The good news is that it isn't all downhill when you hit 30 – in fact, the researchers found no significant increase in the ratio of harmful to beneficial bacteria as we age. Instead, the increase of bacteria that may promote the detrimental effects of aging is balanced out by a decrease in harmful bacteria, related to an increase in "memories" that help us fight off pathogens we have already been exposed to.
The study authors are careful to point out that any differences in gut microbiota between the elderly and the young cannot simply be put down to the process of aging. Diets and lifestyle have changed significantly over the last 100 years and so differences may be more reflective of that rather than anything else.
"In other words, any features identified today as associated with the youth may become the signature of the elderly in 50 years, provided global diet and lifestyle keeps changing," the study authors explain.
"Depending on the extent of such microbiological 'generation gap,' any future intestinal aging clock may need to be regularly updated to account for an ever-changing environmental context."
Again, this study has yet to be peer-reviewed so we'll have to wait to see if these results are confirmed.