You know that a fibrous diet is good for you — but fermented food might actually better improve gut health.
There’s been a heightened focus on gut health over the past few years, as more and more research shows the link between a healthy digestive system and our overall wellbeing. With that, the benefits of high fibre diets have been thrust into the spotlight - and rightly so.
But research shows we might be missing a trick by putting all the emphasis on beans and vegetables. A 2021 study led by Dr Justin Sonnenburg, associate professor of microbiology and immunology at Stanford University, found that fermented food might actually be better than fibre for improving gut diversity and reaping the associated health benefits.
In the study, researchers randomly allocated people a high-fibre diet or a fermented food diet that included foods such as kefir, kimchi and probiotic yoghurts. While both groups saw improvements to their microbiome, only the fermented food group increased the diversity of the strains of bacteria that lived in their gut.
Researchers said that it was a clear example of how simple changes to our diets can remodel the microbiota for good – particularly as the body’s immune system changed with their microbiome. There was a reduction in levels of 19 inflammatory markers, including those linked with diabetes and chronic stress, suggesting that better gut health improves immunity.
There are so many benefits to fibre, from keeping you regular (which Sonnenburg’s team confirmed in their study) to stabilising blood sugar levels. But the study showed that those who ate high-fibre diet without a pre-existing diverse gut microbiome didn’t manage to reap as many benefits from the nutrient.
That’s because stool samples were shown to contain higher levels of carbohydrates, suggesting “incomplete fibre degradation”. Essentially, their gut bacteria couldn’t break down the extra fibre to reap the benefits of it.
Speaking about the research on the Huberman Lab podcast, Sonnenburg said, “It may be that many of us in the industrialised world have a microbiome that’s so depleted now that even if we consume a high fibre diet, at least for a short period of time, we don’t have the right microbes in our gut to degrade that fibre.”
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Researchers noted that it might simply take longer than the six weeks of their study to see the gut respond to the extra nutrients, but the big takeaway here is that we need both fermented food and fibre to really reap all of the benefits. So the next time you reach for a can of chickpeas, make sure you top them with a forkful of kimchi.
Dr Sonnenburg also added that avoiding items that are sweetened during manufacturing is best for your microbiome. “We instructed people to eat non-sweetened yoghurts. A huge pitfall in this area is you can have a yoghurt loaded with bacteria, the base of it is really healthy, and then a tonne of artificial flavouring and sugar is loaded on top of that to mask the sour taste of fermented foods, which is hard for some people to become accustomed to.”
He explained that when he started introducing more fermented foods into his own diet, his younger daughters didn’t enjoy the sour taste of plain yoghurts.
“We would mix in a little maple syrup or honey and gradually we reduced that over time to the point where their palate adjusted and now they just really like plain yoghurt. Getting used to that sour flavour is difficult but people really should try to stay away from those fermented foods that are loaded with sugar,” he added.
Plus, many foods in brine have a high salt content that should be monitored. And not all brined foods are actually fermented - so make sure you check before loading up on pickles.
How to eat more fermented foods
“The three simple tips that come up time and time again from scientists, doctors, dietitians and nutritionists are increasing variety, upping your fibre and trying ferments,” say experts from The Gut Stuff. So managing to get in as many different sources in is your best bet.
“If you keep all the different microbes happy, they can do incredible things like help to control your blood sugar, produce vitamins, manage cholesterol and hormonal balance, prevent you from getting infections, control the calories that you absorb and store, communicate with your nervous system and brain, influence your bone strength and so much more,” they add.
They recommend trying some of the following:
- Sourdough, which contains lactobacillus and yeasts to produce acetic and lactic acid that gives it its tang.
- Sauerkraut, kimchi and other fermented veg – these ferments utilise salt to create the perfect briny environment for beneficial bacteria to thrive.
- Miso, a paste from fermented soy, counts as a fermented food and is brilliant in soups and salad dressing.
- Kefir grains ferment the lactose in milk and although it has a sour taste it goes well in place of yoghurt.
- Kombucha – a fizzy fermented tea – is popular enough to get on supermarket shelves.
- Live yoghurt – look for ‘live yoghurt’ or ‘live cultures’ on the label as most yoghurts you’ll find on the shelf will be pasteurised (heat-treated) with bacteria added back in
Chloe Gray is the senior writer for stylist.co.uk's fitness brand Strong Women. When she's not writing or lifting weights, she's most likely found practicing handstands, sipping a gin and tonic or eating peanut butter straight out of the jar (not all at the same time).