Your gut microbiome is a vital support system for mental and physical health, supplying the body with all-important nutrients and helping tune the immune system. And we are now realising how vital this is for healthy ageing too.
As we get older, the balance of microbes in our gut changes. There are declines in beneficial types, such as the anti-inflammatory Faecalibacterium, and an increase in species that lead to more inflammation, which is implicated in multiple age-related conditions, including heart disease, cancer and cognitive decline. , with participants ranging from an isolated rural population in India to a wealthy semi-urban community in Italy, show striking similarities in the microbiome signatures of old age. One key finding is that people who have no significant health concerns in older age have an abundance of distinct beneficial microbes that are lost when there is a shift to physiological decline.
It isn鈥檛 clear whether the microbiomes of healthy older people are driving their vitality or are a result of the way they live, but an astonishing in mice by at University College Cork, Ireland, and his colleagues found that transplanting gut microbiota from young animals to elderly ones reversed age-associated impairments in brain function.
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All this emphasises how crucial it is to look after our gut microbiome and keep it as beneficial as possible. But how exactly should we go about this?
How to keep your microbiome healthy
For a start, we need to know what a healthy microbiome looks like. This is no mean feat. 鈥淭here are no overt physical signs that can be reliably used to tell if your microbiome is health-associated or not,鈥� says , also at University College Cork.
Even when researchers analyse the myriad different kinds of microbes in our guts, it is hard to work out exactly what is doing what. 鈥淒espite the growing science linking the gut microbiome and the chemicals it produces with dozens of health outcomes, what defines an optimum or 鈥榟ealthy鈥� gut microbiome is still not absolutely clear,鈥� says at King鈥檚 College London, who is a co-founder of personalised nutrition company ZOE.
One of the most common measures of gut health is microbial diversity, with more regarded as better in general. But this isn鈥檛 foolproof. The problem is that even having many unhealthy bacteria could make the microbiome more diverse, says Spector, so diverse doesn鈥檛 always mean better. And some groups, including vegans, tend to have a diet rich in plants and have lots of good bacteria, but also have lower diversity, says Spector. Another more recent approach is to analyse the thousands of chemical metabolites of microbial fermentation in the gut, he says, 鈥渂ut we currently don鈥檛 understand most of their functions, and many changes can be very short term鈥�.
To address these issues, the ZOE team joined forces with researchers at the University of Trento in Italy to devise a new measure of microbiome health. It is based on the genomic sent by ZOE users, which uncovered hundreds of hitherto unknown gut species. This data was then linked to dietary and health patterns to provide a new way to compare the ratio of 鈥済ood鈥� bacteria to 鈥渂ad鈥�. 鈥淭his performed much better than traditional measures of diversity in categorising healthy guts, and for charting improvements with diet,鈥� says Spector.
This kind of research is helping to build a better picture of the microbial make-up associated with good health and the factors that influence such a state. Unsurprisingly, diet is key. 鈥淚ncreasing the diversity of the foods we eat increases the diversity of the microbiome,鈥� says Cryan.
The best foods for your microbiome
To get that diversity, Spector recommends eating a variety of plants, ideally 30 different types per week, as well as 鈥渆ating the rainbow鈥� 鈥� consuming a mix of colourful plants high in substances called polyphenols that are linked with high microbiome diversity. There is also that fermented foods, such as yoghurt, kefir, kombucha and kimchi, could increase diversity and dampen inflammation 鈥� so if you enjoy those, add them to your diet.
Increasing the amount of fibre you consume is also helpful, assuming your digestive system can tolerate it. 鈥淔ibre is broken down by lots of microbes and provides lots of key molecules,鈥� says Cryan.
There are things to avoid eating too. 鈥淓xcessive amounts of sweeteners 鈥� artificial sweeteners in particular 鈥� emulsifiers and ultra-processed foods all have negative effects on the microbiome,鈥� says Cryan.
It isn鈥檛 just what you eat, but when. A number of recent studies show that can have a beneficial impact on microbiome composition, with knock-on health benefits. For example, one found that a carefully monitored fast over several days encouraged species of gut microbes that produce beneficial compounds called short-chain fatty acids. In combination with a Mediterranean-style diet, which leans heavily on plant oils, wholegrain foods, fruit and vegetables, this resulted in a greater reduction in blood pressure and weight in people with metabolic syndrome (those who have diabetes, high blood pressure and obesity), compared with the dietary intervention alone. 鈥淕ive your gut an overnight fast of 12 to 14 hours to help function,鈥� recommends Spector.
Stress and the microbiome
Other factors have an impact. Our gut microbes are , for example. Stress can alter the composition of the microbiome, says Cryan. But it is a complex, two-way process. 鈥淪tress can affect the gut, and then the gut can impact how we deal with stress,鈥� he says. Stress can also by increasing the permeability of the gut lining, allowing bacteria to enter the bloodstream and trigger inflammation.
Poor sleep can also take a toll on the gut. This is because the microbiome has a daily cycle, says at the University of Pennsylvania. 鈥淪leep loss will disrupt rhythms in the microbiome.鈥� Even small disruptions to sleeping patterns can have an impact. Spector and the ZOE team, for instance, have found that social jet lag, where a different sleep pattern is adopted at the weekend compared with on weekdays, is associated with .
How your social life affects your microbiome
Your social life 鈥� or lack of it 鈥� can also help shape the inhabitants of your gut (see 鈥淗ow your microbiome is shaped by your friends, family, lovers and pets鈥�). We pick up some of our microbes from contact with other people and our surroundings, so isolation can cause our microbiome to become less diverse. In fact, this is thought to be one cause of the lack of microbial diversity associated with unhealthy ageing. 鈥淭he social microbiome is acquired from family, friends, the environment,鈥� says O鈥橳oole. 鈥淒on鈥檛 be afraid to get out there, meet people, work in your yard.鈥�
And it is for these reasons that Cryan has one final tip: get a dog if your circumstances allow it. 鈥淭he other thing that鈥檚 good for your microbiome is having a pet,鈥� he says. One , for instance, found their pet boosted the composition of their microbiome in positive ways.
The more we learn about the microbes in our gut, the more ways we find to tweak them in a healthy direction. 鈥淚t鈥檚 clear from our own and other research that looking after our gut microbiome should be a priority in public health,鈥� says Spector.
Speak to your doctor before seeking new treatments for medical conditions.
