What Is Histidine?

Histidine is one of 20 different amino acids. Amino acids are the building blocks of protein and enzymes.

Amino acids are classified as essential or nonessential. Essential amino acids are those that the body cannot make. As a result, they must be obtained in the diet. Nonessential amino acids are those that humans can make from other chemicals in the body; thus, they do not necessarily have to be present in the diet. Histidine is considered an essential amino acid.

Histidine has several functions in the body, including:

• Making proteins
• Forming carnosine (a peptide important for muscle and brain tissue)
• Making histamine (a chemical that mediates allergic reactions)
• Bonding (chelating) of metals
• Helping with the repair and growth of tissue
• Making blood cells
• Protection of nerve cells

This article discusses histidine and its possible uses as a supplement.

Purported Uses of Histidine

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or healthcare provider. No supplement is intended to treat, cure, or prevent disease.

Histidine supplements have been researched for various health conditions. However, there is very little evidence to support the efficacy of histidine supplementation. Most research showing some promising results has been for those with obesity and metabolic syndrome. Histidine also appears to have some appetite-reducing effects.

Obesity and Metabolic Syndrome

A study looked at histidine supplementation in 100 women with obesity and metabolic syndrome and assessed insulin resistance, inflammation, oxidative stress, and metabolic disorders. After 12 weeks, those who took histidine supplements demonstrated:

• Lowered insulin resistance (cells do not respond as they should to insulin)
• Lowered fat mass
• Suppressed inflammation and oxidative stress

A separate systematic review of 30 different studies found that people with obesity who took histidine-containing dipeptides vs. a placebo had lower waist circumferences and decreased fasting glucose and hemoglobin A1c levels. Hemoglobin A1C measures glucose control over the previous three months.

Histidine Deficiency

A histidine deficiency is possible but rare. A histidine-deficient diet doesn't result in a negative nitrogen balance for at least a month (longer than it takes for other essential amino acids). A negative nitrogen balance represents net protein breakdown in the body.

Histidine-deficient individuals have low plasma levels of histidine and may experience atopic dermatitis. They may also have low hemoglobin levels and anemia.

If you have a low protein intake in your diet for a month or more, discuss your diet and supplement concerns with your healthcare provider. Amino acid profiles in the blood can be measured, but this is rarely done. Any suspected single amino acid deficiencies can be corrected with adequate protein intake.

What Are the Side Effects of Histidine?

Histidine is well tolerated and safe when taken at low supplement doses (less than 4.5 grams or 4,500 milligrams per day) in healthy people for a short period (four weeks), according to the 2005 U.S. Dietary Reference Intake Report. If consumed in excess, more side effects may occur. Refer to the section below on what happens if you take too much histidine.

Some have reported lower levels of folic acid, anorexia or reduced appetite, and a greater loss of zinc.

Precautions

Taken in proper doses, histidine is considered safe for most people. However, you should be cautious about histidine supplementation and consult your healthcare provider if the following apply to you:

• You are pregnant or breastfeeding: There is not enough data to prove the safety of histidine supplementation.
• You have folic acid deficiency: Histidine supplements can cause a chemical called formiminoglutamic acid (FIGLU) to build up in the body in those with folic acid deficiency. 
• You have liver disease or liver failure: Histidine supplementation may lead to liver enlargement, high ammonia levels in the blood, and low levels of branched-chain amino acids.

Dosage: How Much Histidine Should I Take?

The Food and Agricultural Organization (FAO) of the UN suggests that histidine requirements for dietary intake are 8 to 12 milligrams (mg) per kilogram (kg) of body weight. The recommended dietary allowance (RDA) for histidine is also 8 to 12 milligrams per kilogram of body weight for adults.

The average adult consumes much more than this requirement through diet alone (30 to 35 milligrams per kilogram).

For supplementation, there is not enough information to recommend a specific dose. In one study, 4 grams of histidine daily for 12 weeks appeared to be safe and without side effects.

What Happens If I Take Too Much Histidine?

There are no reports of histidine toxicity. Also, there is no tolerable upper limit (TUL) established. Yet some healthcare institutions warn against single amino acid supplementation for the following reasons:

• It may lead to a negative nitrogen balance.
• Increased intake of single amino acid supplements may cause an amino acid imbalance.

Single amino acid supplements are not recommended for those with an adequate protein intake in their diet.

People with liver failure could experience complications with histidine supplementation, including liver enlargement and further progression of liver disease.

Taking 8 grams of histidine daily or more has resulted in anorexia and weight loss. Taking higher amounts of histidine (24 to 65 grams daily) may cause:

• Gastrointestinal symptoms
• Headaches
• Drowsiness
• Muscle weakness
• Changes to taste and smell

Interactions

There are no known medication interactions with histidine.

How to Store Histidine

It is best to follow manufacturer directions for proper storage of supplements. As always, store medications and supplements out of the reach of children and pets to prevent accidental consumption.

Similar Supplements

Amino acid supplements are available as single amino acids, combination amino acids (e.g., branched-chain amino acids), or protein supplements. 

Since amino acids combine to form proteins, any protein supplement or powder will also provide histidine. Be sure to read supplement fact labels to know how much histidine you are taking from all sources.

Sources of Histidine & What to Look For

Histidine is found mostly in high-protein foods, including:

• Eggs
• Beef
• Chicken
• Pork
• Fish

Plant-based sources of histidine include:

• Soy
• Beans
• Wheat
• Quinoa
• Corn
• Rice

Single amino acid supplements are available, but histidine can also be found in protein supplements and powders.

When looking for supplements, be sure to look for ones that have been third-party tested. This ensures the quality of the supplement, meaning that it contains what the label claims and is free of contaminants. Supplements with seals from USP, ConsumerLabs, and NSF have been third-party tested.

Summary

Histidine is an essential amino acid. Assuming adequate protein intake, deficiency is rare, and single amino acid supplementation is usually not needed. You will get enough histidine if you consume the right amount of protein.

Histidine supplementation has been marketed for several conditions, but not enough research supports its use. Preliminary research suggests histidine may be helpful for people with metabolic syndrome and obesity, but more research is needed. Therefore, using histidine supplements to self-treat any health condition is not recommended. Always consult your healthcare provider before starting a new supplement.