Tannins intolerance

Tannins are water-soluble polyphenols that are present in many plant foods and affect the nutritional value of foods or beverages because they bind to proteins. Most plants contain tannins however algae, fungi and mosses contain very little.

While generally safe for humans, in animals, tannins can impair the digestibility of food. They can contribute an astringent taste to the foods in which they are found but also play a role in the pigment of flowers and leaves. They are known to possess antibacterial, antifungal, anti-inflammatory, antiviral and anti-haemorrhagic (prevent easy bleeding) properties.

The growth of many fungi, yeasts, bacteria, and viruses are inhibited by natural food tannins but eating too much of them without vitamin C can cause some health issues.

Symptoms of tannin intolerance

• Bezoar formation (an intestinal obstruction)
• Bowel irritation
• Gastrointestinal pain
• Headache
• Irritation of the stomach lining
• Kidney irritation
• Liver damage
• Migraine

Foods and drinks rich in tannins

NOTE: Tannins are more concentrated in the skins of fruits and nuts especially red and dark coloured fruits. Tannins can inhibit the absorption of vitamin B12 and iron.

With the exception of tea, long-term or excessive use of herbs containing high concentrations of tannins is not recommended. A correlation has been made between the above symptoms and nasal, oesophageal and throat cancer in humans and regular consumption of certain medicinal herbs with high tannin concentrations. All the following herbs should not be used over long periods on a daily basis.

Herbs and spices that contain high levels of tannins

If ingested in excessive quantities, tannins also inhibit the absorption of minerals such as iron, which may, if prolonged, lead to anaemia. In order to prevent these problems, it is advised to drink tea between meals, not during. Foods rich in vitamin C help neutralise tannin’s effects on iron absorption. Adding lemon juice to tea will reduce the negative effect of tannins in iron absorption as well.

Many foods contain the added artificial tannins annatto. Annatto food colouring is designated as E160b. It can be further categorised as either E160b(i) (annatto bixin) or E160b(ii) (annatto norbixin). These extracts are used to provide a yellow or orange colour to various foods

Some products have been produced with tannin leaching from the wood during storage which has been shown to be detrimental to the health.

Food and drinks that may contain artificial tannins

• Baked goods
• Berry juice
• Black tea
• Butter
• Carob bean products
• Cheese
• Chocolate
• Cocoa
• Desserts
• Fruit fillings
• Grape juice
• Margerine
• Orange juice
• Processed meats
• Smoked fish
• Sour cream
• Wood-aged beer, cider, red and white wines or spirits
• Wood smoked meat and fish
• Yoghurt

Tannins have been associated with fatal liver damage from extensive use on burns or in enemas. However, the toxicity may be due to an impurity, digallic acid, rather than the tannins themselves.

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