according to age, climate, diet and overall health.
Nonessential Amino Acids
Your body makes its own nonessential amino acids, so you don't have to get them from food. These include asparagine, aspartic acid, glutamic acid and alanine. Basically, the essential amino acids provide a scaffolding over which your body adds molecular materials to produce the nonessential amino acids. Thus, when you are deficient in the essential amino acids, your body won't have the raw material to make the nonessential ones. This usually only occurs during severe or prolonged illness or in cases of highly restricted diet.
Meeting Your Needs
The WHO suggests a daily protein intake of 0.83 g per kilogram of body weight per day for most adults. Meat, fish and poultry are complete proteins, meaning they contain all essential amino acids, so including them in your diet reduces your risk of an amino acid deficiency. Soy is also considered a complete protein and is an important one for vegetarians, but it has a low methionine content. If soy is the main protein in your diet, add sesame seeds to your diet to boost your methionine levels. Whole grains and legumes also contain protein, but it is incomplete protein. If you rely on plant-based protein, eat as wide a variety as possible to make sure you get all of the essential amino acids.
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