The Eight Essential Amino Acids (*). Essential only in certain cases
1 Isoleucine Deficiency of isoleucine is only found in people deficient in dietary protein but symptoms may include headaches, dizziness, fatigue, depression, confusion as well as irritability. Symptoms of deficiency may mimic the symptoms of hypoglycemia. This nutrient has also been found to be deficient in people with mental and physical disorders, but more research is required on this.
As a food additive Isoleucine has E number E641 and is classified as a flavour enhancer.
2 Leucine Leucine helps with the regulation of blood-sugar levels, the growth and repair of muscle tissue (such as bones, skin and muscles), growth hormone production, wound healing, as well as energy regulation. It can assist to prevent the breakdown of muscle proteins that sometimes occur after trauma or severe stress. It may also be beneficial for individuals with phenylketonuria - a condition in which the body cannot metabolize the amino acid phenylalanine.
A Deficiency of this nutrient is rare, since all protein foods contains it, but vegans and vegetarians without adequate protein sources may suffer from a deficiency. Hypoglycemia symptoms may appear if the diet is deficient and may include dizziness, fatigue, headaches, irritability etc.
As a food additive L-Leucine has E number E641 and is classified as a flavour enhancer.
3 Lysine The human nutritional requirement is 1–1.5 g daily. It is the limiting amino acid (the essential amino acid found in the smallest quantity in the particular foodstuff) in all cereal grains, but is plentiful in all pulses (legumes). Plants that contain significant amounts of lysine include:[citation needed]
1. Buffalo Gourd (10,130–33,000 ppm) in seed
2. Berro, Watercress (1,340–26,800 ppm) in herb.
3. Soybean (24,290–26,560 ppm) in seed.
4. Carob, Locust Bean, St.John's-Bread (26,320 ppm) in seed;
5. Common Bean (Black Bean, Dwarf Bean, Field Bean, Flageolet Bean, French Bean, Garden Bean, Green Bean, Haricot, Haricot Bean, Haricot Vert, Kidney Bean, Navy Bean, Pop Bean, Popping Bean, Snap Bean, String Bean, Wax Bean) (2,390–25,700 ppm) in sprout seedling;
6. Bean Nut, Benzolive Tree, Jacinto (Sp.), Moringa (aka Drumstick Tree, Horseradish Tree, Ben Oil Tree), West Indian Ben (5,370–25,165 ppm) in shoot.
7. Lentil (7,120–23,735 ppm) in sprout seedling.
8. Asparagus Pea, Winged Bean (aka Goa Bean) (21,360–23,304 ppm) in seed.
9. Fat Hen (3,540–22,550 ppm) in seed.
10. Lentil (19,570–22,035 ppm) in seed.
11. White Lupin (19,330–21,585 ppm) in seed.
12. Black Caraway, Black Cumin, Fennel-Flower, Nutmeg-Flower, Roman Coriander (16,200–20,700 ppm) in seed.
13. Spinach (1,740–20,664 ppm).
14. Quinoa
15. Kasha
16. Amaranth, (Wonder Oil ) A close relative of pigweed, amaranth has been valued since ancient times for its nutritional and ornamental qualities. One of the highest-protein grains, with numerous medicinal attributes, amaranth has excellent potential in health food and nutraceutical markets. Amaranth's sweet, nutty flavor complements a range of cereal products, and its starch could replace fat in processed foods. The genus Amaranthus includes about sixty species which are classified according to their uses as grain amaranths, leaf amaranths (A. tricolor), and dual-purpose amaranths. Chinese spinach or yin choy (var.gangeticus), A. dubius, A. hybridus, and A. cruentus all belong to the very useful leaf amaranths of the Third World.
Amaranth is high in protein, lysine, calcium, iron and fiber - all useful as functional ingredients in cereal products. Amaranth oils are high in "squalene", a powerful antioxidant used as a dietary supplement for diabetics and those suffering from hypertension and metabolic disorders.
There is another substance Amaranth derived from Coal Tar with the same name that was used in food & make-up as Red coloring but is now Forbidden in some countries as additive E123
Good sources of lysine are foods rich in protein including meat (specifically red meat, pork, and poultry), cheese (particularly Parmesan), certain fish (such as cod and sardines), and eggs.
4 Methionine High levels of methionine can be found in sesame seeds, Brazil nuts, fish, meats, and some other plant seeds. Most fruits and vegetables contain very little of it; however, some have significant amounts, such as spinach, potatoes, and boiled corn. Most legumes, though high in protein, are also low in methionine. DL-methionine is sometimes added as an ingredient to pet foods.
5 Phenylalanine
Found naturally in the breast milk and manufactured for food and drink products and are also sold as nutritional supplements for its reputed analgesic and antidepressant effects. Phenylalanine is structurally closely related to dopamine,(neurotransmitter) epinepherine (adrenaline) and tyrosine. High amounts can affect serotonin levels Serotonin is also found in many mushrooms and plants, including fruits and vegetables. Too much Phenylalanine can have an adverse effect on Serotonin functioning
6 Threonine Other nutrients are better absorbed when threonine is present, deficiency may result in irritability and a generally difficult personality. It has also been used as part treatment of mental health conditions
Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, and sesame seeds.
7 Tryptophan For some time, tryptophan has been available in health food stores as a dietary supplement, although it is common in dietary protein. Many people found tryptophan to be a safe and reasonably effective sleep aid, probably due to its ability to increase brain levels of serotonin (a calming neurotransmitter when present in moderate levels
In the central nervous system, serotonin plays an important role as a neurotransmitter in the modulation of anger, aggression, body temperature, mood, sleep, sexuality, appetite, and metabolism, as well as stimulating vomiting.

Serotonin has broad activities in the brain, and genetic variation in serotonin receptors and the serotonin transporter, which facilitates reuptake of serotonin into presynapses, have been implicated in neurological diseases. Drugs targeting serotonin-induced pathways are being used in the treatment of many psychiatric disorders, and one focus of clinical research is the influence of genetics on serotonin action and metabolism in psychiatric settings. Such studies have revealed that the variation in the promoter region of the serotonin transporter protein accounts for nearly 10% of total variance in anxiety-related personality,[2] and the effect of this gene on depression was found to interact with the environment.[3] conditions typically associated with low serotonin levels or activity in the brain such as premenstrual dysphoric disorder and seasonal affective disorder. In particular, tryptophan has been showing considerable promise as an antidepressant alone
8 Valine It has a stimulating effect and is needed for muscle metabolism, repair and growth of tissue and maintaining the nitrogen balance in the body.
Since it is a branched-chain amino acid, it can be used as an energy source in the muscles, and in doing so preserves the use of glucose.
Many amino acids become deficient with drug addiction, and here it also plays an important role and there are indications that it may also be beneficial in treating alcohol related brain damage, as well as degenerative neurological conditions.
A deficiency may affect the myelin covering of the nerves.