Licorice Root
Glycyrrhiza glabra/uralensis · Gān Cǎo 甘草
The 'great harmonizer' — soothing but blood-pressure sensitive.
Evidence tier
Moderate
Research weight
Citations
17 verified / 17
Classification
TCM Herb
❝
What the evidence says. Several controlled trials; effects real but modest or context-dependent.
What is Licorice Root?
Licorice Root (Glycyrrhiza glabra/uralensis · Gān Cǎo 甘草) is a traditional Chinese medicine herb used for indigestion / functional dyspepsia (dgl). NutriDex grades the human evidence as Moderate. Licorice (Gān Cǎo) appears in more TCM formulas than almost any other herb, used to 'harmonize' and soothe. Deglycyrrhizinated licorice (DGL) has reasonable evidence for easing functional dyspepsia and supporting the stomach lining. However, whole licorice contains glycyrrhizin, which in excess raises blood pressure, lowers potassium, and causes fluid retention — a well-documented risk, so DGL or short-term limited use is preferred.
Purported Benefits
✓Indigestion / functional dyspepsia (DGL)
✓Soothes sore throat & ulcers
✓Harmonizes TCM formulas
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
| Outcome | Evidence | Effect | Studies |
|---|---|---|---|
| Functional dyspepsia / indigestion (DGL)One RCT found DGL reduced dyspepsia symptoms vs placebo; limited replication. | Preliminary | ↑ benefit · moderate | 1 |
| Recurrent aphthous stomatitis / mouth ulcers (topical)Two systematic reviews of small trials found topical licorice reduced ulcer pain, size, and healing time. | Moderate | ↑ benefit · moderate | 2 |
| Raised blood pressure (glycyrrhizin pseudohyperaldosteronism)Multiple meta-analyses and case reviews confirm glycyrrhizin raises BP and lowers potassium dose-dependently; flavonoids do not. | Strong | ⚠ risk · moderate | 4 |
| Liver enzymes (ALT/AST) in liver diseaseMeta-analysis of 15 RCTs (n=1,367) found glycyrrhizic acid lowered ALT/AST; offset by the BP/potassium risks of glycyrrhizin. | Moderate | ↑ benefit · small | 1 |
| Menopausal hot flashesOne RCT (n=90) reduced hot flash frequency/severity, but symptoms recurred ~2 weeks after stopping. | Preliminary | ↑ benefit · moderate | 1 |
| Prenatal exposure: child neurodevelopment harmOne prospective cohort linked high maternal glycyrrhizin to lower child IQ and more ADHD problems; observational, single cohort. | Preliminary | ⚠ risk · moderate | 1 |
Dosing & Compounds
Typical Dose
DGL 380–760 mg before meals for digestion; whole-root use should be limited and short-term.
Active Compounds
Safety & Cautions
⚠ Whole licorice raises blood pressure and lowers potassium — avoid in hypertension, heart, or kidney disease and in pregnancy. Prefer DGL; limit duration. Educational only — always check with your doctor or pharmacist before combining Licorice Root with any medicine.
Licorice Root drug interactions
Known or theoretical interactions between Licorice Root and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Licorice Root with any medicine.
Avoid
Blood-pressure drugs
Glycyrrhizin raises blood pressure and opposes antihypertensive therapy.
Glycyrrhetinic acid inhibits 11β-HSD2, causing mineralocorticoid excess with sodium/water retention. NCCIH — Licorice Root
Avoid
Diuretics (thiazide/loop)
With diuretics, licorice can cause dangerous hypokalemia and cardiac arrhythmia.
Both increase renal potassium loss; glycyrrhizin's mineralocorticoid effect adds to diuretic K+ loss. NCCIH — Licorice Root
Avoid
Digoxin
Licorice-induced low potassium sensitizes the heart to digoxin — toxicity/arrhythmia risk.
Potassium loss potentiates digoxin binding to cardiac Na+/K+-ATPase, increasing cardiotoxicity. NCCIH — Licorice Root
Key Studies ★ 17 studies
systematic review and meta-analysis
Zhang 2024
✓ PubMed
Meta-analysis of 8 RCTs (n=541) found glycyrrhizic acid significantly raised systolic and diastolic blood pressure, whereas licorice flavonoids had no significant effect.
systematic review and meta-analysis
Liver function meta-analysis 2024
✓ PubMed
Meta-analysis of 15 RCTs (n=1,367) in primary liver disease found licorice significantly reduced ALT (~15.6 U/L) and AST (~7.4 U/L) vs controls, with purified glycyrrhizic acid most effective.
