What is L-Histidine?
Histidine is one of the 20 most common natural amino acids. Histidine is present in many proteins. L-histidine cannot be formed by other nutrients, and must be in the diet to be available to the body. Histidine is called a semi-essential amino acid (protein building block) because adults generally produce adequate amounts but children may not.
Histidine is the direct precursor of histamine, it is also an important source of carbon atoms in the synthesis of purines. The side chain of histamine acts as a general acid and base as it participates in the catalytic functions of chymotrypsin, as well as those of a number of enzymes dealing with the metabolism of carbohydrates, proteins, and nucleic acids.
Histidine is mainly found in meat and dairy products. Histidine is not required in the diet but may be required in increased amounts during periods of rapid growth.
Histidine functions, uses, and health benefits:
The body uses histidine to manufacture histamine, and histamine is responsible for a wide range of physiological processes.
Histidine is needed to help grow and repair body tissues, and to maintain the myelin sheaths that protect nerve cells. It also helps manufacture red and white blood cells, and helps to protect the body from heavy metal toxicity. The stomach uses histidine to produce gastric juices.
L-histidine may be indicated for use in some with rheumatoid arthritis. Rheumatoid arthritis is known to be associated with low blood levels of histidine and elevated 3-methylhistidine. Histidine plays a significant role in the growth and repair of tissues, ulcers, hyperacidity, digestion, and gastric juices, as well as in the production of red and white blood cells.
Histamine stimulates the secretion of the digestive enzyme gastrin. Without adequate histamine production healthy digestion can become impaired. Histidine is known to be vital in the maintenance of the myelin sheaths surrounding nerves, particularly the auditory nerve and is used to treat some forms of hearing disability.
Histidine also acts to lower blood pressure and relax blood vessels, and is used to treat various cardiac and circulatory problems. Histidine is an essential component of zinc binding proteins and has an important role in the absorption and transport of zinc. Histidine in conjunction with zinc can increase zinc absorption from the gut.
In its role as a zinc binding protein, histidine is important for the formation of myelin, a type of insulating fat which surrounds many nerve fibres. In a histidine proton shuttle, histidine is used to quickly shuttle protons, it can do this by abstracting a proton with its basic nitrogen to make a positively charged intermediate and then use another molecule, a buffer, to extract the proton from its acidic nitrogen.
In carbonic anhydrases, a histidine proton shuttle is utilized to rapidly shuttle protons away from a zinc-bound water molecule to quickly regenerate the active form of the enzyme.
Dietary sources of histidine:
Histidine can be obtained in a variety of foods, including beans, brewer's yeast, brown rice bran, caseinate, dairy products, eggs, fish, lactalbumin, legumes, meat, nuts, seafood, seeds, soy, whey, whole grains. Dairy, meat and poultry, and fish are good sources of histidine.
Histidine dosage, intake:
Most people do not need to supplement histidine. Most studies of histidine have used between 1 and 8 grams per day.
According to limited research, many people with rheumatoid arthritis have low levels of histidine. Histidine deficiency in babies causes eczema. Histidine deficiency can result in cataracts (diets that exclude Histidine result in Cataracts within three weeks). Histidine deficiency is suspected to be associated with stomach and duodenal ulcer.
Toxicity, side effects, interactions, and contraindications:
There are no known signs of toxicity from histidine. Large doses of histidine can cause premature ejaculation, reduces levels of zinc and possibly trigger an allergic or asthmatic reaction (due to increases in histamine). Long-term supplementation with Histidine may give rise to a copper deficiency and raise blood cholesterol levels. L-histidine is generally well tolerated.
Douglas Lab's L-Histidine
FTH's Amino Health