Fermented Foods for Gut Health: Curd, Idli, Kanji and More

Walk into a supermarket today, and you'll find kombucha in glass bottles, kimchi in jars and kefir in the refrigerated section. Social media is full of people recommending these foods for better digestion and a healthier gut. Some even come with a surprisingly high price tag. Yet you might already be eating fermented foods without giving them much thought. The curd setting in your kitchen, the idli batter left to ferment overnight and a freshly made dosa all have something in common with these trendy products.

They're made through fermentation, a natural process in which microorganisms such as bacteria and yeast change the food's composition. So, are fermented foods for gut health really as beneficial as people claim? Can everyday Indian foods offer similar benefits, or are imported options worth trying? The answer depends on the food, the microbes it contains and what research actually tells us about their effects on gut health.

What counts as a fermented food?

An international panel of scientists from the International Scientific Association for Probiotics and Prebiotics (ISAPP) set out a clear definition in 2021. Fermented foods are foods made through desired microbial growth and enzymatic conversions of food components. In simple words, bacteria or yeasts are allowed to grow in the food on purpose. They change it as they feed. That change is what turns milk into curd, rice and urad dal into idli batter and carrots into kanji. The microbes break down some of the sugars, make the food sour, help it keep longer and add new flavours.

Not every fermented food still has live microbes when you eat it. The same panel points out that foods such as bread are baked after fermentation, which kills the microbes. Idli, dosa and dhokla are steamed or cooked, so most of their microbes do not survive the heat either. They are still fermented foods. Fermentation has already changed them for the better. They are just not a source of live bacteria.

Are fermented foods the same as probiotics?

They overlap, but they are not the same. The ISAPP panel took care to separate the two. A probiotic is a live microbe, in a known amount, that has been shown to do you good. A fermented food may contain many live microbes, a few or none. The types and numbers vary from batch to batch and from home to home. Think of it this way. Homemade curd is a lively, changing mix. A probiotic capsule is a measured dose of named strains. Both have a place. Our Aora guide to probiotics vs prebiotics explains how live microbes and the fibre that feeds them work together.

What does the research say about fermented foods for gut health?

One of the most interesting studies on fermented foods came from Stanford University in 2021. Researchers followed 36 healthy adults for ten weeks, dividing them into two groups. One ate more fibre, while the other increased their intake of fermented foods such as yoghurt, kefir, kombucha and kimchi to around six servings a day. The results were encouraging. People in the fermented food group developed a greater variety of gut bacteria and showed reductions in several markers of inflammation. The high-fibre group did not show the same increase in bacterial diversity during the study.

Interestingly, yoghurt and fermented vegetable brine drinks were among the foods most strongly associated with greater gut bacterial diversity. For Indian readers, these are familiar concepts, similar to everyday foods such as curd and traditional fermented drinks like kanji. However, the study was small, with just 18 participants in each group. It also examined fermented foods commonly eaten in the United States, so we cannot assume every Indian fermented food produces the same results. What does this mean for you? Fermented foods may help support a more diverse gut microbiome, but the evidence is still developing. Including foods such as curd in a varied diet is a reasonable starting point, without needing to spend more on imported alternatives.

Traditional Indian fermented foods that support gut health

You don't have to look far to find fermented foods in India. From curd and buttermilk to idli batter and traditional vegetable drinks, fermentation has been part of Indian cooking for generations. A review by researchers at Pondicherry University highlights traditional foods such as dahi, gundruk, sinki and kanjika as sources of lactic acid bacteria, microorganisms involved in fermentation. The benefits vary depending on how each food is prepared and whether live microbes remain when you eat it. Here are some familiar options worth knowing about.

Curd and buttermilk

A bowl of homemade curd or a glass of chaas is one of the easiest ways to include fermented foods in your daily diet. When prepared with live cultures, both can contain beneficial bacteria. Curd may also be easier to digest than milk for some people with lactose intolerance because fermentation breaks down part of the milk sugar. Research supports this benefit for yoghurt containing specific live cultures, which can improve lactose digestion. However, the effect depends on the cultures present, so not every homemade curd will offer exactly the same benefit.

Idli, dosa and dhokla

These familiar breakfast foods are made using fermented batter. During fermentation, microorganisms break down some of the ingredients, changing the batter's texture, flavour and nutritional composition. A study examining idli batter found increases in certain B vitamins, including thiamine, riboflavin and folate, during fermentation. However, fermented doesn't always mean probiotic. Cooking idlis, dosas and dhokla destroys most of the live microbes, so they shouldn't be considered direct sources of live probiotic bacteria. They can still be part of a nutritious, balanced diet.

Kanji and fermented vegetables

Kanji is a traditional North Indian drink commonly prepared with black carrots, mustard seeds, salt and water. The mixture is left to ferment until it develops its characteristic tangy flavour. Other Indian regions have their own fermented vegetables. In Northeast India, for example, gundruk is made from fermented leafy greens, while bamboo shoots are fermented in several traditional preparations. These foods share similarities with kimchi and sauerkraut because they rely on microorganisms to develop their flavour and texture.

