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Western guts have lower bacterial diversity

Gut microbiome Our western lifestyle, hygiene and diet may reduce the diversity of important gut bacteria, a new study shows.

Scientists analysed the faecal bacteria of people living in the United States and rural Papua New Guinea, and found that Papua New Guineans had a greater number of different gut bacterial species.

The study, published today in Cell Reports , shows while both groups still had many important gut bacteria species in common, the US residents were missing around 50 bacterial types that were dominant in the rural Papua New Guineans.

There has been growing interest in recent years about the impact of gut bacterial populations -- known as the gut microbiome -- on health.

Research is suggesting that changes observed in the gut microbiome of western populations may be contributing to the rise in diseases such as type 1 diabetes, rheumatoid arthritis, obesity, allergies, and colon cancer.

Co-author Dr Andrew Greenhill, senior lecturer in microbiology at Federation University, says the study showed most of the lost diversity was in the bacterial 'fringe dwellers'.

"These make up somewhere between 5-10 per cent of the total number of bacteria in the gut," says Greenhill.

"Perhaps the [loss of] the organisms that lead to increased diversity in traditional lifestyles, may have some health impact."

While the spread of bacteria from person to person -- aided by a lack of sewage, waste water or drinking water treatment -- is likely the main reason for the greater bacterial diversity in the Papua New Guinean residents, diet also plays a role in altering our gut microbiome.

"Other studies show that if you introduce whole grains back into the diet of western people, you see an increase in the diversification of their gut microbiota," Greenhill says.

Greenhill says the high proportion of protein relative to carbohydrates, in the western diet also probably has an impact on the composition of the gut community structure.

Similarly, increased rates of caesarean sections may also be impacting.

"It's no accident, and is probably better design than what it initially looks, that the birth canal is so close to the end of the gastrointestinal tract," Greenhill says.

Balancing act

But it's not all bad news for the Western gut. While we may have less biodiversity, improved hygiene practices mean we also have a lower incidence of the sort of gastrointestinal infectious diseases that regularly sweep through low-income communities such as those in rural Papua New Guinea.

"We're not saying that we should throw away our toilets and stop washing our hands," Greenhill says.

What is required is more research on how these bacterial species affect health, and how this can be used to benefit populations in non-industrialised and industrialised nations, he says.

"If there's evidence that they are actually contributing to lifestyle diseases, it would come to finding ways of getting them back into the industrialised gut microbiota, but without reducing the benefits that have come from reduced dispersal [which] is primarily due to improved sanitation and hygiene."

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