Gallic Acid

PhytochemicalPhenolic acidBest with a meal

What is it

Gallic acid (3,4,5-trihydroxybenzoic acid) is a naturally occurring phenolic compound found widely in plants including gallnuts, sumac, tea, grapes, and many fruits. It is the basic building block of hydrolyzable tannins and is widely used as a chemical reference standard and antioxidant marker in supplements.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Antioxidant activity (marker compound)

Limited Evidence

Gallic acid is a potent antioxidant in vitro and contributes to the antioxidant activity of many polyphenol-rich plant extracts. Direct clinical evidence for isolated gallic acid is limited; most benefit comes from whole polyphenol intake.

Anti-inflammatory activity

Mixed Evidence

Preclinical studies show gallic acid downregulates NF-kB and other inflammatory pathways in cells and animal models. Human evidence is limited to broader polyphenol intervention studies.

How it works

Gallic acid is a small polyphenol with three adjacent hydroxyl groups on a benzene ring, giving it strong electron-donating and metal-chelating properties. It functions as an antioxidant by scavenging free radicals and as a metal chelator binding iron and other transition metals. In supplements, gallic acid is most often present as a constituent of plant extracts containing tannins (gallotannins, ellagitannins). On its own, gallic acid is absorbed in the small intestine and rapidly metabolized to methylated, sulfated, and glucuronidated forms, with peak plasma concentrations within 1 to 2 hours. The bioavailability of free gallic acid is moderate; when consumed as part of complex tannins, slower release in the gut can extend exposure. Gallic acid is also widely used as a reference marker for total polyphenol content, expressed as gallic acid equivalents (GAE). Preclinical studies suggest antioxidant, anti-inflammatory, antimicrobial, and antitumor activities in cell culture and animal models. Direct human clinical evidence for isolated gallic acid supplementation is limited.

Dosage

There is no RDA. Most exposure comes from polyphenol-rich foods and plant extracts rather than isolated supplements. Standardized polyphenol extracts may list gallic acid equivalents in the milligrams to hundreds of milligrams per serving range. Isolated gallic acid supplements are uncommon; experimental doses in research have varied widely.

When and how to take it

Gallic acid in supplements is typically taken with meals. To minimize mineral binding effects, separate gallic acid-rich extracts from iron, zinc, or calcium supplements by at least 2 hours. No clear timing preference for antioxidant effects.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Free gallic acid

Pure gallic acid used as a reference standard and rarely as a stand-alone supplement.

Moderately absorbed; rapid metabolism.

Hydrolyzable tannins (gallotannins, ellagitannins)

Found in pomegranate, grape, and oak-derived extracts. Released gallic acid contributes to systemic exposure.

Slower release as tannins are hydrolyzed in the gut.

Safety

Considered safe at typical dietary and supplement levels. At very high concentrations, gallic acid can be a pro-oxidant in vitro and may cause GI upset in some users. Allergic reactions are rare. No formal Tolerable Upper Intake Level has been established.

Who should be cautious

People with iron-deficiency anemia should separate tannin-rich supplements from iron supplements or meals high in iron by at least 2 hours. Pregnant and breastfeeding women should rely on food sources rather than concentrated supplements due to limited safety data.

Interactions

Gallic acid and tannins can bind to iron and other minerals in the gut, reducing their absorption when taken at the same time. Theoretical interactions with anticoagulants (mild antiplatelet activity in preclinical data) exist but are not clinically documented.

Food sources

Black tea

Amount
1 cup
%DV
—

Pomegranate

Amount
1 medium
%DV
—

Sumac

Amount
1 teaspoon
%DV
—

Berries (raspberries, blackberries)

Amount
1 cup
%DV
—

Grapes

Amount
1 cup
%DV
—

Walnuts

Amount
1 oz
%DV
—

Frequently asked questions

What does GAE (gallic acid equivalents) mean on a label?⌄

It is a standardized way to report total polyphenol content using gallic acid as the reference. A higher GAE generally indicates more polyphenol content, though the specific polyphenol composition matters.

Is gallic acid safe to take?⌄

At dietary and typical supplement levels, yes. Very high doses or pure gallic acid have not been well studied in humans, and tannin-rich extracts can interfere with mineral absorption.

Should I look for gallic acid in supplements?⌄

It is more useful as a marker of polyphenol content in plant extracts than as a stand-alone supplement. Whole-food polyphenol sources offer a broader range of bioactive compounds.

References

Gallic Acid on Wikidata — Wikidata link

Gallic Acid (ChEBI:73731) — ChEBI link

Gallic Acid (PubChem CID 6439848) — PubChem link

Gallic Acid on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Gallic Acid (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.