“What is clear cut is that the gut microbiome plays a role in many diseases,” Jens Walter, PhD, of the University of Alberta, told NutraIngredients-USA. “We have information on this mainly due to animal research. The gut microbiome has a role in diseases like obesity or metabolic disease.”
The gut as ecological system
Walter is an expert on the ecological aspects of the gut microbiome. In other words, he studies that community as another researcher might look at the populations of microorganisms in a pond. Work along this line, some of which was detailed at the recent Probiota Americas event in San Diego hosted by NutraIngredients-USA, has turned up some striking differences among the kind of bacteria various human populations carry around within themselves. In San Diego, researchers talked about the gut populations of the Hazda in Tanzania and Yanomami tribe in Venezuela.
Walter’s own recently published work, which came up with results similar to those earlier studies, compared the fecal bacteria of two non industrialized populations of Papua New Guineans with that of US residents. “Papua New Guineans harbor communities with greater bacterial diversity, lower inter-individual variation, vastly different abundance profiles, and bacterial lineages undetectable in US residents,” Walter and his coauthors wrote.
Too clean in the West?
Western guts looks very different from those of the Papuans, and they looked more different from each other, too. Interestingly, while Walter and his collaborators said “the exact consequences on metacommunity characteristics are insufficiently understood, and the underlying ecological mechanisms have not been elucidated,” they were able to hypothesize a reason for these differences. Walter said there are four processes that govern microbial community assembly: selection, drift, dispersal and diversification.
“If you apply that to the human microbiome it makes a lot of sense,” he said. “It’s not only that our microbiome is a lot less diverse, but it is a lot more individualized. We think dispersal limitation in the West is one of the limiting factors. The dispersal of the microbiome is very much inhibited because of sanitary conditions in the West. Caesarean section is one mechanism by which we prevent dispersal. I’m not sure how important that is overall, but it certainly is important early on.”
While the poor sanitary conditions and lack of modern medical care mean that these indigenous populations suffer infectious disease at greater rates than do Westerners, they don’t suffer from chronic health conditions that are endemic in the West, such as obesity and cardiovascular disease. But it’s not at all clear whether the differences in the gut microbiome are the cause of this, or are a result of other lifestyle differences.
“We do have something of a chicken and egg question here. The important thing that is lacking is that we don’t understand what features of the gut microbiome contribute to disease in humans,” Walter said.
The way forward
Walter said continued work to shed light on the microbial community characteristics of the human gut will eventually lead to a better understand of how this system really impacts the overall health of the human organism. Bioinformational statistical modeling techniques can help here, as the research generates mountains of data that otherwise be daunting or well nigh impossible to analyze. Complicating this effort is the frequent discovery of new species inhabiting the human gut.
“We are definitely not leading in this area. We do use these techniques, and I like where the field is going,” he said.
In the meantime, researchers and product developers are left with something of a hunt and peck approach to trying to positively affect gut health.
“We have sequenced the gut microbiome in healthy individuals and have compared it to those in diseased individuals. We have identified ‘dysbiotic’ patterns in many of these diseases, such as inflammatory bowel syndrome. But we don’t really know which patterns contribute to disease,” he said.
“We are starting to have a reasonably good idea of what we don’t want to see. But in a healthy group of people, I wouldn’t know how to make their gut microbiomes ‘healthier’ other than feeding them more fiber. As far as I know, no probiotic on the market has been designed specifically to target these dysbiotic patterns,” Walter said.