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.

What?

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!

Foodborne diseases: The case of the innocent-looking berries

'Berries' by Jeremy Cherfas
under a CC license

It's been about two-and-a-half years now that cases of hepatitis A have been appearing in Europe. Further analysis, as quoted by the European Food Safety Authority, has shown similarities in the viral genome across the majority of those cases. That is an indication for a common source of infection, which - currently - is believed to be frozen berries. So far, 11 countries in Europe are known to have been affected. (A similar-sounding story that appeared in the US seemed to be coincidental and it was attributed to imported pomegranate seeds.)

Technically, the term "berries" covers a wide variety of fruits although it is normally used to describe small, juicy, bright-coloured fruits, such as blueberries, strawberries, blackberries, blackcurrant, etc. They can be eaten raw but they are also extensively used as ingredients either raw or as preserves in other foodstuffs, such as creamy desserts, parties, flavoured ice-creams, various alcoholic beverages, etc.

In some of those products the berries find themselves in having had minimal - and sometimes non-thermal - treatment. That provides ground for pathogens and, in the case of hepatitis A, the hepatitis virus that may lie on the surface to survive.

Locations of the hepatitis A outbreaks attributed
to a common, continuous source in the EU/EEA,
possibly frozen berries; Compiled from Source:
European Centre for Disease Prevention and
Control and the European Food Safety
Authority,  2014; Outbreak of hepatitis A in
EU/EEA countries - Second update. EFSA
supporting publication 2014:EN-581. 14 pp.

Hepatitis A is a disease usually transmitted via the consumption of food or water contaminated by infected fecal matter. It has a very long incubation period that can reach up to 50 days and, in some cases, it is asymptomatic, i.e., the people infected do not display any symptoms of illness (but they can transmit the virus).

While the food law in Europe requires food businesses to keep traceability records when receiving or providing food products or ingredients to other food business operators, including retailers, linking the hepatitis A outbreaks to a particular contaminated ingredient and tracing it back to a single source has proven to be very challenging.

The main reasons for that are the long incubation period of the disease and the complexity of the food chain, especially when dealing with multi-ingredients food products. Thus, when a case of hepatitis A is confirmed, pinpointing the source of the infection would require the patient to identify foodstuffs he/ she had consumed over a very long time (up to 50 days before the onset of symptoms), an exercise that is nearly impossible to execute in a fully accurate way. Then the ingredients and the processing of the individual foods needs to be considered in order to select the ones likely to have been vehicles for the virus. Then those should be traced back the food chain. With luck, superimposing the trace-back routes of different cases infected by the same virus strain could, at some point, help identify the starting point of the contamination.

Although hepatitis A is not normally a deadly disease (for reasonably healthy adults), it can be a rather "unpleasant" experience. Thankfully, consumers can minimise the risk by boiling frozen berries for about one minute; this will destroy the virus if present on the berries. Simply rinsing the berries with tap water may not be enough; depending on the type of the berries, they may have a large total surface with lots of niches where water cannot really reach (not to mention that fruits tend to have a hydrophobic surface... which reminds me of an older - yet irrelevant - post).

Moral line of the story - if there needs to be one: Risk communication, i.e., telling consumers (and businesses) what the hazard, the risk and the reasonable mitigation measures are, preferably in plain language, can be very effective when everything else fails.

Dinner table: Food for thought

'Dinner table settings'
by joeywan under a CC license

For the part of the world that is lucky enough to have secured a minimum amount of food on a daily basis, the dinner table may feel like the reasonable place to end the daily routine.

In fact, though, the dinner table is much more than that. It's the place to talk with family and friends. It's the place to listen to others. It's the place to get to know people. It's the place for all emotions, from sorrow to happiness and from anticipation to excitement. It's the place to secure a deal, explore arguments, brainstorm on ideas, announce plans and... well... eat.

The latter, quite rightfully, sounds like stating the obvious. However, what I'm really trying to say is that, food-wise, the dinner table is challenging in many different ways. While, normally, we tend to focus either on the social dimension of eating or on satisfying the physical need to eat, getting things in order for a dinner table (or any meal, in fact) is not that simple a process. Indicatively, consider the following elements:

• General food safety; are the raw materials safe, has the food been handled properly, etc.
• Food allergens; is the food OK for the people that will consume it with respect to allergens, does one of them has an allergy on one of the ingredients used, is it likely to have allergens present through contamination, etc.
• Nutrition; does the meal provide what is needed for all its intended consumers, does it provide variety under the "balanced nutrition" rationale, etc.
• Special dietary needs; are they known for each of those consuming the meal, are cultural or religious-based dietary needs also considered, are they properly addressed altogether, etc.
• Acceptance; are the meal elements acceptable at the sensory level, i.e., do they look nice, do they have an appealing flavour and taste, etc.
• Novelty; is the meal intriguing or interesting for those who will consume it (not necessarily in the sense of 'food innovation')?

'Table' by anthimeria
under a CC license

Don't consider that list as exhaustive. It's not. Not even close. What is interesting is that each of the points above is close to being a science on its own.  And what is challenging is that for each of the points above there is still much to investigate and learn (at the scientific level).

Most of you will argue that although we normally eat on a daily basis in our lives the food we consume rarely causes problems. That is a fair point. But:

• The reaction of people to unsafe food depends on their overall health status and the factor that makes the food in question unsafe. Pathogens like listeria monocytogenes tends to be more of a concern for immunosuppressed individuals and pregnant women but there are food-borne pathogens that much more aggressive. Contaminants of chemical or biological nature may or may not lead to acute effects, depending on the type of agent, the amount consumed, etc. The impact of the consumption of unsafe food on human health and well-being in the long run is not always very easy to calculate. Besides that, most food-related incidents tend to be downplayed (e.g., an upset stomach or a single diarrhea incident is normally ignored) so the exact impact of non-safe food is likely under-estimated.
• Food allergy is not that rare. It 's impact on the individual depends on the level of sensitisation for the allergen in question and the amount consumed but in some cases it can be life-threatening.
• Good nutrition is a standing challenge. Nutrient needs vary depending on both genetic factors, age, health status, life-style choices and cultural background. Beyond that, there are people with special dietary needs, who need to abstain from certain ingredients or require more or less from specific ingredients. For instance, coeliacs must follow a gluten-free diet. To make things more complicated, the availability of each nutrient is a dish depends on several factors, including the nutrient form in the food, the food matrix (i.e., where is the nutrient contained), the presence of other ingredients (e.g., a nutrient may become partially "out of reach" to the digestive system in the presence of specific ingredients).
• Acceptance for both "normal" and "novel" foods is a relatively new niche for studies under food science. There is still a lot to learn on how people make choices for food and towards what result. It is not always the question of whether the food smells, tastes and "feels" good, though. Cultural background, habit or past personal experiences, amongst others, can make people like or detest certain foodstuffs.

I'm not suggesting or implying that the person who cooks dinner should get a food science degree. I'm merely pointing out that there is really a lot to learn for something many of us normally take for granted.