The research, published in Science, found that intake of meat, fat, carbohydrates, and alcohol appear to influence the type of bacteria thrive in the gut. However, the study also suggests that dietary changes may not mean we can quickly replace one microbial population with another.
“We used diet inventories and 16S rDNA sequencing to characterize fecal samples from 98 individuals,” wrote the researchers, lead by Frederic Bushman from the University of Pennsylvania.
“Fecal communities clustered into enterotypes distinguished primarily by levels of Bacteroides and Prevotella … Enterotypes were strongly associated with long-term diets, particularly protein and animal fat (Bacteroides) versus carbohydrates (Prevotella),” they added.
Much research has focused on the bacterial populations living in the gut – often referred to as the microbiome.
Studies have suggested that these microbes play a role in health and disease, and could have implications for conditions including obesity and inflammatory bowel disease. Recent research in mice also suggested that intestinal bacteria may even effect mood and depression.
"We're all wrestling with the questions of what bugs are there and what they are doing," said Bushman.
Earlier this year a large research project published in Nature brought some order to the chaos, reporting that human populations can be divided into three ‘enterotypes’ depending on the species – or ecosystem – of bacteria dominating their gut: Bacteroides, Ruminococcus, or Prevotella.
Professor Jeroen Raes, who led the Nature paper, recently told NutraIngredients that he believes the discovery of the different enterotypes is only the beginning; noting their initial study was not large enough to define any of the functionalities of the different types.
Bushman and his colleagues asked 98 healthy volunteers to fill in two questionnaires, one asking about what they ate and drank recently, the other about their long-term dietary habits. The team then took stool samples from the subjects and analyzed their DNA content to determine the makeup of the gut flora.
They found similar clustering into enterotypes – though only two of the three showed up clearly – and discovered a link between dietary habits and enterotypes.
Bushman and his team reported that people who eat a lot of meat and saturated fat tended to have more Bacteroides in their flora; Ruminococcus prevailed in people who consumed lots of alcohol and polyunsaturated fats, whereas Prevotella favoured a diet rich in carbohydrates.
The team then sequestered ten volunteers; feeding half of them a fixed diet very high in fat and low in fibre and the other half of the subjects had the opposite menu.
The researchers found that the bacterial populations began to shift within both groups, with some species becoming more common and others less common, but people had the same enterotype when the study ended after 10 days.
If switching gut enterotype is possible, the team concludes, it may take a long-term dietary intervention.
Published online ahead of print, doi: 10.1126/science.1208344
“Linking Long-Term Dietary Patterns with Gut Microbial Enterotypes”
Authors: G.D. Wu, J. Chen, C. Hoffmann, K. Bittinger, Y.Y Chen, et al