When you take a sip of a dry red wine, that astringent feeling in your mouth comes from the grape’s naturally occurring tannins. Tannins in red wine, tea and coffee give them their bitter flavor and drying sensation.
Really, tannic acid is meant to make plants undesirable to potential invaders, but they can be quite pleasant in certain foods and drinks. Plus, these polyphenols are loaded with health-promoting antioxidants, and they may even boost the health of your immune and cardiovascular systems.
What Are Tannins? What Do They Do? Where Do They Come From?
Tannins (also called tannic acid) refer to a type of water-soluble polyphenol compound that’s found in nature. They have bitter and astringent properties that exist to protect plants, making them unpalatable to potential invaders.
They’re found in plant fruits, wood, bark and leaves.
Although tannins are meant to be unpalatable in nature, they can also offer pleasant flavors when managed properly.
You know that bitter, yet satisfying flavor in coffee or dark chocolate? That comes from the tannins.
In the world of winemaking, tannins are used to add complexity to the flavor and texture of red wines.
Tannin is a general term used for phenolic compounds. There are two major groups of plant tannins: proanthocyanidins and hydrolysables.
Tannins work by binding to proteins in our saliva and separating them, which is what causes the dry mouth sensation you get when drinking or eating foods high in tannins.
Tannins in Wine and Other Food Sources
Wines that are high in tannins will leave you with a dry-mouth sensation — these are typically called tannic wines.
Wine tannins are highest in reds, but some white wines have the polyphenols too.
Red wines are some of the most astringent foods because in the wine-making process, the grape juices are in contact with the tannin-rich grape skins for a longer period of time. This is called maceration, and the length of this process determines the tannic acid content in wine.
Tannins in wood barrels also dissolve into wine through contact.
Wine-makers use oak barrels for their unique and pleasant flavored tannins. Even adding tannin powders and oak chips to alcohol and water when making wine is growing in popularity because it increases the taste of wood tannins without the expense of oak barrel storage.
In addition to tannins in wine, the polyphenols can also be found in the following foods sources:
- Green tea
- Black tea
- Red wine
- Acai berries
- Red beans
Tannins in tea and other bitter, astringent foods and beverages contribute to their complex flavors and the dry-mouth feel you can get when consuming them. Tannins in beer also exist, although brewers typically try to avoid the bitter flavor that they cause.
The tannins in hops, barley seeds and oak barrels are absorbed by the liquid during the boiling process. It’s normal to have some tannic acid in beer, but too much can lead to excessive bitterness.
Sometimes, tannins are found in water too. This is due to a natural fermentation process that occurs when water passes through soil or decaying vegetation.
When tannic acid is in water, it may create a yellow color, much like a light tea.
Some people enjoy the bitter flavor of tannins in coffee, dark chocolate and other foods, while others opt for sweeter foods instead.
Potential Health Benefits
1. Contain Antioxidants
Tannic acid is a polyphenol that works to reduce oxidative stress and free radical damage to our cells. In fact, winemakers love that tannic wines are protected by their natural antioxidants.
An animal study published in the European Journal of Nutrition found that dietary tannic acid can modulate damage in the gastrointestinal tract of rodents. Researchers determined that consuming polyphenols and tannins may have protective and therapeutic potential in oxidative damage-related conditions.
Because tannic acid reduces oxidative stress, it may also work to decrease inflammation and improve symptoms of inflammatory conditions. Some studies suggest that tannins have anticarcinogenic potential, which may be related to their antioxidative properties and ability to protect cells from oxidative damage.
2. Have Antimicrobial and Antiviral Effects
Tannins are well-known for their antimicrobial activities, and they may improve your immune response. According to research conducted at the University of Memphis, the growth of many fungi, yeasts, bacteria and viruses is inhibited by tannic acid.
Studies also show that tannins in plants are able to inhibit foodborne and aquatic bacteria. This allows tannins in fruits to serve as a natural defense mechanism against microbial infections.
Tannic acid is used in food processing to increase shelf life as well.
3. May Play a Role in Diabetes
Tannin uses include the ability to help balance blood sugar levels. According to a 2018 study published in Current Medicinal Chemistry, tannic acid may be useful for prevention and management of type 2 diabetes.
Researchers analyzed the therapeutic effects of tannic acid by gathering more than 41 medicinal plants containing tannins and 19 isolated tannins and tannin-rich crud extracts. The pharmacological studies involving these samples indicated that the compounds possess glucose-lowering effects.
4. Improve High Blood Pressure
A 2015 study conducted on hypertensive rats found that tannic acid was able to decrease blood pressure values. Researchers were able to establish that tannic acid has antihypertensive and vasodilator effects.
This means that consuming tannin foods may help improve your heart health, but human studies are needed to determine the full potential of tannic acid for the cardiovascular system.
5. Promote Blood Clotting
Tannic acid and other polyphenols are able to promote blood clotting, which may help to speed up wound healing.
One study published in Evidence-Based Complementary and Alternative Medicine found that green tea extract high in tannic acid contributed to a significant decline in bleeding of the socket caused by tooth extractions. It also helped reduce oozing after the procedure.
The green tea tannins caused a contraction of damaged tissue and capillaries because of their astringent effects. Researchers suggest that the use of tannic acid compounds are among the best topical treatments for the cessation of bleeding because of these beneficial activities.
Risks and Side Effects
Are tannins bad for you?
For some people, tannin side effects can include headaches or migraines. This doesn’t happen to everyone who drinks high-tannin wines or other food sources, but some are more sensitive to the compound than others.
More research is needed to understand if this is due to a tannin allergy or some other mechanism that leads to headaches, but if you notice pain after consuming tannic acid sources, then try avoiding them.
- Tannins are polyphenol compounds that add a bitter flavor and astringent texture to foods and drinks.
- What drinks contain tannins? They can be found in wine, beer, coffee and tea.
- Tannic acid is also present in grapes, cranberries, nuts and some beans.
- Although some people experience tannin side effects, like headaches, the compounds have health benefits, including regulating blood sugar levels, promoting blood clotting, fighting infections and reducing free radical damage.