Tannins

Tannin Definition

Tannin is any polyphenolic compound that forms strong complexes with proteins and other large molecules ^[4]. The word tannin originates from “tanning”, a leather production by soaking animal skins in plant extracts containing tannins ^[4]. Tannins are polyphenols that give bitter taste and mouth-drying effect to the plant foods.

Tannins Types

• Hydrolyzable tannins are esters of gallic acid (gallotannins) or ellagic acid (ellagitannins) and sugars.
• Non-hydrolyzable or condensed tannins or proanthocyanidins consist of flavan-3-ols. They include procyanidins, and prodelphinidins.
• Derived tannins formed during food processing such as theaflavins and thearubigins in black tea or oolong tea.
• Tannic acid extracted from nutgalls.
• Oligostilbenoids
• Reference: ^[4,7]

Foods High in Tannins

• Red wine
• Green tea, black tea, oolong tea
• Chocolate, cocoa
• Acorns
• Unripe fruits: pomegranate, persimmon
• Berries: strawberries, cranberries, blueberries
• Apples with skin
• Grapes, especially grape seeds and skins
• Nuts: hazelnuts, walnuts, pecans
• Spices: cloves, thyme, cumin, vanilla, cinnamon
• Beans: red beans, acacia
• Coffee
• Beer
• Sorghum
• Smoked fish and meat
• Reference: ^[4]

Tannins as Food Additives

Tannic acid is used as a clarifying agent or dye in fruit juices, soft drinks and alcoholic drinks.

Tannin Supplements

Various non prescription (over-the-counter) oral tannin supplements are available.

Tannins Health Benefits

There is INSUFFICIENT EVIDENCE about the effectiveness of tannins in the prevention or treatment of cancer ^[1] or high blood pressure ^[2] and hemochromatosis ^[3].

Tannins Safety: Side Effects, Toxicity

Side effects may include nausea, vomiting, diarrhea.

Tannins ingested in large amounts may reduce the absorption of the non-heme iron from plant sources, not iron from animal foods ^[5]. Tannins may reduce the absorption of certain medications.