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People and Their Gut Microbes Are Life-long Partners

Scientists have found that the types of bacteria in our gut change very little throughout our lives. The human microbiome, or the collection of microbes present in the body, includes trillions of bacteria living in our gastrointestinal tract. There is evidence that the composition of the gut microbiome can affect human health. One common approach to study the gut microbiome is to sequence the DNA of the bacteria living there, but this method has been limited by the sensitivity and accuracy of the DNA sequencing technique, which had difficulty discerning between individual types or strains of bacteria and errors in the sequencing process. To overcome this limitation, a group of researchers developed a new way to sequence the DNA of gut bacteria that improves the accuracy to a point where the scientists can differentiate between individual bacterial strains. Using this method to sequence DNA contained in stool samples from healthy adults over time, the scientists found that the relative amount of each bacterial strain changes very little over several years. In other words, the demographics of the gut microbial community are likely stable in healthy individuals for decades or longer. The researchers also compared the microbial communities of family members and found them to be much more similar than the microbiota of unrelated people. This finding suggests that family members are colonized by similar bacteria through exposure to a shared environment and that the gut microbiome is established relatively early in a person’s life—probably within a few years after birth.

The researchers did find one situation that will disrupt the stability of the microbiome, however: when someone undergoes a drastic change in diet that causes substantial weight loss. A group of volunteers consumed a calorie-restricted liquid diet for several months and subsequently lost about 10 percent of their body weight. The stability of the gut microbiome quickly broke down under these conditions, and the individuals whose weight fluctuated the most also had the least stable microbiomes. Overall, these studies suggest that the types of bacteria in the gut microbiome will remain relatively constant throughout a person’s life, though this stability is affected by changes in diet and weight.

This points to the gut microbiome as a potential predictor of an individual’s state of health, such that changes in the microbiome could be used in the future as markers for overall well-being and disease development.