Histidine is considered a "semi-essential" amino acid; adults generally manufacture sufficient amounts of histidine, but children may require supplements at some time. It is also a precursor of histamine, a compound released by the immune system when a person has an allergic reaction.

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.

Anecdotal research suggests that low histidine levels are present in people with rheumatoid arthritis. As such, it has been suggested that histidine supplements can improve arthritis symptoms in some people.

How much histidine should I take?

Because histidine is produced naturally in the body, the recommended daily allowance is unknown. Most studies of histidine have used between 1 and 8 grams per day. Other practitioners recommend taking histidine supplements at the ratio of 8-10 milligrams per day per kilogram of body weight.

What forms of histidine are available?

Histidine is found in a variety of foods, including beef, chicken, and most dairy products, and wheat and rye breads. Histidine supplements are also available, usually in tablet or powder form.

What can happen if I take too much histidine? Are there any interactions I should be aware of? What precautions should I take?

Patients with diseases of the liver or kidneys should not take large amounts of amino acids such as histidine without first consulting with a licensed health care provider. Patients diagnosed with manic depression or bipolar disorder also should not take histidine without the approval of a licensed health care provider. As of this writing, however, no side-effects have been reported among people taking normal doses of histidine supplements. As always, make sure to consult with a licensed health care provider before taking histidine supplements or any other dietary supplement or herbal remedy.