Information technology manager Jaxon Ji, 44, used to treat himself to soft drinks such as ice-cream soda, orange and Sprite three to four times a week.

"But I found them too sweet and decided to look for alternatives. I was also concerned if there were too many chemicals in them."

Today, instead of soft drinks, he drinks water kefir, a fermented drink made from water kefir grains, and Jun kombucha tea, which is fermented green tea and honey.

He says: "I used to have severe rhinosinusitis. But I don't get it anymore. I hardly get sick and even if I do, it's just sniffles and throat itch, which do not require me to take time off work."

Mr Ji is among the growing number of people who ferment their food and drinks at home. They believe that these foods contain probiotics which have health benefits, especially for the digestive system. Users have reported better bowel movement and improved skin and immunity.

Among the most popular food is milk kefir, which is not just consumed by humans, but also fed to animals by some pet owners. It purportedly helps their fur to grow, improve their skin and digestion and has a calming effect on them.

Home fermentation is a growing niche hobby in Singapore. The Facebook group SG Fermentation Friends has more than 1,600 members. It was founded last year by civil servant Mak Shao Xuan, 35, and two other friends who were home brewers and wanted to promote home fermentation.

Members meet for picnics where people bring along fermented products for others to sample. Ms Mak and other invited speakers from overseas also conduct workshops, at a fee ranging between $100 and $150 for each participant.

Another Facebook group, the Water Kefir And Milk Kefir Grains Blessing (SG), was founded last year by a few mothers.

They were fermenting kefir grains at home to boost their children's health, but ended up with too many grains and decided to set up a Facebook group to give them away.

The group now has more than 2,500 members. While made up largely of mothers, it has also drawn pet owners who want to feed kefir to their pets.

Both groups have a listing of members who donate free starter cultures.

Starter cultures include kefir grains and "scobies". A scoby, short for "symbiotic colony of bacteria and yeast", is a piece of fibrous tissue that comes in various colours, including cream, yellow or dark brown. Like kefir grains, they encourage fermentation.

With each fermentation, scobies and kefir grains multiply, hence people end up with extra pieces, which they can donate.

Whether or not the fermented foods have health benefits, experts take a cautious view.

Fermented foods stay fresher longer than the usual foods, says Professor William Chen, director of Food Science and Technology Programme at the Nanyang Technological University.

Fermentation occurs when micro-organisms such as bacteria or yeast convert organic compounds such as sugars into alcohol or acetic acids.

"The acidic environment kills off 'bad' bacteria such as those that cause food spoilage and ensures that good bacteria such as potential probiotics survive longer."

The crux of the issue is "potential probiotics". On the one hand, probiotics have been shown to help with a multitude of health issues, especially digestive health.

But without scientific testing, one cannot assume micro-organisms in home-fermented foods are probiotics, says Associate Professor Liu Shao Quan from the Food Science & Technology Programme at the National University of Singapore.

He adds: "True probiotics have to be able to survive the journey through the very acidic stomach to colonise the intestines."

Meanwhile, those who wish to continue to eat or drink fermented food should ensure that they start slowly and increase their intake gradually to allow the body to get used to it, says Ms Lynette Goh, a senior dietitian from the National Healthcare Group Polyclinics.

She says: "If it is introduced too quickly, bloating or other gastrointestinal symptoms may occur."

She adds that it is also important to practise food safety when preparing fermented foods.

"For instance, vegetables used for fermentation should be fresh and washed thoroughly to avoid bacteria contamination. Other usual basic food hygiene practices such as washing hands before preparation should also be followed."

To ensure food safety, stay-at- home mother Beth Chan, 39, says she washes her glass bottles, plastic sieve and plastic spoon before she starts preparing the water kefir grains for fermenting.

She has been giving half a cup of water kefir every day to her children, aged two and five, since last April. She and her husband drink two cups daily. They have experienced no adverse effects so far.

She says: "My kids poo more each time, while my husband's and my bowel movements became more regular. My husband's mouth ulcers also disappeared."

Besides humans, animals have also purportedly benefited from home-brewed food.

Ms Lois Liu, 57, who runs a hair products company, has been giving one teaspoon of milk kefir to each of her four dogs every day since August this year. Once a week, she also gives them a treat, which is water kefir flavoured with fruit.

She says: "They had been suffering from problems ranging from skin rashes and bald patches to bad breath and constipation and had to visit the vet once a month. I was trying to find other ways to help them besides medication and home-cooked food when I read about kefir in July on a Facebook group."

After more than a month of taking milk kefir daily, she says their symptoms have improved.

She says: "Their fur started to grow, there was no more bad breath and constipation, and I have not taken them to the vet since."

From milk kefir to kombucha and sauerkraut

When her three children came down with a bout of vomiting and diarrhoea in June this year, stay-at-home mother Kristal Lynn Chang fed them some milk kefir that a friend had given her.

Milk kefir is a fermented milk product that tastes like yogurt and is said to be rich in probiotics. It is made by fermenting milk kefir grains in milk.

Her children, who are aged 16 months to four years old, recovered the next day. Since then, Ms Chang, 36, has been making milk kefir for them.

She also went on to ferment various things, from yogurt, gingerbug soda and black ginger, to koji, kimchi, kombucha and sauerkraut.

She picks up tips from YouTube videos and Facebook groups and meets other home brewers to swop information.

Her enthusiasm was so great that her fridge ran out of space and she had to get a larger one to store all her fermented goodies.

But it has been worth it, she says, as she saves money and has seen improvement in her family's health.

She no longer buys yogurt and kimchi for her family as she can now make her own.

She has also stopped buying soft drinks. She and her husband, 44, an IT professional, drink water kefir, which tastes like soda without the artificial additives, as a replacement.

"I feel that our skin and digestion have improved and we seldom fall sick," she says.

Fermenting has also opened her eyes to other D-I-Y health products.

For instance, she has started an edible garden in her five-room Housing Board flat and is learning how to grow her own food.

She is also learning to make her own shampoo, shower gel and facial moisturiser using natural ingredients.

She says: "When you make your own, you can control what goes into it and avoid any harmful products.

"As a mother, I want to give my kids the best that I can."