Ken Ward's Health and Nutrition Pages
Essential Amino Acids
|To understand proteins better, you need to know
about amino acids. Although there are more than 300 amino acids used in the body, only 8
of these are essential in the diet of adults. One amino acid, histidine, is essential in
the diet of infants and children.
Proteins are made up of essential amino acids. The word essential means that these amino acids (compared with other amino acids) cannot be made by the body, but must be obtained from the diet. It also means that without these amino acids normal health and wellbeing are not possible. The other amino acids can be made in the body of adults from the basic eight:
Branched-chain Amino Acids (BCAA)
Chemically, branched-chain amino acids have side chains.
Sulphur Amino Acids
Free-form Essential Amino Acids
Description of Essential Amino Acids
Branched-chain Amino Acids
Branched-chain amino acids constitute approximately 70 percent of the amino acids in the body proteins. That is, they are especially important in building body organs. Wound healing is enhanced with supplements of all three branched chain amino acids - valine, leucine and isoleucine - and they may be helpful in stress.
In injury and stress, the branched-chain amino acids in muscles, and in organs of the body, may be broken down by the liver to produce glucose. This may also occur in certain diets. Because the body has a great need for energy, after using up the glycogen resources in the liver, it turns first to the muscles for an energy source (and even to vital organs if the stress is prolonged).
Their breakdown produces raw materials for making fatty acids, which are used to make phospholipids. Phospholipids are the building blocks of cellular membranes - which are part of every bodily tissue and organ - especially the brain.
Low levels of these amino acids are found in the blood of those suffering with liver disease.
Valine is involved in the detoxification of ammonia, and may help to prevent muscle wasting in diabetes and ammonia-toxicity in hospitalized old people.
Leucine may prevent protein wasting in injury, stress and starvation. It also helps the body to utilize insulin and may be useful in adult-onset diabetes.
Isoleucine has the properties of the branched chain amino acids.
Sulphur Amino Acids
Methionine is essential for the production of taurine - an amino acid that is important for heart function and nerve transmission. Deficiency of methionine interferes with the production of phospholipids that are important for the nervous system and for preventing blood stickiness.
Methionine, cysteine, and cystine are all sulphur containing amino acids. Methionine can break down fats and is a powerful antioxidant and also protects the body from toxic substances. Combined with folic acid choline, it protects against some cancers.
It has been used to treat paracetamol overdose, and to remove heavy metals from the body.
Methionine composes 25% of collagen - necessary to give structure to the skin.
Legumes are short of methionine, so vegetarians get their mehtionine from cereals. Beens, beef, milk, and eggs have sufficient mehtionine.
Free-form Essential Amino Acids
Tryptophan is a precursor of the neurotransmitter serotonin. - a compound that occurs in the brain, intestines, and blood platelets and acts as a neurotransmitter, as well as inducing vasoconstriction and contraction of smooth muscle. Serotonin is also known as 5-hydroxytryptamine. It is believed to play an important role in mood. Some antidepressants prevent the nerves from taking in serotonin and therefore increase the amount of serotonin in the brain.
Tryptophan has been used in the treatment of depression, especially dpression associated with insomnia. Tryptophan can cause sleepiness, and this may be present the day after. Tryptophan is a precursor of the pineal hormone melatonin, which is associated with sleep.
Tryptophan appears to reduce the pain of arthritis. Both pregnant people and those with jaundice have high levels of tryptophan in the blood and both groups experience a relief from arthritis.
Oestrogen contraceptives interfere with the conversion of tryptophan into serotonin. This may be due to the effects of the pill on B6.
Tryptophan is converted in the body to niacin (vitamin B3) and picolinic acid. Giving high doses of vitamin B6 along with tryptophan increases its conversion to niacin and decreases its uptake into the nervous system.
When used as a supplement, tryptophan should be taken with some carbohydrate, such as fruit juice, because the insulin secreted in response to the carbohydrate helps the absorption of tryptophan. It should not be taken with other amino acids, as these interfere with its absorption. It should be taken between meals.
Maize is limited in terms of tryptophan.
Lysine is required by the body to make carnitine - an amino acid used to metabolize fats. Lysine is required in collagen and elastin (the major proteins of the body). This dependent upon the enzyme lysloxidase, which requires copper - deficiency of which can cause imperfections in collagen or elastin. This may be important in the aging process.
Lysine deficiency can interfere with carnitine synthesis and have adverse impact upon fat metabolism to energy. Wheat, rice, maize and millet are deficient in lysine, however, it can be supplied by beans, milk, eggs, animal meat and fish
Used for recurrent colds and herpes infections.
Phenyalanine is a precursor of adrenalin and noradrenalin (catecholamines), which are neurotransmitters. Suppementation with phenylalanine has normalized both high and low blood pressure. With the non-essential amino acid tyrosine, it has been helpful with some types of depression.
Whereas tryptophan induces sleepiness, phenyalanine has the opposite effect and, because it produces adrenalin should not be given to anxious people.
Some individuals cannot digest phenylalanine, and have a condition called phenylketonuria. The amino acid tyrocine can be made only from phenylalanine, so sufferers from phenylketonuria may require supplements of tyrosine (which for them is an essential amino acid).
Threonine can be converted into glucose by the liver. It is important when an individual suffers stress or injury, and may be supplemented under those conditions. It is therefore similar in this respect to the branched-chain amino acids valine, isoleucine, and leucine, which are also used to provide the energy needed to handle stress and injury.
The process whereby energy is created from non-carbohydrate sources (when these have been used up) is called gluconeogenesis. Glucogenesis occurs in the liver and kidneys, and converts amino acids into glucose. Threonine, along with valine, isoleucine and leucine are amino acids that are more readily used in clucogenesis.
Other Amino Acids
Histidine is not essential in adults, because it is manufactured in the liver from other amino acids. It is an essential amino acid in infants and children.
Histidine produces histamine, which is involved in the inflammatory response and the production of hydrochloric acid by the stomach.
Some reports have shown improvement of arthritis with histidine supplementation. Histidine is associated with histamine, which means people with allergies could suffer more if they take histidine. Histidine deficiency in babies causes eczema.