Chronic bad breath, or halitosis as it is known professionally, is a major problem for many people, regardless of age.
In 85% of cases, the problem is caused by bacteria in the grooves on the upper surface of the back 1/3 of the tongue. These are so-called gram-negative anaerobic bacteria (i.e. bacteria that live in an oxygen-free environment) that live in the very deep grooves of the tongue. Unfortunately, a toothbrush cannot remove them because they are simply too deep in the tongue grooves.
What causes bad breath is sulfurous fumes produced by bacteria breaking down amino acids containing sulfur atoms. These are the same chemical processes that take place in a sewer.
Therefore, if you are on a low cab- high protein diet, you could aggravate bad breath by getting a lot of amino acids, i.e. protein.
The mechanism behind the development of bad breath
There are two main players in the development of bad breath and they are two different types of bacteria working together.
One type of bacteria is the one that produces sulfur dioxide and the other type of bacteria is the one that helps to break down carbohydrate side chains.
So the problem of bad breath is much more complex than you might think.
Most of the amino acids supplied come from the diet in the form of glycoproteins, i.e. proteins with carbohydrate side chains.
The carbohydrate side chains have to be cut off before the anaerobic bacteria mentioned above can break them down into sulfur vapors (called VSC: volatile sulphuric compounds).
This "cutting" is done by an enzyme called beta-galactosidase. It is an enzyme produced by other bacteria on the surface of the tongue, and is quite differently accessible to the toothbrush, but can also be affected by the composition of your oral bacteria.
Link to periodontal disease
The bacteria that produce the sulfur fungi that cause bad breath are the same ones that cause periodontal disease (gum disease), so the two conditions are linked. This is important because it means that even if periodontitis is brought under control, the bacteria hiding in the deep grooves of the tongue could act as a reservoir for renewed worsening of the periodontitis condition.
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The composition of the oral bacteria is influenced by the factors described under "Oral biofilm", but can also be positively influenced, for example, by oral probiotics, i.e. positive bacteria that can outcompete the bacteria causing bad breath.