Bacteria in guts of elderly differ from those of the young

Los Angeles Times

We are teeming with microscopic life. Scientists recently reported on the billions of bacteria and fungi that grow inside us, finding a lot of diversity from person to person — and from spot to spot on the human body.

Those findings were in 242 young adults (ages 18 to 40) in exceptionally good health. Even gum disease was grounds for exclusion, as we noted in a news article at the time.

But what about older people?

It’s known that their bacterial populations are less stable than those of younger people and that the gut flora of one elderly individual can differ greatly from that of another.


It’s also known that the populations of bacteria growing inside them are less diverse than what’s seen in younger people. These changes are believed linked to events that take place as we grow older, such as a lengthening of the time it takes food to pass through our guts, reduced saliva production and others.

Now a new paper published in Nature offers a more detailed look at the gut flora of those 64 and older.

The research, by Paul W. O’Toole of University College Cork in Ireland and colleagues, analyzed stool samples from 178 elderly people living in a variety of settings: at home, in long-term residential care and shorter-term rehabilitation, as well as those who attended day hospitals.

The scientists were particularly interested in learning if diet was linked to the structure of the gut flora and maybe to disease and frailty. So they obtained detailed dietary information from the study subjects, as well as data linked to their physical and psychological health and the status of their immune system.

None of the subjects (ages 64 to 102, with an average age of 78) had been recently treated with antibiotics.

They found (among other things):

--Bacterial composition depended on where people lived. Those in long-term care had more bacteria from a large group called Bacteroides than did the others, who had more of another group, Firmicutes.

--People in long-term care also had a less diverse bacterial population.

--The longer people were in long-term care, the more different their bacterial populations looked from others not in long-term care.

--Diet composition influenced the microbe communities: People with a healthful, diverse diet had a more diverse bacterial community. Those whose diet was low in fat and high in fiber had more diverse bacteria than those whose diets were low in fiber and either low or high in fat.

--People in long-term care tended to have low-fiber diets.

--People in long-term care had lower stool levels of the chemical butyrate, among others, created presumably by gut bacteria. Levels of such substances can affect health.

--People in long-stay and rehab facilities had more chemical signs of gut inflammation.

--Certain patterns of microbes were linked to frailty and poor health, even when the scientists made statistical adjustments for where the subjects were living.

All in all, these and other findings in the paper (and in others) point toward an influence of microbial flora on health as we age, the authors write. Or, as they put it, “The clear association between diet and microbiota outlined in this and previous studies argue in favor of an approach of modulating the microbiota with dietary interventions designed to promote healthier aging.”

Specifically, they suggest dietary supplements that are carefully designed to improve microbial health.