Updated 18th March 2024

Why is the gut microbiome important for healthy aging?

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Your gut is home to trillions of microbes that make up your gut microbiome. These bugs are central players in your health throughout your life. But research now also paints a picture of your gut microbes paving the way for good health in old age.

Life expectancy has increased across many regions of the world in the last few decades. On the whole, we are living longer than our parents’ and grandparents’ generations. 

But with a longer life comes an increased risk of chronic health conditions. 

In the U.S., 85.6% of people aged 65 and over live with at least one chronic condition like type 2 diabetes, heart disease, COPD, asthma, cancer, or arthritis. And nearly 25% of people in this age group are living with at least three of these conditions. 

What is the secret to healthy aging? Experts are increasingly pointing to our gut microbiome as one of the key factors to help us live longer and healthier lives.

As ZOE’s co-founder Prof. Tim Spector, a world-leading scientist and microbiome expert from King’s College London, puts it: 

“The gut microbiome holds the key to healthy aging, both as an indicator of health and by its influence on the immune system and the body’s natural repair mechanisms.” 

ZOE runs the largest study of nutrition and the gut microbiome in the world, with over 15,000 participants so far. With the ZOE program, you receive personalized nutrition advice, based on the latest cutting-edge science, to support your metabolic health at your current life stage.

You can take our free quiz to find out more. 

What is the gut microbiome?

Inside your gastrointestinal tract are trillions of bacteria, viruses, and other microbes. Together, these microbes in your gut are called your gut microbiome

Our research has shown that everyone’s gut microbiome is different, even that of identical twins. You may share 99% of your DNA with your fellow humans, but the specific makeup of the different species of microbes in your gut is entirely unique to you.

For example, 99.7% of our study participants have a bacterium called Faecalibacterium prausnitzii in their intestines, but only around one-third have a newly discovered microbe called Firmicutes bacterium CAG:170

It’s the combination and individual genetic variants of these many different microbes that is unique to each of us.

But what do the microbes in your gut do? They are instrumental in keeping your immune system functioning, they likely impact your mental health, they help digest what you eat, and they influence how your body responds to food.  

You get your first dose of microbes during birth, or possibly even before. It then takes until around the age of 3 until your gut microbiome is fully established.

Throughout your life, your gut microbiome can change. And your diet influences these changes, along with where you live and the medications that you take, particularly antibiotics. 

But there is also a new body of research showing that your gut microbiome changes as you age. And this has implications for your health. 

What happens to your gut microbiome as you age?

One study that involved over 9,000 people between the ages of 18 and 101 found that your microbial uniqueness seems to come with another perk. 

The authors found that participants’ gut microbiomes diverged from consistent patterns and became increasingly individual in mid to late adulthood. 

Those aged 80 and over whose gut microbiome had become more unique were, on the whole, healthier. This group also had fewer Bacteroides than their peers who were less healthy. This was independent of any medications used.

A drop in the diversity of the microbes in the gut has also been linked to increased frailty during aging.

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Another study looked specifically at the microbes in the small intestine of 251 people aged 18–80.

The researchers found more bugs from the Proteobacteria group, particularly Escherichia, Lactobacillus, and Enterococcus in older individuals. 

They also saw increases in the levels of Klebsiella in line with how much medication a participant took, and in the levels of Clostridium in participants with chronic health conditions. 

But are the microbiome changes merely a by-product of the aging process, or do they drive our health as we get older? 

Gut ‘absolutely critical to healthy aging’

Recent research may hold clues to the answer. Giving older mice gut microbiome samples from younger ones improved the older mice’s gut immune system

In another study, older mice saw improvements in their brain function and immune system when they received gut microbiome samples from young mice.

And a recent study found that centenarians living in Japan had a set of bacteria that can produce particular bile acids. 

These might have antimicrobial effects, the study author suggests, providing protection from infection by multidrug-resistant pathogens like C. difficile and E. faecium

It’s clear that the evidence increasingly points to our gut microbiome as something we should pay closer attention to as we age. 

“I believe the gut is absolutely critical to healthy aging,” gastroenterologist, New York Times best-selling author of Fiber Fueled, and ZOE’s U.S. Medical Director Dr. Will Bulsiewicz explained.  

“Research suggests that our gut microbiome changes as the years go by. But here's the good news. We have the ability to shape our microbiome through our diet and lifestyle choices.” — Dr. Will Bulsiewicz

So, what are these foods and lifestyle changes that will keep your beneficial and unique gut bacteria happy while you age? 

Nutrition tips for gut health and aging

The food you eat shapes the landscape of the microbes that inhabit your gut, and changing your diet can alter this significantly and rapidly. 

Microbes love fiber, a type of carbohydrate that humans can’t digest. What was once seen as indigestible “bulk” is now viewed as the prime food of choice for your beneficial gut bacteria. 

“Given one choice, the most important factor from my perspective would be to maintain a diet that contains a wide diversity of fiber-rich plant foods,” Dr. Bulsiewicz explained.  

He pointed to research that highlights the lack of sufficient fiber in our diets. Among adults aged 71 and over, “only 7% of men and 16% of women aged 71 and older are consuming the minimum recommended amount of daily fiber.”  

