Vacuuming may affect our microbiomes

The westernized lifestyle includes something that we often do not realize is a more important part of our life than it was to people hundreds of years ago: cleaning. With newly developed technology, like vacuuming, we are able to maintain cleaner homes, but this has also increased exposure to allergens such as dust mites. Allergens have a proven impact on the immune system of exposed persons, and as we have seen, the microbiome and the immune system are closely linked. The work of certain Norwegian scientists, published by Microbiome, explores the significance of washing and vacuum cleaning on the gut microbiome of mothers and their children.

The study group included 358 mother-child pairs that were included in a controlled non-randomized longitudinal study called IMPACT (Immunology and Microbiology in Prevention of Allergy among Children in Trondheim). Data was tested for the pregnant woman and then their two-year-old children (two years later). Average cleaning frequencies were 2.9 washings and 6.6 vacuum cleanings per month. For pregnant women, increase in Faecalibacterium prausnitzii showed the strongest association with increased vacuum cleaning frequency in once statistical model, while Roseburia faecis was found to have the strongest association in another statistical model. For the 2-year-old children, the Blautia species in one model, and the Oscillospria species in a second model, were identified as significant.

While the results of this study are a bit confusing, the main point is that the indoor household environment, including hygienic behavior, could have a potentially significant influence on the adult gut microbiome. High frequency of vacuuming could increase allergen presence in the air, which, when breathed in, could go on to influence the immune system – and therefore the microbiome. While many other environmental factors could not be controlled for in this study, the results do bring up the possibility of allergen and microbiota association.       

Red wine and coffee modulate the microbiome

Prebiotics are foods that alter the microbiome.  They are important to many potential microbiome therapeutics because they could be used to shift the microbiome from a dysbiotic, or unhealthy state, to a normal healthy state.  Most scientists that study prebiotics investigate indigestible fiber, because these are known to survive digestion are broken down by specific microbes, thus predictably selecting for specific organisms’ growth.  Recently though, other prebiotics are being studied.  A major class of these are polyphenolic compounds, which provide the antioxidant characteristics of plant material.  Last week researchers from Spain studied the shift in the microbiome that may be induced by red wine and coffee in particular.  They published their results in the journal Food & Function.

The researchers studied 23 patients that had allergic rhinosinusitis or asthma as well as 22 age-matched controls.  They chose individuals with autoimmune diseases because of the promise of prebiotics affecting their diseases.  They asked all of the individuals to fill out a food survey of what they had eaten in the past year, and how often they ate it.  After, the scientists took samples of their feces and measured the bacteria within it.  The scientists found that the abundance of Clostridium, Lactococcus and Lactobacillus was directly associated with polyphenol intake from coffee, and that Bacteroides was positively associated with red wine consumption.  Unfortunately, they noted that these did not differ between allergic people and healthy ones.

This study was certainly lacking in its scope and rigor.  It did not attempt any interventional studies to controllably reproduce these effects, and it did not identifiy specific polyphenols that are responsible.  Nonetheless, it does begin to define how alternative prebiotics may affect our microbiome.  Polyphenols in particular are linked to all sorts of health benefits, normally attributed to their anti-oxidation, however perhaps they positively impact the microbiome as well. 

Hand washing dishes may decrease risk of allergies

A study published on Monday by the journal Pediatrics has gotten a lot of press this week because it shows a connection between allergies in children and the method by which parents wash their dishes. Parents, especially new parents, often consider good hygiene as one of the most important factors in raising their new child, but according to the hygiene hypothesis it may be true that too much cleanliness actually negatively affects a young child.  Asthma, eczema, and other autoimmune diseases are becoming more common conditions in children, and each has been linked to the hygiene hypothesis.  Researchers in Sweden reinforced this link when they discovered a possible connection between allergies in children and whether dishes were washed by hand (less clean) or by machine (more clean) in their homes.

