Though most of the amino acids needed are manufactured by the body, nine are not; these are known as the essential amino acids — L-histi-dine, L-isoleucine, L-leucine, L-lysine, L-methionine, Lphenylalanine, L-thre-onine, L-tryptophan, and L-valine — and all are provided by proteins in the diet.
The other fifteen not needed in the diet are alanine, arginine, asparginine, aspartic acid, carnitine, cysteine, cystine, glutamic acid, glutamine, glycine, hydroxyproline, ornithine, proline, serine, and tyrosine. The line between essential and nonessential amino acids is fuzzy, as children require arginine for growth and, for adults under such condition as stress to the body (extreme heat, extreme cold, shock, drugs, toxic agents), illness (fever), or pregnancy, any one of the nonessential amino acids, mostly the "branchchain" ones (leucine, isoleucine, valine), can become essential.
Those with allergies, for example, use an excess of histamine in their bodies, which is manufactured from histidine. Genetic problems can also lead to deficiencies.
Complete proteins provide the proper balance of all the amino acids, and these foods include meats, poultry, seafood, eggs, milk, and cheese. Incomplete proteins — such as those found in beans, grains, nuts, peas, and seeds — lack some essential amino acids and must be eaten in combination for best results.
The functioning of the brain relies on amino acids, as these are the essential components for the
development of neurotransmitters. In turn, neurotransmitters are important factors in brain chemistry, as certain deficiencies or excesses of some neurotransmitters can cause mood disorders. Though amino acids play an essential role in brain function, there are some experts, such as Dr. Andrew Weil (author of Natural Health, Natural Medicine) and Dr. Stuart Berger, who do not believe they should be taken as supplements, as they can severely disrupt the brain chemistry. Some reference texts, such as the Psychotropic Drug Handbook, caution that nondietary amino acid supplements may produce effects different from those found in food. Also, a highly imbalanced intake of amino acids could have an adverse effect on protein synthesis in children.
Amino acids can be in either the "L" or "D" form. The "L" forms are readily absorbed and utilized by the body as proteins, while the "D" forms must be converted by the body into a usable form first; despite the therapeutic value found in some "D" forms, the FDA bans sale of the latter, so you may not encounter it when buying supplements.
Freeform amino acids are ones that have been taken from complex proteins, and you must be sure that, when buying powdered amino acid supplements, the label specifies the amount of free-form amino acids in the product. Chances are that if the label says only "amino acids," the bottle may contain mostly inexpensive protein filler and not much of any amino acids.
Amino acids should be taken with cofactors — such as vitamins, minerals, or nutrients — that assist the body in metabolizing them; it is also a good idea to take a variety of amino acids together and in their proper proportions to one another.
There is one instance, however, where two amino acids play opposite roles and are not compatible with each other: L-tyrosine, which the brain uses to manufacture the neurotransmitters norepinephrine and dopamine —both of which have a stimulating effect, contributing to clear , fast thinking, long-term memory, and alertness — and L-tryptophan, used by the brain to synthesize the neurotransmitter serotonin— which has a sedative effect on the brain, leading to a slower reaction time, a feeling of fullness after a meal, and sleepiness. To get the mental lift from L-tyrosine, it is necessary to eat the proteins (meat, poultry, seafood, beans, tofu, and lentils) in the meal before the food that contains carbohydrates. To relax or fall asleep, it is necessary to eat the foods high in Ltryptophan (bananas, milk, sunflower seeds) first, along with the foods rich in carbohydrates, because they enhance the effect of L-tryptophan. In order to get an energy boost, it is necessary to eat foods high in L-tyrosine. The reason for this is that, even though L-tryptophan needs carbohydrates to get into the brain, it does so much more readily than L-tyrosine.
