Last verified: 17 days ago
L-Histidine
Also known as: histidine, His, L-His, histidine monohydrochloride
Evidence under review. — Not yet rated
Amino acid with early evidence for reducing mental fatigue in high-fatigue individuals. Research is limited.
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What it does
L-Histidine is an essential amino acid found naturally in protein-rich foods and used as a building block for proteins, enzymes, and neurotransmitters like histamine. One randomized controlled...
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Evidence quality
Evidence base hasn't been formally rated yet. See research below.
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Clinical dose
No established dose from provided studies
What the Science Says
L-Histidine is an essential amino acid found naturally in protein-rich foods and used as a building block for proteins, enzymes, and neurotransmitters like histamine. One randomized controlled trial found that a single dose may reduce fatigue, confusion, and low mood in people who already experience high levels of fatigue, while also improving vigor after a mental workload. It also appears as a component of carnosine (beta-alanyl-L-histidine), a dipeptide studied for exercise performance and heart health, though those benefits are attributed to carnosine as a whole rather than L-histidine alone.
What It Doesn't Do
Not proven to reduce fatigue in people with normal fatigue levels — the single-dose study only showed effects in a high-fatigue subgroup. Not a proven cognitive enhancer for the general population. No direct evidence it builds muscle or boosts athletic performance on its own. Don't confuse carnosine benefits with L-histidine benefits — they are not the same thing.
Evidence-Based Benefits
May reduce fatigue, confusion, and low mood after mental workload in people with high baseline fatigue.
Weak EvidenceEffective at: No established dose from provided studies
Supporting studies (click to view on PubMed):
As part of carnosine, linked to improved exercise performance and quality of life in heart failure patients.
Weak EvidenceEffective at: 500 mg carnosine daily (from heart failure study)
Supporting studies (click to view on PubMed):
Absorption & Bioavailability
Unknown from provided studies — no pharmacokinetic data reported in the provided papers
Red Flags to Watch For
- The only direct human RCT on L-histidine for fatigue was a single-dose study with significant effects only in a subgroup — not the full study population
- Most papers in this dataset use L-histidine as a chemical tool (nanomaterials, drug delivery) rather than as a dietary supplement — do not confuse lab chemistry uses with human health benefits
- Carnosine-based benefits (exercise, heart failure) are often marketed as L-histidine benefits, but the research was done on the dipeptide carnosine, not isolated L-histidine
- EFSA safety opinion covers L-histidine as an animal feed additive — this does not directly validate human supplement safety or dosing
Products Containing L-Histidine
See how L-Histidine is used in these analyzed products:
Elm & Rye Vegan Protein Blend
Supplement
Thorne Amino Complex Berry Powder NSF
Supplement
Double Wood Supplements Essential Amino Acids
Supplement
Optimum Nutrition 100% Gold Standard Whey
Supplement
Swolverine INTRA
Supplement
Everyday Dose
Supplement
Frequently Asked Questions
What does L-Histidine do?
Amino acid with early evidence for reducing mental fatigue in high-fatigue individuals. Research is limited.
What is the effective dose of L-Histidine?
No established dose from provided studies
Is L-Histidine safe?
The only direct human RCT on L-histidine for fatigue was a single-dose study with significant effects only in a subgroup — not the full study population
What doesn't L-Histidine do?
Not proven to reduce fatigue in people with normal fatigue levels — the single-dose study only showed effects in a high-fatigue subgroup.
Research Sources
- PubMed
- NIH DSLD
This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-05-25