When she died in 2024, Spain's Maria Branyas was the world's oldest woman. She was 117.
Experts believe the secret to her longevity may have been the bacteria living in her gut – her microbiome – and luckily, before she died, she donated stool samples to medical scientists so they could learn more about it.
The international team of researchers studying the samples were stunned to find that, along with her advantageous genetic profile, her gut was flourishing with the associated microbial community of youth.
There was plenty of Bifidobacterium, which typically gets star billing in probiotic supplements due to its inflammation-reducing properties, not to mention its ability to boost our immune systems. It also aids in digestion and helps produce essential micronutrients like vitamins.
Branyas may be the most extreme example, but record numbers of people are now living past their 100th birthday.
Yet as more of us live longer, more of us are having to live with chronic disease, so the goal of longevity researchers is to work out how to stretch our healthspan – the illness-free years of our lives.
Gut health is a promising target for achieving this. While we’re largely stuck with our genes, our unique microbiomes can be influenced by diet and lifestyle.
As scientists learn more about what keeps the gut microbiomes of the longest-lived people so youthful, the better our chances are that more of us can follow in their footsteps…
An even mix of gut bacteria could be better than a richer mix
The diversity of bacteria in our guts has been used as a measure of overall health, albeit a crude one, for years now. But recent studies suggest that what sets the guts of centenarians apart isn’t so much the variety of species living in them, as the balanced spread of those species.
A 2023 study examined the guts of over 1,500 people, including 297 centenarians.
Dr Shuai Wang at China’s Guangxi Academy of Sciences says that while this study’s findings “support the idea that centenarians possess distinct microbiome signatures linked to their longevity,” it ultimately showed that rather than diversity, their good health was “better reflected by evenness.”
In fact, says Wang, “in many diseases, gut microbiota diversity can be greater in sick patients compared to healthy individuals.
This increase often occurs due to a loss of gut barrier resistance, allowing for the colonisation of rare microbes or microbes that typically inhabit other areas.”
In older adults, he says, “a decline in gut barrier function can lead to a proliferation of rare microbes, which may result in higher perceived richness” but not necessarily translate to any additional physical or mental health benefits.
The key to reinforcing a declining gut barrier is fibre. Eating a high-fibre diet with plenty of vegetables keeps those barriers strong, and so does avoiding alcohol.
Dr Mary Ni Lochlainn, a geriatrician at King’s College London, is another expert who thinks that diversity of gut bacteria isn’t everything.
She ran a trial supplementing older twins with prebiotic fibre (dietary fibre that supports the microbiome) and found that “they all had a decrease in diversity, because the prebiotic was preferentially causing more of certain microbes to grow,” she says.
“But they also all had improved cognition, so, it shows me the limitation of diversity.”
While diversity may not be the be-all and end-all of gut health, it can still play a positive role in later life. A 2016 study into frailty and the gut by Lochlainn’s colleagues at King’s found a correlation between frailty and lower bacterial diversity.
The bacteria that (we're pretty sure) help superagers thrive
Bifidobacterium, which was found to be so plentiful in Maria Branyas’s gut, produces short-chain fatty acids – a potential protective against frailty in old age. But other bacteria produce them too, including Faecalibacterium prausnitzii – commonly known as ‘F. Prau’.
Another finding from the KCL frailty study was that “the more F. Prau you had, the less likely you were to be frail,” says Lochlainn. “It’s something that healthier people seem to have, and lacking it is a bad thing.”
F. Prau plays an important role in processing the fibre that we eat into short-chain fatty acids like butyrate, which, Lochlainn says, “is associated with good health, immune function, various metabolic processes, muscle function and [more].”
F. Prau isn’t found in any specific foods, but eating plenty of fruit and veg will provide the bacteria with the fibre it needs to proliferate in your gut.
Wang’s study identified more short-chain-fatty-acid-making bugs in the guts of centenarians: Blautia, Lachnoclostridium and Phascolarctobacterium.
He says these are beneficial microorganisms recognised for their roles in reducing inflammation, alleviating obesity and minimising metabolic dysfunction and are more prevalent in centenarians.
These studies can only highlight associations rather than show causation, so we don’t yet know whether losing F. Prau leads to frailty or if the bacteria is lost as a result of frailty. “The gut microbiome is such a complex system,” says Lochlainn.
“We’re getting better at having these rough ideas of what’s good and what’s bad, but we’re still quite far away from being able to take an individual and say, ‘Oh, you clearly need more of x, y and z.’”
Too many of these bacteria is bad news
Streptococcus and Heliobacter pylori bacteria are commonly found in our guts. In small amounts, they’re harmless. But if gut health is compromised, a harmful imbalance, or gut ‘dysbiosis’, occurs, and species like these can reproduce rapidly, potentially reaching levels that, in extreme cases, can be fatal.
It’s another reason why balance is so important for a healthy microbiome – having too many ‘bad’ bacteria leaves less room for the ‘good’ ones to thrive.
Certain potentially harmful or pro-inflammatory bacteria tend to be found in higher abundance in older adults, says Wang, “such as Klebsiella, Streptococcus, Enterobacter and Rhodococcus.”