“If we fix this fiber deficiency on an individual basis and ensure that everyone is consuming an adequate amount of daily fiber, we will surely be taking a huge step toward healthy aging and a healthier gut microbiome.” — Dr. Will Bulsiewicz

There are plenty of ways to increase your fiber intake and feed your gut bacteria. 

Make the fruit and vegetable section your first stop at the grocery store. The plants that you find here (and their frozen and canned counterparts) are brimming with nutrients and fiber. 

Your gut microbes will be happy, and all that fiber will also help keep you regular and avoid constipation. 

Great sources of fiber include:

  • fruit like apples, oranges, raspberries, blueberries, strawberries, peaches

  • vegetables like Brussels sprouts, spinach, kale, avocado, broccoli, zucchini, cauliflower, and bell peppers

There are plenty of other plants that are high in fiber, such as whole grains, nuts and seeds, and legumes. 

Plants, polyphenols, and fermented foods

Prof. Spector recommends eating 30 different plant foods each week. 

But as you age, you may find it harder to incorporate all that fiber in your diet, Dr. Bulsiewicz noted. 

“Dental issues, decreased saliva, changes in dietary preferences are all factors that can contribute to struggles with fiber as we age and may explain part of the changes that we see in the gut microbiome,” he said. 

“This is a vicious cycle that feeds into itself, but we can break the cycle by placing an emphasis on getting fiber-rich plant foods into our diet in a way that is more palatable, such as in a smoothie, oatmeal, or as a part of a soup or stew,” Dr. Bulsiewicz continued. 

You can check out our 10 tips for increasing your plant intake.

Fruit and veg that come in bright colors also contain a type of antioxidant called polyphenol, as do tea, coffee, red wine, and dark chocolate. 

Prof. Spector described polyphenols in red wine as “rocket fuel for your microbes” in a recent podcast. Research also shows that polyphenols may keep chronic conditions at bay

Aside from fiber and polyphenol-rich foods, he also recommends fermented foods, which are full of probiotic, or “friendly,” bacteria. 

To get your regular probiotic boost, you can eat:

  • unsweetened live yogurt

  • aged cheeses like cheddar, parmesan, and Swiss cheeses 

  • sauerkraut

  • kimchi

  • kefir

  • kombucha

"The key is to include a small shot of fermented foods daily, rather than consuming a large amount of fermented food once in a while,” Prof. Spector advises. 

Other ways to support your gut microbiome as you age

The food you eat has a direct impact on your gut microbiome. But there are other factors, too. 

Exercise is great for your health, but your gut bugs are also big fans of physical activity, research suggests. Even low-intensity exercise can make a difference. So, pick your favorite ways to be active, whether it’s walking, gardening, dancing, or working out in the gym. 

Sleep is another important factor in your gut health as you age, Dr. Bulsiewicz notes. Poor sleep can negatively affect your gut microbiome, which, in turn, can make it harder to get good quality sleep. 

Prioritize your sleep to break this vicious cycle and focus on eating those gut-friendly foods to ensure that your gut microbes don’t keep you up at night. 

As Dr. Bulsiewicz concludes: “Maintaining a high fiber diet, consuming fermented foods, staying physically active, and making sure to get adequate, restful sleep are strategies we can apply to our daily lives to help support a healthy gut microbiome as we age.” 

The ZOE at-home test uses the latest scientific advances to analyze your gut microbiome, along with your blood sugar and blood fat responses, to help you find the best foods for your gut microbiome and your long-term health goals.  

Take our free quiz to join thousands of other customers who are already part of ZOE’s personalized nutrition program. 


Age and the aging process significantly alter the small bowel microbiome. Cell Reports. (2021). https://www.cell.com/cell-reports/fulltext/S2211-1247(21)01219-5 

Development of the gut microbiota in infancy and its impact on health in later life. Allergology International. (2017). https://www.sciencedirect.com/science/article/pii/S1323893017301119

Exercise modifies the gut microbiota with positive health effects. Oxidative Medicine and Cellular Longevity. (2017). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5357536/

Gut microbiome pattern reflects healthy ageing and predicts survival in humans. Nature Metabolism. (2021). https://www.nature.com/articles/s42255-021-00348-0 

Heterochronic faecal transplantation boosts gut germinal centres in aged mice. Nature Communications. (2019). https://www.nature.com/articles/s41467-019-10430-7

Microbiota from young mice counteracts selective age-associated behavioral deficits. Nature Aging. (2021). https://www.nature.com/articles/s43587-021-00093-9

Novel bile acid biosynthetic pathways are enriched in the microbiome of centenarians. Nature. (2021). https://www.nature.com/articles/s41586-021-03832-5

Role of the gut microbiota in nutrition and health. The BMJ. (2018). https://www.bmj.com/content/361/bmj.k2179 

The effects of polyphenols and other bioactives on human health. Food & Function. (2019). https://pubs.rsc.org/en/content/articlelanding/2019/FO/C8FO01997E

Usual nutrient intake from food and beverages, by gender and age, what we eat in America, NHANES 2015-2018. (2021). https://www.ars.usda.gov/ARSUserFiles/80400530/pdf/usual/Usual_Intake_gender_WWEIA_2015_2018.pdf

Signatures of early frailty in the gut microbiota. Genome Medicine. (2016). https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4731918/

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