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Bad breath from proteins? Green tea helps

The polyphenols in green tea can help solve a problem that many athletes on a protein-rich diet are familiar with: bad breath. A Japanese study on the subject, published in the Journal of Nutritional Science and Vitaminology, shows that substances in green tea such as EGCG [structure shown below] inhibit the production of sulphurous gases by micro-organisms in the mouth.

Complete proteins contain the amino acids methionine and cysteine. These amino acids are also found in dead cell material in the mouth.

Organisms that live in the mouth cavity bacteria such as Streptococcus are well-known examples use these amino acids to produce sulphurous gases like hydrogen sulphide [H2S] and methanethiol [CH3SH]. If you exhale large quantities of these gases chances are you have bad breath.

Hydrogen sulphide smells of rotten eggs, methanethiol smells like a marsh with lots of decaying organic material. If you eat a lot of animal protein, these gases are probably present in high concentrations in your breath. And products that leave a thin film of proteins behind in your mouth and throat can really mess up your breath - shakes and quark for instance.

Substances such as EGCG probably inhibit the formation of sulphurous gases. EGCG is toxic to streptococci, and because the latter also cause cavities in your teeth, EGCG can also have a catabolic effect on your dentist's bill. Surely then it's logical that green tea would promote fresh breath?

To test the theory the researchers did a study on fifteen test subjects whose breath stank of rotten eggs and fetid swamps. They got the test subjects to brush their teeth, chew sugar-free chewing gum, suck peppermints, chew parsley seed - or keep a couple of teaspoons of green tea powder in their mouth for two minutes. The amount of polyphenols in the powder was about seven hundred milligrams, the equivalent of seven cups of green tea.

Afterwards the researchers measured the concentration of sulphurous gases in the test subjects' breath. The figure below illustrates the effect right after the treatment.

Bad breath from proteins? Green tea helps

Those who had used green tea powder had a considerably lower concentration of sulphurous gas in their breath. The effect is fairly short-lived however.

The worst smelling gas in the breath is the marsh gas methanethiol. Fortunately green tea has a longer lasting effect on this foul-smelling gas in the breath it still works after an hour. See the table below.

Bad breath from proteins? Green tea helps

The effect of green tea powder on hydrogen sulphide [rotten eggs] lasts much less long, as you can see below.

Bad breath from proteins? Green tea helps

Proteins neutralise the polyphenols in green tea. The effect of green tea on the breath is therefore stronger the less food remains there are in your mouth.

Bad breath is not only a social problem, but it is not healthy for your mouth. Sulphurous gases inhibit the growth of connective tissue.

J Nutr Sci Vitaminol (Tokyo). 2008 Feb;54(1):89-94.