Garlic for Upper Respiratory Tract Infections

A 12-week randomized controlled trial found the garlic group experienced 63% fewer colds, 70% shorter symptom duration, and significantly fewer viral-challenged days (111 vs 365) compared to placebo. While promising, human clinical trials remain limited.

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The Bottom Line

Key Study Findings

Other n=80 3 weeks Double-blind

Investigation of the natural supplement IQP-AS-119 for the prevention of upper respiratory tract infections in …

Dose: 20.0% vs: placebo Outcome: None Effect: or 14 P=0.038

Population: None

Other 17.3 weeks

Protective Effects of AGE and Its Components on Neuroinflammation and Neurodegeneration.

Dose: None vs: None Outcome: None Effect: None None

Population: Alzheimer's disease patients

Review

Treatment of the common cold in children and adults.

Dose: None vs: None Outcome: infection rate Effect: None None

Population: None

Review

Chemoprevention of bladder cancer.

Dose: Various nutrients (selenium, vitamins, green tea) vs: None Outcome: Bladder cancer chemoprevention Effect: None None

Population: Bladder cancer patients

Meta-Analysis

Unsafe and potentially safe herbal therapies.

Dose: None vs: None Outcome: lipid levels Effect: None None

Population: hypertensive patients

Key Statistics

Studies

300

Participants

↑

Positive

Grade

Referenced Papers

Investigation of the natural supplement IQP-AS-119 for the prevention of upper respiratory tract infections in marathon race participants: A randomized, … Other

Experimental and therapeutic … 2021

Protective Effects of AGE and Its Components on Neuroinflammation and Neurodegeneration. Other

Neuromolecular medicine 2016

Treatment of the common cold in children and adults. Review

American family physician 2012

Chemoprevention of bladder cancer. Review

The Urologic clinics … 2002 20 citations

Unsafe and potentially safe herbal therapies. Meta-Analysis

American journal of … 1999 226 citations

Dosage & Usage

mg = milligrams · mcg = micrograms (1,000× smaller) · IU = International Units

Commonly Used Dosages

fresh:: 2-5 g raw garlic/day
general:: 600-1,200 mg aged garlic extract/day

Upper limit: No established UL; high doses may increase bleeding risk

Dosages Studied in Research

Dosage	Duration	Effect	N
20.0%	3 weeks	Mixed	80
None	17.3 weeks	Positive	--
None	--	Mixed	--
Various nutrients (selenium, vitamins, green tea)	--	Positive	--
None	--	Mixed	--

Best taken: With meals to reduce GI discomfort

Safety & Side Effects

Reported Side Effects

⚠ Gastrointestinal discomfort (heartburn, gas, nausea)
⚠ Body and breath odor
⚠ Increased bleeding risk
⚠ Allergic reactions (contact dermatitis, rare)

Known Interactions

● Anticoagulants and antiplatelet drugs (may increase bleeding risk)
● HIV protease inhibitors (saquinavir — may reduce drug levels)
● CYP2E1 substrates (garlic may alter metabolism)
● Isoniazid (may reduce drug absorption)

Tolerable upper intake: No established UL; high doses may increase bleeding risk

Always consult your healthcare provider before starting any supplement.

Frequently Asked Questions

Does Garlic help with Upper Respiratory Tract Infections?

Based on 3 studies with 300 participants, there is moderate evidence from clinical studies that Garlic may support Upper Respiratory Tract Infections management. Our evidence grade is B (Good Evidence).

How much Garlic should I take for Upper Respiratory Tract Infections?

Studies have used various dosages. A commonly studied range is 2-5 g raw garlic/day. Always consult your healthcare provider before starting any supplement regimen.

Are there side effects of Garlic?

Reported side effects may include Gastrointestinal discomfort (heartburn, gas, nausea), Body and breath odor, Increased bleeding risk, Allergic reactions (contact dermatitis, rare). Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.

How strong is the evidence for Garlic and Upper Respiratory Tract Infections?

We rate the evidence as Grade B (Good Evidence). This rating is based on 3 peer-reviewed studies with 300 total participants. The overall direction of effect is positive.

Related Evidence

Other ingredients for Upper Respiratory Tract Infections

Vitamin D A Zinc A Beta-Glucan A Vitamin C B Echinacea B Andrographis B

Quick Verdict

Evidence Strength72%

High confidence

Study Breakdown

RCT (0)Meta (1)Other (2)

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FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.