Sunday, 25 January 2015

Mouthwash: A case of disrupting the balance of the human-hosted bacterial ecosystem

It is well known the our bodies are inhabited by billions of microorganisms, mostly bacteria. The majority of those are benign and don't pose any threat to us, provided that we are reasonably healthy. Having said that, current thinking suggests that maintaining one 's health is tightly connected to the maintenance of properly functioning bacterial communities in our bodies.
'Vintage 80's Scope Mouthwash'
by twitchery under a CC license

Most of the things we do in our normal life affect the microorganisms living within us. Whatever we eat, for instance, affects our gut flora. Eating food with lots of fibre equals giving more food to the microrganisms of the gut - it may be even possible to fine tune gut flora this way. Showering and bathing alter the composition of our skin microbiota (there are times when clean skin becomes too clean, in a risky kind of way). Brushing our teeth changes the bacterial demographics of the oral cavity, etc.

Some - and, hopefully, most - of those changes have negligible effect of human health. Major disruptions, however, may lead to more pronounced outcomes. For instance, courses of antibiotics strongly reduce the gut flora populations, leaving ground for more resistant species to settle in and, if the are pathogens, to cause trouble to their host.

A common practice with potentially detrimental effects, which seems to go unnoticed, is the use of mouthwashs. Some of those, strongly impact the baterial populations within the mouth. That is a good thing if we are talking about bacteria that cause cavities or gingivitis but probably not so good if we are talking about the bacteria that can reduce dietary nitrate to nitrite.


OK, let's have a quick close look at that.

The topic of dietary nitrite (which originates from the nitrate that exists in foods, mostly leafy vegetables, which is converted to nitrite by the mouth bacteria) is still a bit controversial. The reason for that is that nitrites, which are further converted to nitrous oxide in the acidic environment of the stomach, can have good properties but also, possibly, some bad ones.

The good ones have to do with the function of the immune system, especially the organism 's defence in the gastrointestinal track against pathogens, the function of the cardiovascular system (improving blood flow, lowering blood pressure) and also the improvement of performance in moderate aerobic exercise. The bad ones are associated with cases where nitrosamine is formed, which is a carcinogen. The latter is, of course, of great concern. Nitrosamine can be formed by nitrites in the presence of secondary amines under the effect of high temperature or strongly acidic environment. Adding antioxidants (such as ascorbic acid) or keeping food processing temperature at lower level can help reduce considerably foodborne nitrosamine. Practically, nitrosamine levels from food intake are very low, though (e.g., considerably lower than the nitrosamine smokers receive from tobacco products).

So what is the bottom line?

As usual, it is a question of the right balance (as in the case of nutrition). Some mouthwashes can have an effect on nitrate-reducing bacteria and that may be not-so-good. But there may be very good reason to use them. Dental or gum problems pose considerable risks both in the long and in the short term. Really, a dentist should be the one to advise. Under normal circumstances, however, I thing that not overdoing it is quite important!

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