If you've seen social media posts by people raving about their home-brewed kombucha or amazing kimchi and dismissed them as nothing more than the latest food trend, it's time to think again.
They are just two examples of fermented foods, which can provide huge benefits to your gut health by adding lots of good bacteria to your diet.
From sauerkraut to kefir, miso to jun, the world of fermented food is rich and varied - and increasingly popular.
Dr Michael Mosley admits that just a year ago he knew "absolutely nothing" about fermenting and the benefits of fermented food.
Having reported on fermenting in Trust Me I'm a Doctor, he is now among the voices saying we should be including more fermented foods and probiotic drinks in our diet.
In his new book , Dr Mosley writes: "One of the reasons why fermented foods are so good for the gut is that, gram for gram, they contain a huge number of different microbes. The microbes in fermented foods are also far more likely than most other bacteria to make it safely down into your colon because they are extremely resistant to acid, having been reared in an acidic environment."
Dr Michael Mosley puts fermented foods to the test. Source: BBC Worldwide
Dr Mosley and his wife, Dr Clare Bailey, are now fermenting at home, and have changed their eating habits as a result.
"My wife has got into it with massive enthusiasm, I must say, and I'm doing it as well. She's been making some kimchi and making some sauerkraut and things like that... and they're delicious," Dr Mosley tells SBS.
"It's nice to think you're getting a good old burst of healthy microbes hitting your gut, but also these things are a delicious addition to the foods you eat. It's like a whole new food regime has hit our house. It's a whole new foodie experience."
Since becoming a late adopter to home fermenting, he is encouraging others to try it; it's among many issues relating to gut health that he tackled in a recent episode of Insight:
As a busy GP, Dr Bailey has started to use food, including fermented foods, to help patients suffering from things like Type 2 diabetes and irritable bowel syndrome.
"She says it's just miraculous - it's been one of the most rewarding things of her career," Dr Mosley says.
"The assumption is this is just going to target the elite and nobody else is going to pay attention, but her patients are generally a deprived, poorer sector of the UK population, and she said they get it, they grasp it, they want to do something about it. They don't all, but she said it's just astonishing how much difference it makes."
This isn't news for Sharon Flynn, who turned to fermented food when her daughter Lulu got very sick when she was four years old.
Doctors couldn't find the source of her illness, and she was prescribed dose after dose of antibiotics, including one particularly strong type which the doctor told her would "kill everything".
"From the time that she took that one, she couldn't keep any food down, she vomited it all," Flynn tells SBS.
"I actually started going to the emergency room with the vomiting."
When a friend recommended she include probiotic and fermented food in Lulu's diet to heal her gut, Flynn was more than ready to try: "I just wanted her to happy and healthy again."
She started by giving her more yoghurt and miso soup, and cutting back on simple carbohydrates, before getting more adventurous and trying kefirs and krauts. Before long Lulu started to crave the sour taste associated with these fermented foods.
"She definitely would come in the morning at 6.30am and say 'Can I have my drink?' That was water kefir and milk kefir," Flynn recalls.
"I never treated it like a medicine, or said you have to have this. It was a long-term lifestyle change."
Lulu recovered well, and Flynn started making fermented foods for her friends. It was the accidental start of her business, .
She swears by milk kefir to treat illness, but stresses that most bought probiotic drinks and fermented foods contain little live bacteria because they have been forced to comply with food safety regulations.
"When you make these things at home, particularly kombucha, there's alcohol in naturally fermented drinks, but only about 1.5-2 per cent, and you don't care about it because it's so low, and you'll get this naturally carbonated beautiful drink," says Flynn, who shares her recipes in her book .
"All the [mass-produced] kombuchas, they water the product down, they ferment it so that it doesn't have any bubbles, and then they force-carbonate it, so it's just like a regular fizzy drink - and they're doing that to be compliant."
Source: Hardie Grant Books / Tara Pearce / James Broadway
She says the same goes for home-made verses shop-bought sauerkraut.
"Instead of making it how I would at home - just cabbage and salt and seeds - they want you to chop the cabbage, bleach it with a citric acid, which kills the bacteria that you need, and then they would like you to buy a starter culture and add the starter culture.
"If you make it at home, it's better for your gut. If you're on a healing path, then homemade or knowing a small producer [is best]."
Get Sharon's kraut recipe - and smoky jalapeño kraut - .
Source: Hardie Grant Books
This gels with Dr Mosley's research findings. He analysed 10 products and 60 per cent of them had nothing living in them.
"The danger is if you buy these mass-produced things, they've been pasteurised to death, and therefore there's nothing there," he says.
Dr Mosley was also part of a study that looked at supermarket fermented milk drinks or milk kefir.
"We got 30 people and we randomly allocated them to one of those yoghurty drinks or drinking kefir, and when we looked at their poo samples, basically those taking the yoghurt product, there was no discernible change at all in their gut biome, despite having consumed one of these things every day for a month," he tells SBS.
"Whereas those taking the fermented kefir saw huge changes. So my concern is that manufacturers are just going to jump on this and start pumping out all sorts of strange and dodgy concoctions and label them prebiotics, probiotics and things like that, and yet few of them have any substantial evidence behind them."
Felicity Evans started making her own gut-friendly elixirs after a bout of debilitating illnesses, including Dengue fever, glandular fever and malaria, and successive courses of antibiotics left her bedridden and lethargic.
"After the birth of my second baby, I had mastitis for a year. I had eight courses of antibiotics in eight months and I had no idea that after antibiotics you really need to do something for your gut.
"I was 29, and I felt 20 years older. I just thought, screw this, this is not the kind of wife and mother I want to be. So that's when I started to research. I started to learn about the gut and how important it is."
She started by making her own water kefir, and found that within days her health started to improve.
"The results were quite dramatic. My energy did shift, I felt lighter, and my digestion was better," she says.
She started her own company, , and is now sharing the recipes for water kefirs, jun, kombucha, beet kvass and many more in her book .
Get Felicity's recipes for (left), (middle) and .
Source: Murdoch Books / Rob Palmer
Evans says these days people are much more accepting and understanding of fermented food and drinks, and the role they can play in good gut health.
"Four or five years ago, we didn't have all the knowledge we do now. My Birkenstocks [shoes] were weird, my fermenting was weird, I was known as 'the fizzy drink lady', and people couldn't pronounce kombucha or kerfir," Evans says.
"Now probiotic drinks are to 2017 what green smoothies were to 2014. They have become the cornerstone of my family's excellent health."
