Amino acids are the compounds that attach together to form proteins. When you consume proteins, your digestive system breaks them down into amino acids which are used to repair tissues, break down food and keep you healthy. Your body also has the ability to make some of the amino acids.
Amino Acid Groups
There are a total of 20 amino acids that are divided into groups based on whether or not your body has the ability to make them. Amino acids that your body cannot make are deemed essential amino acids. They are essential because you must consume them through your diet. The essential amino acids include leucine, isoleucine, lysine, histidine, arginine, threonine, methionine, valine, phenylalanine and tryptophan. The nonessential amino acids, which are the amino acids your body can make, include glutamine, glutamic acid, alanine, glycine, proline, asparagine, aspartic acid, cysteine, serine and tyrosine.
Classes
Amino acids are also categorized by class. There are four different classes of amino acids, each class determined by the amino acid side chain. The nonpolar, or hydrophobic, amino acids include glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan and proline. The polar, or hydrophilic, amino acids include serine, threonine, cysteine, tyrosine, asparagine and glutamine.
Some amino acids, like electrolytes, also carry an electrical charge, either positive or negative. The positively charged hydrophilic amino acids include glutamic acid and aspartic acid. The negatively charged hydrophilic amino acids include arginine, lysine and histidine.
Tryptophan
Tryptophan is a nonpolar, hydrophobic, essential amino acid. Infants need tryptophan to grow normally and adults require tryptophan to remain in nitrogen balance. Tryptophan also acts as a precursor to the B vitamin, niacin, and the neurotransmitter, serotonin, which helps regulate your mood. The conversion of tryptophan to niacin relies on adequate amounts of iron, vitamin B6 and riboflavin in the body. Many different foods offer tryptophan. These foods include turkey, chicken, eggs, cheese, milk, nuts, soy, tofu, pumpkin seeds and sesame seeds.
Tryptophan and Sleep
Tryptophan is often associated with sleepiness. This is because when you eat a lot of tryptophan, the levels of serotonin in your brain increase. Serotonin is then converted into melatonin, which regulates your sleep cycle and body clock. When melatonin levels increase, it signals your body to sleep. Stanford University notes that this effect may be the reason why a warm glass of milk is considered a natural sleep aid.
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