Exploring What High Tannins Do: Effects, Benefits, and Side Effects

January 5, 2026 •

4 min read

Tannins are a group of naturally occurring chemical compounds, also known as polyphenols, found in many plant-based foods and drinks like wine and tea. But what do high tannins do to your body and your sensory experience? They are responsible for the distinctive astringent and bitter sensations in many of our favorite foods and beverages.

Quick Summary

An overview of the roles high tannins play in the flavor and texture of various foods and drinks, from wine to tea. Covers potential health benefits and important negative side effects.

Key Points

Astringent and Drying Sensation: High tannins bind to proteins in saliva, causing a drying, bitter, and puckering sensation in the mouth.
Impact on Wine Flavor: In red wine, tannins add structure, body, and complexity, and help in the aging process, softening over time.
Health Benefits as Antioxidants: Tannins act as powerful antioxidants with anti-inflammatory and cardioprotective effects, potentially reducing the risk of chronic diseases.
Interference with Iron Absorption: A notable side effect is their ability to inhibit the absorption of non-heme iron from plant-based foods, especially when consumed together.
Contribute to Nausea: Some individuals with sensitive digestive systems may experience stomach irritation and nausea from high tannin intake, particularly on an empty stomach.
Food and Drink Sources: Common high-tannin sources include red wine, black tea, dark chocolate, walnuts, and unripe fruits.

What Are Tannins?

At a basic level, tannins are phenolic compounds produced by plants, serving as a defense mechanism against insects and animals. They are present in the skins, seeds, and stems of grapes, coffee beans, tea leaves, and certain nuts and fruits. The term "tannin" originates from the Old German word for oak bark, reflecting its historical use in tanning animal hides. Structurally, tannins are known for binding and precipitating proteins, which creates a drying sensation in the mouth. Tannins are broadly classified into hydrolyzable and condensed types, found in various sources and possessing different effects.

High Tannins in Food and Drink: A Sensory Experience

The most recognizable effect of high tannins is the astringent, drying, and slightly bitter sensation they impart on the palate, particularly noticeable in red wine and black tea.

High Tannins in Wine

In red wine, tannins primarily derive from grape skins, seeds, and stems during fermentation. The duration of contact with these components influences the tannin level. Wines high in tannins, like Cabernet Sauvignon or Nebbiolo, are often full-bodied and may feel coarse when young. With aging, tannins polymerize, leading to a smoother texture and a more intricate flavor profile. They also function as natural antioxidants, aiding in graceful aging. The astringency of tannins makes high-tannin wines a good match for rich, fatty foods like red meat, as they bind to proteins and cleanse the palate.

High Tannins in Tea

High tannin content in tea, especially black tea, contributes to its briskness and color. Factors such as tea type and steeping time can affect concentration. Excessive steeping can release too many tannins, resulting in a bitter taste. Interestingly, polyphenol breakdown during black tea oxidation may reduce astringency compared to green tea. Tea tannins might also induce nausea in sensitive individuals on an empty stomach.

High Tannins in Other Foods

Besides wine and tea, high tannins are found in many other plant-based foods, impacting their flavor and texture. Examples include:

Unripe fruits: The puckering sensation in unripe bananas or persimmons is due to high tannins.
Nuts: Walnuts and acorns are high in tannins.
Dark chocolate: Tannins contribute to the characteristic bitterness of dark chocolate.
Legumes: Certain beans, particularly red ones, have high tannin levels.

The Double-Edged Sword: Health Effects of High Tannins

High tannin consumption can have both beneficial and adverse health effects. They act as potent antioxidants but can also hinder nutrient absorption.

Potential Health Benefits

Antioxidant and anti-inflammatory properties: As polyphenols, tannins combat free radicals and reduce inflammation. This is associated with a reduced risk of chronic diseases such as cardiovascular disease, cancer, and diabetes.
Antimicrobial effects: Tannins possess antimicrobial properties that can inhibit the growth of various microorganisms, including some bacteria and fungi.
Cardioprotective effects: Some tannins may help lower blood pressure and protect against heart disease.
Promote blood clotting: The astringent nature of tannins can help accelerate blood clotting.

