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There's no magic elixir for healthy aging, but here's one more thing to add to the list: good gut health.
A study published in the latest issue of Nature finds diet may be key to promoting diverse communities of beneficial bacteria in the guts of older people.
To evaluate this, researchers analyzed the microbiota, or gut bacteria, of 178 older folks, mostly in their 70s and 80s.
Some of the people were living in their own homes, and their diets were rich in fiber, fruits, vegetables, grains, poultry and fish.
Others were living in long-term care facilities or nursing homes where the typical diet was much less varied. "Mashed potato and porridge were the only staples in this diet type that were consumed daily," explains Paul O'Toole of the Alimentary Pharmabiotic Centre at University College Cork in Ireland. Meals were supplemented with puddings, cookies and sugar-sweetened beverages such as tea.
O'Toole's team found that people living independently, who had the most diverse diets, also had more varied gut bacteria. And they also scored better on clinical tests measuring frailty and cognitive function. In other words, "they were healthier older people," says O'Toole.
There may be many factors at play here, but O'Toole thinks diet is key. "We were surprised that the correlations between microbiota and health came out so strongly," O'Toole says.
There's an explosion of research into the gut microbiome as scientists fine-tune methods to analyze bacteria in the gut, and with that comes an emerging body of evidence that diversity of gut bacteria is important.
"What we're only now beginning to realize is that there's very close interaction between the bacteria within GI tract and human health and disease," says Ilseung Cho, a gastroenterologist at NYU School of Medicine.
Beneficial bacteria do a lot for us, says Cho. They help with digestion, help our bodies make vitamins, and also likely help support a strong immune system.
But they also have to compete with the harmful bacteria. That's why we want a variety of the good kind in our guts.
"If you have a lot of diversity and one bacteria that's doing something good is knocked out," explains Cho, "then you may have other bacteria that can compensate for that loss."
These new findings are not proof that diverse microbiota lead to better health. But experts say this paper is important because it establishes a link.
"Is it really that diet is altering the health of individuals through altering the gut microbiota?" asks Gary Wu of the University of Pennsylvania. "Or is it that people who are not as well tend to be housed in long-term care facilities?" It's possible that the lack of bacterial diversity isn't the cause of illness, but a sign of sickness.
Wu says it will take additional studies to unravel cause and effect. Nonetheless, he says, this new Nature paper is intriguing.
"I think there's growing evidence that diet is very important in regulating the composition of the gut microbes," says Wu.