But he also notes that pathogenic bacteria from the Proteobacteria group – associated with inflammation and dysbiosis – are depleted among centenarians.
You might think that pathogenic bacteria would proliferate in the guts of centenarians, but experts suspect a diet favouring fruit, veg and fermented foods helps these superagers keep a lid on them.
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How the gut could be keeping superagers' brains young
The older we get, the greater our risk of degenerative brain diseases such as Alzheimer’s and Parkinson’s disease (PD), which together affect over 65 million people globally. Emerging research indicates that the gut could play a significant role in reducing that number.
The stomach has its own nervous system, which is connected to the brain via the vagus nerve and through this so-called gut-brain axis, gut health influences brain function and mood. Similarly, but following that axis in the opposite direction, stress can give us stomach aches.
People living with PD tend to lack certain beneficial bacteria. Disruptive protein clumps called ‘Lewy bodies’ that form in the brains of PD patients have also been found in their guts.
Meanwhile, the gut microbiomes of Alzheimer’s patients foster more inflammation-causing bacteria. Memory problems have even been passed on to young animals by transplanting faeces from Alzheimer’s patients into their guts.
All of which is to say: maintaining a healthy gut may be good for both our physical and mental longevity.
Improving gut health could make you stronger
Muscle wastage is the enemy of longevity. This is why we’re told to start pumping iron in middle age. Losing muscle mass as we get older “contributes to people losing their independence,” says Lochlainn.
The less muscle mass we have, the harder it is for us to mobilise and perform everyday tasks, such as lifting and carrying shopping.
“It also makes us more frail, because muscle is protective for things like falling and breaking your hip.” Recovering from falls in old age can actually start a whole cascade of deterioration.
But evidence is now mounting that gut health plays a role in maintaining healthy muscle. Researchers have found that probiotic supplements full of good bacteria can improve muscle strength in older people.
Like most things, “the effects are probably complex and multifactorial,” says Lochlainn.
“The gut microbiome metabolises your amino acids – it takes in your protein, which is important for your muscles to grow – and plays a role in balancing your insulin and glucose, which, again, is really important for muscle. So, it’s probably [affecting your muscles] through a range of different pathways.”
Taking prebiotic fibre can also help your gut bacteria and, by association, your muscles. “There was a really nice study that showed older people living in a care home were able to improve their grip strength by taking a prebiotic,” says Lochlainn.
As in Lochlainn’s own prebiotic study looking at cognition, the fibres used were an inulin and Fructooligosaccharides (FOS) combination, usually taken in powder form.
“They’re just simple fibres, but they’re potentially going to improve your cognition and they’re potentially going to improve your muscle strength,” she says.
Following a superager's lifestyle could help you emulate their gut health
Most centenarians “tend to have very simple and regular lives,” says Wang. “They often follow a natural diet rich in fibre from foods like vegetables, corn and sweet potatoes.
“They maintain a regular lifestyle and embrace optimism. Rarely do they consume ultra-processed foods, although some may still smoke or drink.”
Lifestyle choices that we all know are good for systemic health are good for the microbiome. Gut health, and the longevity associated with it, is yet another reason to prioritise diet, exercise, sleep hygiene and mental health.
“I know, it’s a bit boring,” says Lochlainn, “but it’s actually those things [that can make a noticeable difference].”
One of the benefits of studying superagers’ guts is that it might motivate us to live what we know to be a healthy life. Exercise and sleeping well are all positively associated with gut (and holistic) health.
As is being social – it’s a balm for our nervous systems, which are embedded in the gut, and increasing exposure to rich microbial diversity.
Diet-wise, you’ve probably already heard that consuming probiotic- and prebiotic-rich ferments like kefir and sauerkraut are great for your gut.
Branyas ate three servings of natural live yoghurt a day. Natural sources of the best prebiotic fibre include artichokes, oats, garlic, onions, asparagus and leeks.
How to get the things your diet doesn't provide
Although consuming a diet that’s high in fibre should be a priority for overall good health, both Wang and Lochlainn think there’s a place for probiotic and prebiotic supplements.
Lochlainn sees prebiotics as potentially more impactful. “It’s not like with the probiotic, where you’re trying to get active bacteria to stay alive to the colon – a lot of it probably gets killed off in the stomach [before it reaches the colon].
"That’s not so much of an issue with prebiotics, because they’re not active bugs. They’re just fibres that we can’t digest.”
Supplements are helpful in this instance because some of these fibres can be tricky to find in the diet.
“They’re not always in the things you’d normally eat in a British diet – like artichokes and so on,” says Lochlainn. “But a lot of these supplements are commercially available and they’re not super expensive. So why not give them a go?”
One thing to be aware of is that any positive effects on the microbiome through supplementing or other lifestyle changes, will probably only last as long as the intervention.
“If you decide, ‘I’m gonna start eating more kefir’, you need to sustain that,” says Lochlainn. “You can’t just do it for six weeks [and expect the benefits to persist].
"There are some cases where the short-term effects might be useful – recovering after a course of antibiotics, for example. But in general, a lot of interventions do seem to revert if the change isn’t upheld.”
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