 The researchers sent a questionnaire to parents of children aged 7-8 which was filled out by 717 families in Molndal, Sweden and 312 families in Kiruna, Sweden. The questionnaire asked many questions pertaining to the children, including previous symptoms of asthma or eczema, method of washing dishes, and if their food was farm grown or fermented.  When examining the results it is important to remember that all forms of bias cannot be eliminated when doing surveys, because, among other reasons, it is difficult to get a perfectly random sample.

Results of the study showed that there were lower instances of allergies in children whose families washed their dishes mainly by hand rather than by machine. In addition, this effect was amplified if the children ate food that was either fermented or purchased from a farm (both of which should introduce diverse bacteria to the children).  Of course, there were other variables that were not inquired in the questionnaire that are also known to decrease rates of allergies in children, and which may be related to washing dishes by hand, for example a lower socioeconomic status.  Then again, the authors suggest that hand washing dishes may reasonably be responsible for these lower rates of allergies in children of lower socioeconomic status.

So, you may be wondering how exactly this pertains to the microbiome. Hand washing dishes cleans less thoroughly than highly efficient machines, which sounds gross, but the exposure to more microbes when you are young may help develop the microbiome and immune system.  While this study is not perfect, it still shows us that exposure to bacteria is potentially a good thing for the new and developing microbiome. 

Treating severe nickel allergies with probiotics

Buffalo nickel, made of 25% nickel.

Systematic nickel allergy syndrome (SNAS) is a severe reaction to nickel, a metal that is found in nature and most human food sources. An allergic reaction to nickel can manifest cutaneously, causing inflammation and irritation of the skin, or it can be gastrointestinal, causing diarrhea. Studies in which balanced diets are used as a way of reintroducing nickel to SNAS patients have been conducted to find possible treatments of this allergy; however no cure has been found. Research by a group in Italy was published last month in the Journal of Applied Microbiology that examined the use of probiotics such as Lactobacillus reuteri to treat SNAS patients.

A double blind study was performed using twenty-two adult women who had both systematic and cutaneous reactions to nickel. A control group received a placebo, while an experimental group received the L. reuteri probiotic. Fecal sampling and clinical evaluations were performed at the start of the study, before any pills were taken, as well as after two weeks of supplementation and two weeks after the end of the trial. Throughout the entire evaluation period the patients followed a low-nickel diet.

Both groups prior to experimentation had low diversity of lactic acid bacteria (LAB) communities in their gut.  After the trial, they found that the control group had stable LAB communities while the experimental group resulted in greater diversity of LAB than prior to the study. They found that only the experimental group showed the presence of L. reuteri meaning that the bacteria in the probiotic had successfully colonized and survived in the gut, an essential feature if a probiotic is to be used in a clinical setting.

They also found a significant improvement in cutaneous symptoms after two weeks in both the group being given the probiotic with a low-nickel diet, as well as the strictly low-nickel diet patient group, however the improvement was more pronounced in the group getting the probiotic. Only patients receiving the supplementary L. reuteri showed a significant reduction in gastrointestinal symptoms. Eating a diet low in nickel will cause less averse reactions than an uncontrolled diet; however, this study strongly suggests that probiotics can significantly decrease the severity of allergy symptoms in SNAS patients. The study also suggests that a combination of diet and probiotics could increase bacteria’s ability to colonize in the intestines. Further long-term studies on the prolonged effects of probiotic use in treating SNAS and other conditions will allow us to better understand how to use probiotics to manipulate the microbiome and treat disease. 

Yet another link between allergies and the microbiome

A new study out in PNAS describes how gut bacteria in mice were responsible for protecting their host from peanut allergies.  In the study gnotobiotic (germ-free) mice which were peanut-sensitive were inoculated with various bacterial strains.  While some of the strains had no impact on the inflammation caused by peanuts, others, from the genus Clostridia (yeah, the same one as C. Difficile) actually prevented inflammation.  The researchers are hoping to discover a metabolite created by Clostridia that was responsible.  A nice longer form article about the paper was published by the BBC.