Here is an interesting, and really surprising, tidbit of research published in the journal, Nature Metabolism: it turns out there is a distinct bacterial microbiome signature associated with healthy aging, which, in turn, predicts survival in older people.[i] That’s not the surprising bit: you’ll need to read on for that!
A team of researchers analyzed data from over 9000 people, ranging in age from 18 to 101 years old, in 3 separate cohorts. They especially focused in on looking at the 900 or so people, 78-98 years old, who lived in community-dwelling for older individuals. What they discovered is that as we age, starting in mid to late adulthood, our bacterial microbiota should become increasingly unique and individualized. There is a steady decline in the amounts of core bacterial species including Bacteroides.
While the bacterial signature is unique, however, the metabolic functions performed by the bacteria are similar. There are amino acid derivatives found in the blood of older adults which are products of the gut bacteria. For example, tryptophan-derived indole, which in mice, extends life. Phenylacetylglutamine, which was highly associated with certain unique bacterial profiles, has been found at elevated levels in people 100 years of age or older. The lead researcher of the paper says, “This uniqueness signature can predict patient survival in the latest decades of life.”[ii]
This shift in the gut bacteria seems to start in mid-life, 40-50 years of age or so, and is associated with a clear metabolome profile, which is simply not seen in those who are not aging healthily. There is likely, of course, a two-way street meaning that an unhealthy microbiome leads to faster aging. Indoles, as mentioned above, are anti-inflammatory and thus, preventative of inflammaging.
The shocking part: what is pretty extraordinary is that this reduction of core species and shift toward an individualized profile is the marker for healthy aging: not maintaining the status quo, as you might think. What is healthy when you are young, it turns out, is not healthy when you are old. From the paper, “Retaining a high Bacteroides dominance into older age, or having a low gut microbiome uniqueness measure, predicts decreased survival in a 4-year follow-up. Our analysis identifies increasing compositional uniqueness of the gut microbiome as a component of healthy ageing, which is characterized by distinct microbial metabolic outputs in the blood.”
That’s just crazy, right?!
[i] Wilmanski, T., Diener, C., Rappaport, N. et al. Gut microbiome pattern reflects healthy ageing and predicts survival in humans. Nat Metab 3, 274–286 (2021). https://doi.org/10.1038/s42255-021-00348-0