Green Tea Science Part 2: Tannin, and Gallic Acid - 7 Commonly Asked Questions and How You Can Benefit

Polyphenols, or phytochemicals, are a class of micronutrients found in plants. Polyphenols act as chelators to remove toxic metals from the blood stream and tissues and are also considered to be one of the most powerful antioxidants. Scientists have discovered over 4000 polyphenol compounds including tannins and gallic acid, which are a subset of polyphenols. When polyphenols, such as tannins and gallic acid, are combined, naturally or synthetically, they work synergistically to provide more potent benefits. Gallic acid is considered a subtype of tannins and while gallic acid and tannins share similar molecular structures in their organic forms, tannins are converted into gallic acid when consumed, due to oxidization of the tannin molecules.

Tannins are plant-derived organic compounds found in bark, fruit skins, seeds, tea leaves and other plant sources. Tannins have been shown to contain antimicrobial, antiviral and antifungal properties. As a potent antioxidant, tannins provide protection from the oxidization of cells caused by free radicals. This benefit, in addition to tannins ability to reduce inflammation and prevent gene mutation may protect against the development of certain cancers. Tannins may also be useful as a dietary aid for weight-loss due to their interference with the conversion of certain nutrients and food substances during the digestive process.

Gallic acids, also called hydroxybenzoic acids, are colorless naturally-occuring crystalline compounds found in all plants. Abundant sources include blueberries, flaxseeds, and tea leaves. As an antioxidant, gallic acid provides cellular protection from free radicals. Gallic acid has also proven to be an effective anti-inflammatory agent and may reduce the symptoms of arthritis, lupus, and other inflammatory conditions such as allergies. Gallic acid promotes the release of insulin and is being studied for its potential benefit in the treatment and prevention of diabetes. It addition to its direct health benefits when consumed, gallic acid also provides protection against aflatoxins produced by fungus during storage and is used to preserve foods such as corn, wheat and nuts, which are susceptible to aflatoxin contamination. Gallic acid's antifungal properties not only fight fungus in the gut when consumed but also acts as a natural preservative for green tea as well.

Tannin and gallic acid levels are dependent upon many factors including harvesting times and methods. Green tea typically contains up to .46 mg of gallic acid per gram, compared to 4.65 mg for black tea and .68 mg for Oolong tea. Blackberries and red wine each contain an average of 4 mg of gallic acid, while apples, soybeans, and bananas contain close to 1 mg of gallic acid. By weight, green tea provides one of the highest sources of bioeffective tannin and gallic acid.

With potent antioxidants and other health benefits associated with tannins and gallic acid, these micronutrients are appropriate for just about anyone interested in improving and maintaining health. Individuals interested in a healthy approach to weight loss may also benefit from tannin's and gallic acid's ability to curb hunger. High concentrations of these compounds may affect important enzyme levels in fetuses, and pregnant women should consult with their primary care provider before taking supplementary forms of tannins or gallic acid. However, there are no known risks with moderate consumption in a natural form such as fruits and green tea.

Side effects of tannins and gallic acid are uncommon and are usually associated with over-consumption or other underlying health conditions. Nausea, headache and stomach irritation are the most common side-effects reported by a small number of consumers. Excessive tannins in the diet may interfere with the body's ability to absorb iron in people with marginal iron levels but scientific studies are still inconclusive. Tannins and gallic acid are also being studied for their possible potentiating effects on pharmaceuticals. Individuals taking prescribed and over-the-counter medications should consult with their primary care provider with any concerns about possible interactions.

Polyphenols consumed from a naturally-derived source, like Issaku Japanese Green Tea, provide the greatest levels of bioavailability and bioeffenciency, which is directly related to the absorption of micronutrients. According to studies published in The American Journal of Clinical Nutrition, dietary polyphenol supplements may be useful when consumed in moderate levels but are inferior to unsynthesized compounds. Infusions and tinctures may provide the most effective delivery of the beneficial constituents found in polyphenols and nutritionists recommend incorporating these sources of polyphenols into a regular diet for long-term health benefits. 

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