Nature vs nurture: Study finds consistent gut microbiome differences among ethnicities

Nearly 1,700 Americans of different genders, ages, weights and ethnicities were sampled in the study published in the journal PLOS Biology,​ which concludes that changing the gut microbiome holds great potential to beat illness.

The goal of the study was to evaluate, for the first time, if there were reproducible differences in gut microbiota across ethnicities within an overlapping US population, as ethnicity is one of the key defining factors for health disparity incidence in the US.

The findings demonstrate that ethnicity consistently captures gut microbiota with a slightly stronger effect than other variables, ethnicity is moderately predictable from total gut microbiota differences; and 12 taxa recurrently vary in abundance between the ethnicities, of which the majority have been previously shown to be heritable and associated with human genetic variation. 

The Vanderbilt University team discovered 12 particular microbial taxa that regularly vary in abundance by ethnicity.

The 12 bacteria featured in this research were: Christensenellaceae, Clostridiales, Coriobacteriaceae, Dehalobacteriaceae, Odoribacter, Odoribacteriaceae, Peptococcaceae, RF39, Rikenellaceae, Veillonella, Verrucomicrobiaceae and Victivallaceae

The research report points out that ethnicity captures many factors, ranging from diet to genetics, making it difficult to say exactly why microbiomes change in the way they do.

But this discovery is a baseline for understanding healthy microbiome differences among individuals. It also holds promise in the burgeoning field of personalisation, because it is far easier to change a person's microbiome than their genes, the research report states.

The report states: “Many chronic diseases disproportionately affect ethnic minorities, with underlying causes of that difference unexplained. Perhaps some answers could lie in the gut microbiome.”​

Potential for beating illness​

Researcher Seth Bordenstein, professor of biological sciences, said changing the gut microbiome to beat illness really does hold great potential.

For instance, the family Odoribacteriaceae and genus Odoribacter​ are primary butyrate producers in the gut, and they have been negatively associated to severe forms of Crohns disease and Ulcerative Colitis. The study shows that Asian-Pacific Islanders possess significantly less Odoribacteriaceae and Odoribacter​ than Hispanics and Caucasians in both data sets and severity of Ulcerative Colitis upon hospital admission has been shown to be significantly higher in Asian Americans.

"Human genomes are 99.9 percent the same between any two people, so what we're really interested in is what explains the marked variations in gut microbiomes between people,"​ said Bordenstein.

"What are the rules, and can we manipulate that microbiome in order to improve health and medicine in the long run? If you look at common factors associated with gut microbiome differences, such as gender, weight or age, you find many inconsistencies in the types of gut bacteria present. But when we compare differences by patients' self-declared ethnicities, we find stable and consistent features of bacteria present in the gut.​

"You may buy probiotics over the counter at a drugstore, but those are unlikely to affect your microbiome in a substantial way​.

"They often are at too low a dose, and they may not even be viable bacteria. Moreover, one size may not fit all. But with more of this kind of research, we can hone in on the relevant differences and doses of bacteria that may reverse illness or prevent it from developing in the first place."​

Historical research​

While ethnic diversity is generally under-represented in current microbiota studies, evidence supporting an ethnic influence on microbiota composition among first generation immigrants has been recently demonstrated in a Dutch population in a study published in Nature Medicine​ called “Depicting the composition of gut microbiota in a population with varied ethnic origins but shared geography”.​

Another recent study​ on how the microbiome changes when immigrants move countries.

showed the change in gut microbiome diversity could explain the rising rates of obesity amongst immigrants when their diet is modified.

The study published in the journal Cell ​found that immigrants and refugees moving from Southeast Asia to the US demonstrate a ‘westernisation’ of their gut microbiota.

In particular, new arrivals appear to lose the bacterial enzymes associated with plant fibre degradation.

Source: PLOS Biology​​​

“Gut microbiota diversity across ethnicities in the United States”​​

Published online ​December 4, 2018. DOI: 10.1371/journal.pbio.2006842​

Authors: Andrew W. Brooks et al