Several studies have linked our lifestyle to gut microbiota composition. Factors such as continuous stress, an unbalanced diet rich in fats or sedentary habits, among others, are believed to be linked to our gut’s collection of microbes. The underlying mechanisms of this, however, were not fully understood.

Now, new research published in Cell Reports suggests the reason why Western lifestyle may reduce the variety of bacteria and alter the overall composition of gut microbiota is because it limits bacterial ability to be transmitted from human to human.

Led by the study’s senior author Jens Walter of the University of Alberta Department of Agricultural, Food & Nutritional Science, the researchers analysed the faeces of adults living in the US and people from rural agricultural-based Papua New Guinea, which remains one of the least urbanised countries in the world. They found that although both Americans and Papua New Guineans had many important microbe species in common, the former lacked 50 bacterial types in comparison to the latter.

The authors of the study wanted to look further into this difference between both microbial collections and discovered that bacterial dispersal – the microbes’ ability to spread from one person to another within a community – appears to be the dominant process shaping gut bacteria composition among Papua New Guineans, while this was not the case among Americans.

The authors consider it likely that in less-industrialised countries like Papua New Guinea, the lack of sewage, waste paper or drinking water treatment may be the reason for increased bacterial diversity, whereas Western hygiene practices may be an important factor in microbiota alteration. Diet, experts indicate, is also likely to play a key role and one hypothesis suggests we may be missing some bacterial species due to our highly refined, low-fibre diet with a high proportion of protein in relation to carbohydrates.

As microbiota alterations among Western populations may be associated with the increase in some diseases like type 1 diabetes, obesity, allergies, Crohn’s disease, celiac disease, colitis or even colon cancer, the study’s findings are highly relevant due to the implications for human health. Possible outcomes include strategies to increase gut microbiota diversity and support the spread and transmission of beneficial but currently eradicated bacteria.

It’s not all bad news for Western guts, however. We may have less diversity because of our hygiene practices but we also have a lower incidence of gastrointestinal diseases that often affect communities in rural Papua New Guinea. The experts say additional research is required to determine the specific lifestyle and cultural factors involved in microbiota differences, each one’s importance and the mechanisms by which bacteria are altered. Knowing this would help to develop new ways to reduce the collateral damage of modern Western lifestyle without compromising the benefits for gut microbiota.