Your microbiome ages as you do—and that’s a problem


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We’re all crawling with bugs. Our bodies are home to plenty of distinct ecosystems that are home to microbes, fungi, and other organisms. They are crucial to our well-being. Shifts in the microbiome have been linked to a whole host of diseases. Look after your bugs and they’ll look after you, the theory goes.

These ecosystems appear to change as we age—and these changes can potentially put us at increased risk of age-related diseases. So how can we best look after them as we get old? And could an A-grade ecosystem help fend off diseases and help us lead longer, healthier lives?

It’s a question I’ve been pondering this week, partly because I know a few people who have been put on antibiotics for winter infections. These drugs—lifesaving though they can be—can cause mass destruction of gut microbes, wiping out the good along with the bad. How might people who take them best restore a healthy ecosystem afterwards?

I also came across a recent study in which scientists looked at thousands of samples of people’s gut microbe populations to see how they change with age. The standard approach to working out what microbes are living in a person’s gut is to look at feces. The idea is that when we have a bowel movement, we shed plenty of gut bacteria. Scientists can find out which species and strains of bacteria are present to get an estimate of what’s in your intestines.

In this study, a team based at University College Cork in Ireland analyzed data that had already been collected from 21,000 samples of human feces. These had come from people all over the world, including Europe, North and South America, Asia, and Africa. Nineteen nationalities were represented. The samples were all from adults between 18 and 100. 

The authors of this study wanted to get a better handle on what makes for a “good” microbiome, especially as we get older. It has been difficult for microbiologists to work this out. We do know that some bacteria can produce compounds that are good for our guts. Some seem to aid digestion, for example, while others lower inflammation.
 
But when it comes to the ecosystem as a whole, things get more complicated. At the moment, the accepted wisdom is that variety seems to be a good thing—the more microbial diversity, the better. Some scientists believe that unique microbiomes also have benefits, and that a collection of microbes that differs from the norm can keep you healthy.
 
The team looked at how the microbiomes of younger people compared with those of older people, and how they appeared to change with age. The scientists also looked at how the microbial ecosystems varied with signs of unhealthy aging, such as cognitive decline, frailty, and inflammation.
 
They found that the microbiome does seem to change with age, and that, on the whole, the ecosystems in our guts do tend to become more unique—it looks as though we lose aspects of a general “core” microbiome and stray toward a more individual one.
 
But this isn’t necessarily a good thing. In fact, this uniqueness seems to be linked to unhealthy aging and the development of those age-related symptoms listed above, which we’d all rather stave off for as long as possible. And measuring diversity alone doesn’t tell us much about whether the bugs in our guts are helpful or not in this regard.
 
The findings back up what these researchers and others have seen before, challenging the notion that uniqueness is a good thing. Another team has come up with a good analogy, which is known as the Anna Karenina principle of the microbiome: “All happy microbiomes look alike; each unhappy microbiome is unhappy in its own way.”
 
Of course, the big question is: What can we do to maintain a happy microbiome? And will it actually help us stave off age-related diseases?
 
There’s plenty of evidence to suggest that, on the whole, a diet with plenty of fruit, vegetables, and fiber is good for the gut. A couple of years ago, researchers found that after 12 months on a Mediterranean diet—one rich in olive oil, nuts, legumes, and fish, as well as fruit and veg—older people saw changes in their microbiomes that might benefit their health. These changes have been linked to a lowered risk of developing frailty and cognitive decline.
 
But at the individual level, we can’t really be sure of the impact that changes to our diets will have. Probiotics are a good example; you can chug down millions of microbes, but that doesn’t mean that they’ll survive the journey to your gut. Even if they do get there, we don’t know if they’ll be able to form niches in the existing ecosystem, or if they might cause some kind of unwelcome disruption. Some microbial ecosystems might respond really well to fermented foods like sauerkraut and kimchi, while others might not.
 
I personally love kimchi and sauerkraut. If they do turn out to support my microbiome in a way that protects me against age-related diseases, then that’s just the icing on the less-microbiome-friendly cake.

To read more, check out these stories from the Tech Review archive:
 
At-home microbiome tests can tell you which bugs are in your poo, but not much more than that, as Emily Mullin found.
 
Industrial-scale fermentation is one of the technologies transforming the way we produce and prepare our food, according to these experts.
 
Can restricting your calorie intake help you live longer? It seems to work for monkeys, as Katherine Bourzac wrote in 2009. 
 
Adam Piore bravely tried caloric restriction himself to find out if it might help people, too. Teaser: even if you live longer on the diet, you will be miserable doing so. 

From around the web:

Would you pay $15,000 to save your cat’s life? More people are turning to expensive surgery to extend the lives of their pets. (The Atlantic)
 
The World Health Organization will now start using the term “mpox” in place of “monkeypox,” which will be phased out over the next year. (WHO)
 
After three years in prison, He Jiankui—the scientist behind the infamous “CRISPR babies”—is attempting a comeback. (STAT)
 
Tech that allows scientists to listen in on the natural world is revealing some truly amazing discoveries. Who knew that Amazonian sea turtles make more than 200 distinct sounds? And that they start making sounds before they even hatch? (The Guardian)
 
These recordings provide plenty of inspiration for musicians. Whale song is particularly popular. (The New Yorker)
 
Scientists are using tiny worms to diagnose pancreatic cancer. The test, launched in Japan, could be available in the US next year. (Reuters)



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