Potential Side Effects

Iron absorption interference: Tannins can bind with non-heme iron from plant sources, impeding its absorption in the digestive tract. This is a concern for individuals with or at risk of iron deficiency.
Nausea and stomach irritation: Some sensitive individuals may experience stomach upset or nausea from consuming high-tannin beverages like strong tea on an empty stomach.
Nutrient absorption interference: Tannins can bind to other compounds, including proteins and carbohydrates, potentially reducing the nutritional value of foods.
Migraine triggers: Individuals sensitive to serotonin may experience migraines from high tannin intake, though further research is needed.

High-Tannin vs. Low-Tannin Foods: A Comparison


Feature	High-Tannin Foods & Drinks	Low-Tannin Foods & Drinks
Mouthfeel	Astringent, drying, rough, coarse	Smooth, soft, supple, light
Flavor	Bitter, complex, structured	Less bitter, often more fruit-forward
Example Wines	Cabernet Sauvignon, Syrah, Tannat	Pinot Noir, Grenache, Merlot
Example Teas	Black tea, oolong tea	White tea, herbal infusions
Other Food Examples	Walnuts, unripe fruits, dark chocolate	Soft cheeses, creamy sauces, salmon
Aging Potential (Wine)	High (tannins soften over time)	Lower (less structure for aging)

How to Manage Your Tannin Intake

For most individuals, a tannin-rich diet is healthy. However, if you have concerns about side effects or specific health conditions, you can manage your intake:

Eat with meals: Consuming high-tannin tea or wine with food can help reduce the risk of nausea. Proteins and carbohydrates in food can bind with tannins, lessening their direct impact on the digestive tract.
Time tea and iron-rich meals: If you have iron deficiency, drinking tea between meals rather than with them can help maximize iron absorption from plant-based foods.
Brew tea for less time: Shorter steeping times result in lower tannin concentration in tea.
Pair rich foods with high-tannin wines: This classic pairing balances the flavors and sensations of both the food and wine.
Process foods appropriately: Leaching, soaking, and boiling can reduce tannin content in certain foods like acorns.

Conclusion: Understanding the Impact of Tannins

High tannins significantly influence our sensory experience, especially in beverages like wine and tea, providing body, structure, and flavor complexity. Healthwise, they offer benefits through antioxidant and anti-inflammatory properties, but also potential drawbacks, notably affecting iron absorption. Understanding what high tannins do allows for a more informed approach to food and drink, enabling appreciation of their unique characteristics and management of their effects on the body. For a deeper scientific understanding of these plant compounds' effects, metabolism, and nutrition, comprehensive reviews are available. You can find a comprehensive review of bioactive tannins in foods and beverages, including detailed information on chemical structures and potential therapeutic applications, from sources like MDPI.

MDPI: A Comprehensive Review of Bioactive Tannins in Foods and Beverages

Frequently Asked Questions

If a wine has high tannins, it means it will likely have a more complex structure, feel full-bodied, and create a dry or coarse, puckering sensation in your mouth. These wines often have good aging potential, as the tannins will soften and mellow over time.

Yes, high tannins in tea can cause side effects for some people, including nausea or stomach upset, especially when consumed on an empty stomach. They can also interfere with the body's absorption of iron from plant-based foods.

Tannins offer both health benefits and potential drawbacks. They act as antioxidants with anti-inflammatory properties, potentially benefiting heart health. However, excessive intake can hinder nutrient absorption, especially iron, and may cause digestive discomfort in sensitive individuals.

To reduce the effects of high tannins, you can consume high-tannin foods and drinks with a meal, which helps the tannins bind to proteins and carbohydrates instead of affecting digestion. For tea, brewing for less time or adding milk can help. You can also choose lower-tannin options, like white wine instead of red.

Foods high in tannins include red wine, black tea, coffee, dark chocolate, walnuts, pomegranates, and unripe fruits like persimmons. The skins and seeds of many fruits and legumes also contain high tannin levels.

Tannins interfere with iron absorption by binding to iron in the digestive tract, forming a complex that the body cannot easily absorb. This primarily affects non-heme iron from plant-based sources and is a concern mainly for those with an existing iron deficiency.

While tannins don't have a flavor of their own, they contribute to the texture and overall impression of bitterness and astringency. They can also balance out sweet and fruity notes, adding complexity and preventing flavors from being too one-dimensional.