The main advantage is variety. Including different traditional fermented foods can add flavour and diversity to your diet without relying on expensive imported products. Just remember that their live bacterial content and health effects can vary, and safe preparation and storage are important.

What about kombucha and kefir?

Kefir is a fermented milk drink with a longer history than its sudden fame suggests. A 2023 review of trials found it appears safe for generally healthy people, though the evidence for specific health effects is still limited. Kombucha is fermented sweet tea. When researchers searched the literature in 2018, they found only one study reporting its health effects in humans. Both can be part of a varied diet for healthy people. They are simply not more proven than the curd you already make at home. They also cost a good deal more.

Easy ways to add fermented foods to your daily diet

You don't need to change your entire diet or spend money on expensive fermented products. A few simple additions to your regular Indian meals can help you enjoy more variety.

1. Include curd with your meals. Have a small katori of homemade curd with lunch or dinner on most days, if you tolerate dairy well.

2. Choose chaas over sugary drinks. A glass of plain or lightly salted buttermilk makes a refreshing afternoon drink. Add roasted jeera or coriander for flavour.

3. Enjoy fermented breakfasts. Include idli, dosa, appam or dhokla in your weekly meals. Although cooking removes most live microbes, fermentation still changes the batter's composition.

4. Try traditional kanji. When black carrots are in season, properly prepared kanji can add variety to your diet. Follow safe fermentation and storage practices.

5. Keep pickles as a side dish. Traditional pickles can add flavour, but many contain plenty of salt and oil. Also, not all Indian pickles are naturally fermented or contain live bacteria.

6. Pair fermented foods with fibre. Include dal, vegetables, whole grains and fruits. Fibre helps nourish the beneficial bacteria already living in your gut.

Start with small portions, especially if you're not used to fermented foods. Increasing them too quickly may cause temporary gas or bloating. You don't need to eat every fermented food on this list. Choose what suits your taste, digestion and everyday routine.

Also read: Morning Bloating vs Evening Bloating: What the Timing Can Tell You.

When should you be careful with fermented foods?

Fermented foods are generally safe for healthy people, but a few precautions are worth keeping in mind.

• Weakened immune system: If you're undergoing cancer treatment, have had an organ transplant or have a serious illness, speak to your doctor before taking probiotics or adding foods containing live cultures. The NCCIH warns that probiotics carry greater risks for people with weakened immune systems.

• High blood pressure or kidney disease: Watch the salt content in pickles, kanji and salted buttermilk, especially if you've been advised to limit sodium.

• Home fermentation: Use clean equipment and follow safe preparation methods. Discard anything with visible mould, a rotten smell or other unusual signs of spoilage.

• Pregnancy: Avoid fermented dairy products made from unpasteurised milk. The NHS warns that these can carry harmful bacteria, including Listeria. Use pasteurised milk when making curd.

• Probiotic supplements: If you take regular medicines or have an underlying condition, check with your doctor before starting a supplement.

When should you see a doctor?

Occasional bloating may settle on its own, but persistent or worrying digestive symptoms deserve medical attention. The NHS recommends:

1. Emergency care: If rectal bleeding is heavy or won't stop, or you notice large blood clots. Call 112 in India or visit the nearest emergency department.

2. Urgent medical attention: If your stool is black or dark red, or you have bloody diarrhoea.

3. A doctor's appointment: If blood in your stool lasts three weeks, bowel habits change for three weeks, or you experience unexplained weight loss, unusual tiredness, abdominal pain or a lump. Blood in a child's stool also needs medical assessment.

Also read:

• Are Probiotic Supplements Safe? What You Should Know

• IBS and Blood in Stool: What It Could Mean

The oldest gut habit in the house

The wellness world has rediscovered something your kitchen never forgot. The bowl of curd set with a spoon from the last batch, the batter left to rise near the stove and the jar of kanji in the winter sun were gut care long before anyone called them that. Keep them on your plate, add variety where you can and let the trend catch up with you.

Sources

• The ISAPP consensus statement on fermented foods (Nat Rev Gastroenterol Hepatol, 2021)

• Gut-microbiota-targeted diets modulate human immune status (Cell, 2021)

• Traditional Indian fermented foods: a rich source of lactic acid bacteria (Int J Food Sci Nutr, 2013)

• Preparation of idli batter, its properties and nutritional improvement during fermentation (J Food Sci Technol, 2011)

• The effects of kefir consumption on human health: a systematic review of randomized controlled trials (Nutr Rev, 2023)

• Kombucha: a systematic review of the empirical evidence of human health benefit (Ann Epidemiol, 2019)

• NCCIH: Probiotics, usefulness and safety

Medical Disclaimer: This article is for general information and is not a substitute for advice from your doctor. Speak to a qualified healthcare professional before starting any supplement, especially if you are pregnant, breastfeeding or taking medication.