Meta-analysis
Nutrients 2024
✓ Full text
Meta-analysis of 8 RCTs (541 participants) found glycyrrhizic-acid-containing licorice products significantly raised both systolic and diastolic blood pressure, supporting caution in hypertensive individuals.
Systematic review
Pourmasoumi Iran J Med Sci (Topical Licorice for Aphthous) 2023
✓ Full text
Systematic review of clinical trials concluded topical licorice reduced visual analogue scale pain scores, ulcer size, and healing time in recurrent aphthous stomatitis compared with control therapies.
Meta-analysis
Penninkilampi et al. (2017)
✓ PubMed
Systematic review/meta-analysis of 18 studies (n=337) of chronic glycyrrhizic-acid-containing licorice. Significant rise in systolic BP (+5.45 mmHg, 95% CI 3.51-7.39) and diastolic BP (+3.19 mmHg, 95% CI 0.10-6.29), with significant falls in plasma potassium, renin activity and aldosterone (pseudohyperaldosteronism). Dose-BP correlation (SBP r=0.55, DBP r=0.65) even at modest doses.
randomized controlled trial
COVID-19 RCT 2023
✓ PubMed
RCT in 60 moderately ill COVID-19 patients found licorice safe but with no significant benefit on oxygenation, temperature, or respiratory rate, only minor improvements in CRP and ALT.
rct
Compound glycyrrhizin eczema RCT 2020
✓ Full text
Multicenter double-blind RCT (n=193) found oral compound glycyrrhizin added to topical corticosteroid improved chronic eczema: higher EASI-75 response (47.9% vs 21.2%, P<0.001) and lower recurrence (3.2% vs 12.1%, P=0.021) vs placebo.
RCT
Nahidi et al. (2012)
✓ PubMed
Double-blind randomized placebo-controlled trial of licorice root (330 mg x3 daily, 8 weeks) in 90 menopausal women. Frequency and severity of hot flashes decreased significantly versus placebo, with the benefit persisting up to 2 weeks after stopping; symptoms recurred ~2 weeks after therapy ended.
RCT
Tominaga et al. (2009)
✓ PubMed
8-week randomized double-blind placebo-controlled dose-ranging trial of licorice flavonoid oil (0/300/600/900 mg/day) in 84 overweight adults. Total body fat (DXA) decreased significantly in all three LFO groups; the 900 mg/day dose also significantly reduced visceral fat area (CT), body weight, BMI and LDL-cholesterol from baseline, without significant adverse effects.
narrative review
Ceccuzzi 2023
✓ PubMed
Narrative review of 104 case reports confirming that excess liquorice intake causes pseudo-hyperaldosteronism with hypertension and hypokalemia, occasionally progressing to life-threatening arrhythmias, rhabdomyolysis, or coma.
systematic_review
Sadeghi 2023
✓ PubMed
Systematic review of 6 clinical trials (314 subjects) found topical licorice (1-5% paste, patch, or mouthwash) significantly reduced recurrent aphthous stomatitis pain, ulcer size, and healing time (recovery within 4-8 days) with no adverse effects.
Safety / toxicology
Safety literature
✓ Source
Glycyrrhizin excess causes hypertension and hypokalemia (pseudoaldosteronism).
case series
Pseudohyperaldosteronism case series 2024
✓ Full text
Case series of 3 patients with licorice-induced pseudohyperaldosteronism (hypertension and hypokalemia) that resolved after licorice withdrawal, sometimes requiring mineralocorticoid receptor blockers and potassium.
cohort_study
Räikkönen 2017
✓ PubMed
Prospective Finnish birth-cohort study (n=378, mean age 12.5y) in the American Journal of Epidemiology found children of mothers with high prenatal glycyrrhizin intake (>=500 mg/week) scored ~7 IQ points lower, had poorer memory, ~3.3-fold higher odds of ADHD problems, and girls showed accelerated puberty.
authoritative_body
NCCIH 2024
✓ Source
NIH's NCCIH states glycyrrhizin in licorice can cause irregular heartbeat and cardiac arrest with large or long-term use, that ~250 g/week during pregnancy raises preterm-birth risk, and that licorice can interact harmfully with corticosteroids and other medications.
Study
Raveendra 2012
✓ PubMed
DGL extract reduced functional-dyspepsia symptoms vs placebo.
Study
Ulcer studies
✓ Source
DGL supports gastric mucosal protection.