Bad breath - What actually causes it?
- In the majority of cases (85 to 90% of people who suffer with breath odors), the single most frequent causative agent of their halitosis is oral bacteria.
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Just imagine the smell of rotten eggs, feed lots, urine, feces, sweaty feat and rotting meat.
Now, imagine that all of these odors were mixed up into a single cocktail and you had to take a whiff. We'll, that's pretty much what you do every time you smell someone else's breath.
We didn't just make the list above up. The compound responsible for those stinky smells (see below) are found in everyone's breath.
And if their concentration is high enough, you'll have bad breath. Or, if you can keep their levels to a minimum, you won't. It's pretty much as simple as that.
Where do these compounds come from?
Just like humans, bacteria consume foods and, in turn, excrete waste byproducts.
As it happens, the waste products produced by some types of oral bacteria are smelly sulfur compounds. And it's these compounds that usually lie at the root of a person's breath problems.
Some of the most offensive smells you know are caused by sulfur compounds.
- The stench of rotten eggs is due to the compound hydrogen sulfide.
- The stinky smell that comes from feed lots and barnyards is created by the sulfur compound methyl mercaptan.
- The odor you associate with the ocean is partly due to the presence of dimethyl sulfide.
And while it may come as a complete surprise to you, each of these compounds is produced as a waste product by the bacteria that live in your mouth. And they escape with your breath every time you exhale.
Hydrogen and dimethyl sulfide account for about 90% of the volatile sulfur compounds found in breath. (Suzuki 2012) [reference sources]
Bad breath is caused by "volatile sulfur compounds" ...
Dentists refer to the sulfur byproducts excreted as waste by oral bacteria as "volatile sulfur compounds" (VSC's). And it's their presence in our breath that we detect as "bad" breath.
[The word "volatile" describes the fact that these compounds evaporate (transform into a gas) quickly, even at normal temperatures. It's this property that explains how these compounds are able to escape our mouth so quickly and easily.]
... as well as some other stinky molecules too.
While the VSC's listed above are generally considered to be the primary causative agents of bad breath, the bacteria that live in our mouth produce other waste products that can play a role too.
Some of these are compounds that are responsible (at least in part) for the odors listed below.
- Cadaverine - The smells associated with urine and decaying meat.
- Putrescine - The foul odor that comes from rotting meat.
- Skatole - The characteristic smell of human fecal matter.
- Isovaleric Acid - The smell of sweaty feet.
It all boils down to concentration.
This wonderful mix of smelly compounds is found in the breath of all humans, no one is an exception. Fortunately, at low levels they can't be detected by the human nose. It's only when their levels become elevated that others can detect them.
VSC's are produced by anaerobic oral bacteria.
Most of the compounds that cause bad breath are the byproducts of anaerobic bacteria (more specifically Gram-negative anaerobic bacteria). The term "anaerobic" describes the fact that these types of bacteria do best in environments that are devoid of oxygen.
The key is controlling the number of these bacteria that live in your mouth.
The human mouth is home to hundreds of different types of bacteria. And there's a constant battle for living space between the types that cause bad breath and those that don't. It's the precise balance between these two that ultimately determines the quality of a person's breath.
The role dental plaque plays.
The accumulation of dental plaque (the white film that forms on teeth both above and below the gum line and also on the tongue) can tip the scales in favor of odor-causing bacteria.
- A layer of plaque as thin as 0.1 to 0.2 millimeters (about the same thickness as a dollar bill) can be oxygen depleted, thus creating the precise type of environment in which anaerobic bacteria flourish.
- As more and more plaque builds up in a person's mouth, these bacteria gain more and more available living space, thus putting the person at greater risk for having bad breath.
What's the food source for these bacteria?
Most volatile sulfur compounds are the waste products created by anaerobic bacteria as they digest proteins.
That means, as we consume things like meat, poultry, fish, and dairy items the bacteria that live in our mouth get a meal too and subsequently producing the byproducts that cause our bad breath.
Even without an obvious source, like just having eaten something, it's not hard for anaerobic bacteria to find a meal.
- There are always protein sources floating around in our mouth, such as dead skin cells or some of the compounds that make up saliva.
- With lax brushers and flossers, there's always the leftover food debris from yesterday's meal, and the meal before that, and the one before that....
- Meat, fish and seafood, eggs, and dairy foods (milk, cheeses, and yogurt) are all obvious examples of foods that are high in protein. Most of us get about two thirds of our daily needs from them.
- Other sources include cereal grains (and cereal grain products), nuts, and the seeds from pod bearing plants (peas, beans, and lentils).
- Many deserts (cakes, pies, yogurt) often are surprisingly protein rich. (Often due to egg white or nut content.)
Where do these bacteria live?
As mentioned above, anaerobic bacteria do best in environments that are devoid of oxygen. And due to this fact, they're typically found in the greatest numbers in the hidden recesses of the mouth.
This includes the deep grooves of the tongue, areas in between teeth, and those spaces (periodontal pockets, see below) that form as a result of gum recession and bone damage caused by gum disease. They're also found in thick debris films such as the one that often covers the back portion of a person's tongue.
The most common cause of halitosis.
a) The tongue.
For most of us, the bacteria that cause our bad breath live on the surface of our tongue.
Think back to the breath testing experiments described at the beginning of this topic.
- While the smell emanating from the anterior portion of a person's tongue can be unpleasant, it usually it isn't the primary source of their breath problems.
- The most common odor-producing region of the tongue is the posterior (back) portion.
Do this check.
Go to a mirror, stick your tongue out and take a look at it. Most people will see a white coating on their tongue's surface. The further back (toward the throat) they look, the whiter this layer usually appears.
Smelly debris on the back part of the tongue.
This is dental plaque and it's chocked full of the types of anaerobic bacteria that cause bad breath.
The amount of buildup will vary.
The type of surface texture found on a person's tongue will influence the amount of coating that it tends to accumulate.
People who have a deeply grooved or furrowed tongue will be more likely to accumulate a bacterial-laden coating, as opposed to those who have one that has a smoother surface.
Research has shown that there is a direct correlation between the amount of coating that exists on a person's tongue and the total number of anaerobic bacteria that are present.
And as you can probably guess, when the anaerobic bacterial count on a person's tongue is reduced, there is usually a direct correlation, an improvement, in the quality of their breath.
(That's why tongue cleaning plays such an important role in curing bad breath.)
Odors can come from bacteria beneath the gum line.
b) Bacteria that live around teeth.
Bad-breath causing anaerobic bacteria can find a home in places around your teeth too.
When you floss, you may notice that you dredged up a foul odor or taste. This odor may be more noticeable as you floss between back teeth.
These locations are places where anaerobic bacteria have found a home. The taste and smell you get is evidence of this.
Gum disease forms deep pockets that are hard to clean.
The role of gum disease.
Even in relatively healthy mouths, anaerobic bacteria are able to find suitable (oxygen deprived) places to live. These types of locations are, however, more numerous and available in the mouths of people who have periodontal disease (gum disease).
That's because this condition causes damage to the gums and bone that surrounds a person's teeth, which results in the formation of deep spaces called "periodontal pockets."
These recesses can be difficult, if not impossible, to clean. And that makes them an ideal anaerobic environment for the types of bacteria that cause bad breath.
Our next page discusses risk factors for bad breath (smoking, dry mouth, gum disease, foods, medical conditions, dentures). These are the conditions that tip the scales in favor of your having breath odors.
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