Tannins are plant polyphenols that can bind to proteins and other compounds. They contribute to an astringent taste and have antioxidant activity.

Which foods and drinks are high in tannins?

Common sources include tea, red wine, cocoa, some berries and grapes, pomegranates, and certain nuts and legumes. Levels vary by plant variety and processing.

Do tannins reduce iron absorption?

Yes, tannins can reduce absorption of non-heme iron (the type found in plant foods) by binding to it in the gut. This effect is strongest when tannin-rich drinks are consumed with meals.

Are tannins good or bad for digestion?

Tannins can have astringent effects that may help with occasional diarrhea. At high intakes, they may irritate the gut in some people or interfere with absorption of certain nutrients.

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Tannins

Mixed study results·5/10

A higher score indicates better study conditions, but not necessarily effectiveness.

Tannins are plant polyphenols found in tea, wine, some fruits, and nuts, known for antioxidant and astringent effects, but may impact nutrient absorption.

Digestion & Gut Health Anti-inflammatory Cardiovascular Support Antioxidant

dose range

0–0 µg

Consumption

—

Not fat-soluble.

Best time

Description

Tannins are a group of polyphenolic compounds widely distributed in plant foods and beverages. While they provide antioxidant, anti-inflammatory, and potential cardiovascular benefits, they can also inhibit the absorption of some nutrients, especially iron.

benefits

Main effects with level of evidence

Mixed

Note on evidence

Tannins are associated with several potential health benefits, especially as antioxidants, but strong human evidence is mainly for their interactions with nutrient absorption rather than specific therapeutic effects.

Antioxidant properties

Moderate

Tannins can neutralize free radicals and protect cells from oxidative damage.

Particularly relevant for: General Population

Examine_Tannins · Examine.com – Tannins PMID_30251946 · PMID: 30251946 – Tannins and Human Health: A Review

May support cardiovascular health

Limited

Some tannin-rich foods may help reduce markers of cardiovascular risk by improving endothelial function and lowering inflammation, though direct effects are still under study.

Particularly relevant for: Adults at risk of cardiovascular disease

PMID_30251946 · PMID: 30251946 – Tannins and Human Health: A Review NIH_Tannins_Factsheet · National Center for Complementary and Integrative Health – Polyphenols and Tannins

May help modulate inflammation

Limited

Tannins have demonstrated anti-inflammatory effects in cell and animal studies; human data is less robust.

Particularly relevant for: General Population

PMID_30251946 · PMID: 30251946 – Tannins and Human Health: A Review Examine_Tannins · Examine.com – Tannins

Potential digestive health effects

Mixed

Tannins have astringent properties and may reduce diarrhea, but can also interfere with nutrient absorption at high intakes.

Particularly relevant for: Individuals with acute diarrhea

EFSA_Tannins_Opinion · European Food Safety Authority – Scientific Opinion on Tannins PMID_30251946 · PMID: 30251946 – Tannins and Human Health: A Review

Safety & Information

Important safety information & known risks

For educational purposes only • not medical advice

Tannins from foods are generally safe for most adults, but high or supplemental intake may lead to gastrointestinal discomfort and interfere with iron absorption.

warning notices

High intake can reduce iron absorption, potentially contributing to anemia in susceptible individuals.
Large amounts may aggravate existing gastrointestinal conditions like ulcers.
Routine dietary intake from foods is not linked to toxicity in healthy adults.
Avoid high intake if you have iron-deficiency anemia, as tannins may inhibit iron absorption.
People with gastrointestinal disorders such as peptic ulcers should use tannins cautiously, as they may exacerbate symptoms.
Use cautiously if taking iron supplements or medications, as tannins may reduce their effectiveness.

Known interactions with medications

May affect the absorption of certain oral medications; space administration apart from high-tannin foods or beverages.

Contraindications / special precautions

Iron-deficiency anemia
Gastrointestinal ulcers

interactions

Important interactions between active ingredient ↔ supplement / medication / food

Tannins can interfere with the absorption of iron and some other nutrients and may interact with certain medications.

Tannins reduce non-heme iron absorption.

nutrient · Iron

SeparateStrongSeparate by 1–2h

Why

Tannins can bind to non-heme iron in plant foods, making it less available for absorption, especially if consumed together.

recommendation

Separate high-tannin foods/beverages from iron supplements and iron-rich meals by at least 1–2 hours.

ODS_Iron_Factsheet · NIH ODS – Iron Fact Sheet for Health Professionals EFSA_Tannins_Opinion · European Food Safety Authority – Scientific Opinion on Tannins NIH_Tannins_Factsheet · National Center for Complementary and Integrative Health – Polyphenols and Tannins

mechanisms of action

Brief explanations of how it works

Free radical scavenging

Tannins can donate electrons to neutralize reactive oxygen species, reducing oxidative stress.

Examine_Tannins · Examine.com – Tannins PMID_30251946 · PMID: 30251946 – Tannins and Human Health: A Review

Inhibition of nutrient absorption

Tannins can bind dietary minerals like iron and protein, reducing their gastrointestinal absorption.

EFSA_Tannins_Opinion · European Food Safety Authority – Scientific Opinion on Tannins ODS_Iron_Factsheet · NIH ODS – Iron Fact Sheet for Health Professionals

Sources & References

Primary literature and reviews on which these statements are based

6 sources

NIH_Tannins_Factsheet

National Center for Complementary and Integrative Health – Polyphenols and Tannins

Examine_Tannins

Examine.com – Tannins

PMID_30251946

PMID: 30251946 – Tannins and Human Health: A Review

EFSA_Tannins_Opinion

European Food Safety Authority – Scientific Opinion on Tannins

ODS_Iron_Factsheet

NIH ODS – Iron Fact Sheet for Health Professionals

Iron interaction overview

Review_Tannin_Absorption

Comprehensive Review: Tannins – Bioavailability and Impact on Health

Last updated: February 7, 2026

This information is for educational purposes only and does not replace medical advice.