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Limited evidenceGeneral health

L-Histidine

An essential amino acid and the precursor of histamine and carnosine. A couple of small trials in specific patient groups showed something; there is no case for supplementing it if you eat protein.

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What the science says

  • Insulin resistance in obese women Limited evidence

    A randomised controlled trial gave 4 g/day of histidine for 12 weeks to 100 obese women with metabolic syndrome and reported reduced HOMA-IR, BMI and inflammatory markers. It is one trial, in one narrow population, from one centre, and has not been replicated.

  • Atopic dermatitis Limited evidence

    An open-label pilot study of oral L-histidine in adults and young children with atopic dermatitis reported improvement in eczema severity, on the theory that histidine feeds filaggrin-derived skin moisturising factor. It was uncontrolled and small, so placebo and regression to the mean cannot be excluded.

Dosage & safety

Studied doseThe metabolic-syndrome trial used 4 g/day in divided doses. Supplement labels typically suggest 500–1000 mg/day. A normal mixed diet supplies roughly 2–3 g/day, well above requirement.
SafetyWell tolerated at gram doses in the short trials available. Because histidine is the substrate for histamine, people with histamine intolerance or mast cell disorders may not tolerate it. Contraindicated in histidinaemia, and unstudied in pregnancy. High single-amino-acid doses can unbalance other amino acids.

How to take it

TimingSplit gram-scale doses across the day; the trials used divided doses rather than one hit.
With food?Take it away from high-protein meals, which supply competing amino acids, if you are aiming for the trial dose.
Worth knowingIf you get flushing, headache or itching after taking it, stop — histidine is the direct precursor of histamine and people with histamine intolerance often react.

Interactions

With other supplements

  • other single amino acids taken in gram doses

    Large doses of one amino acid compete with others for the same intestinal and blood-brain transporters. do not stack several gram-dose amino acids at the same time

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

What is L-histidine good for?

L-histidine is an essential amino acid and the precursor of histamine and carnosine, but the evidence for supplementing it is limited to a couple of small trials in specific patient groups. If you eat protein, there is no case for taking extra L-histidine.

Does L-histidine help insulin resistance?

One trial gave 4 g/day of L-histidine for 12 weeks to 100 obese women with metabolic syndrome and reported lower HOMA-IR and inflammatory markers. It is a single unreplicated trial from one centre, so the evidence is limited.

Does L-histidine help eczema?

Only an uncontrolled open-label pilot study reported improvement in atopic dermatitis with L-histidine, so placebo and regression to the mean cannot be excluded. The evidence is limited.

Can L-histidine cause histamine reactions?

Yes, because L-histidine is the direct precursor of histamine, people with histamine intolerance or mast cell disorders may react. Stop if you get flushing, headache or itching after taking it.

Scientific references

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