The microbiome of bacteria living in the human gut has a profound impact on health. However, this aspect of health that still confuses scientists. In most adults, bacteria outnumber human cells. But, the type and amount of bacteria in a single person, the bacteria’s variability from person to person and the microbiome’s role in health, is not well understood. Your health influences your microbiome, but your microbiome affects your health in return. For year scientists have been fascinated by researching the bacteria inside of us, trying to learn about the complex relationship we have with our internal partners. Studies have shown that our bodies hold anywhere from 300 to 500 strains of bacteria with nearly 2,000,000 genes. Because of the importance of a person’s microbiome, scientists are eager to learn more and several studies published recently might be significant steps forward.

We are born without much of a microbiome at all. It has to grow and develop as a child encounters the world. Research published late last year showed there were distinct phases of gut development in early life. The researchers focused on seeking the triggers for type 1 diabetes in children with genetic markers for the disease. Studying stool samples from kids, researchers showed just how much and how quickly the body’s microbiome develops. However, scientists aren’t sure when changes to the microbiome slow down.

A study from earlier this year may hold a lot of answers. The giant study used artificial intelligence to examine more than 3,600 samples of bacteria from the guts of 1,165 healthy people in different locations on Earth. Participants were between the ages of 20 and 90. By feeding the information into an algorithm, researchers would predict the age of the participant to within four years. This shows that, while our bacterial makeup may be very different, there are strong similarities in how our microbiomes age. Prior to this study, scientists weren’t sure if adult microbiomes changed at all or if they were stable throughout life. The research has yet to be peer-reviewed and needs to dive deeper. Though we know that our microbiomes hold hundreds upon hundreds of different strains, the algorithm was only focused on 95 species. The researchers themselves wondered if they were seeing the results of bacteria changing due to aging or if, perhaps, they were looking at history — seeing common lifestyle markers and fad dieting impacts from decades past. Which vegetables are in fashion or how society views fat or carbs has a big impact on our bodies. Out of the 95 strains of bacteria, 39 were the strongest predictor of age, and the scientists are looking into them more thoroughly. Better understanding of physical age would be a groundbreaking achievement as it would allow doctors to tailor personalized medical treatment on a case-by-case basis.

Now, findings published this month suggest that, by altering people’s microbiome, we could promote healthy aging. Immunologists working with mice at the Babraham Institute saw that, when an older mouse received a fecal transplant from a younger mouse, it aided their immune system. The older mice regained such good immune response that Dr. Michelle Linterman said their “immune responses… were almost indistinguishable from those of the younger mice.” Considering the huge role the immune system has, this might be a giant leap forward.

Healthy aging would allow everyone to enjoy more fun quality time with our friends and family. Moreover, the broader implication suggests that probiotics and diet may, in and of themselves, be able to aid healthy aging more than we realized!