From intermittent fasting and probiotics to “gut detoxes” and so-called superfoods, nutrition advice is everywhere. Social media has turned food and gut health into a stream of competing claims – some rooted in science, others driven more by trends than evidence. But with so much advice at our fingertips, a basic question remains: what does the science actually say?

The gut is home to trillions of microorganisms that interact with the food we eat and play important roles in digestion, metabolism, immune function and overall health. 

A BMJ study highlighted the growing evidence that the gut microbiome plays an important role in human health, noting that it “influences many areas of human health from innate immunity to appetite and energy metabolism.” The researchers also emphasised that “Fibre is a key nutrient for a healthy microbiome” and that fibre consumption is associated with beneficial effects in several health contexts. 

At the same time, intermittent fasting and time-restricted eating have emerged as popular approaches to weight management and metabolic health. But the evidence is far more nuanced than the promise of a single eating window. Randomised trials have produced mixed findings: while some studies have reported benefits from early time-restricted eating, others have found that restricting the eating window does not necessarily lead to greater weight loss or metabolic improvements than conventional meal timing.

So, does meal timing really matter? Can fasting change the gut microbiome? Are probiotics necessary for everyone? Do “detox” diets have a role to play? And are expensive supplements and “superfoods” actually better for gut health than ordinary, fibre-rich foods?

Speaking at First Check LIVE’s second episode, ‘Food, Fasting & Gut Health: What Does the Science Say?’, held on Wednesday, Dr Anupam Sibal, Paediatric Gastroenterologist  & Group Medical Director, Apollo Hospitals, shared the science behind food, fasting and gut health, and explained how people can distinguish evidence-based nutrition advice from the growing noise around the gut microbiome.

Our relationship with food is changing

Dr Anupam Sibal said that modern lifestyles have fundamentally changed the way people eat, with busy schedules increasingly replacing regular meals and family eating routines. He pointed to the growing habit of eating on the move, with even children often having no fixed mealtimes.

“In recent times of course our relationship with food has changed so much, we seem to be in a rush all the time,” he said, adding that people now even take pride in eating on their way to work.

According to Dr Sibal, this shift in eating habits is happening alongside a growing burden of lifestyle-related conditions such as hypertension, diabetes and fatty liver disease. He cited Apollo Hospitals’ annual Health of the Nation survey, which this year analysed 500,000 health records, with the average age of those assessed being 38.

“What did we find? We found that 54 per cent of them had either diabetes or pre-diabetes, 25 per cent of them had hypertension,” he said.

He also highlighted the importance of early intervention, noting that the scope for reversing blood sugar problems was substantially greater when action was taken earlier.

“What is very important is for us to move away from disease and from worrying about how to treat diseases to actually how to look at prevention of diseases and nutrition plays a very very important role.”

Nutrition is not one-size-fits-all

Dr Sibal stressed that the role of nutrition goes beyond simply providing energy, pointing to conditions such as celiac disease to explain how certain foods can have very different effects on different people.

“It’s been known for ages that what is food for one might be poison for the other,” he said.

Using celiac disease as an example, he explained that for people who cannot tolerate gluten, avoiding foods such as roti, bread and pastries can require significant changes to the way the entire family eats. But he emphasised that nutrition is not only about what we eat—it is also about how and when we eat.

“It really is very deep and it’s not just about what we eat and of course that is critical but it’s also how we eat.”

Sibal advised people to eat in a relaxed state rather than multitasking with phones or television. He also highlighted the importance of meal timing and allowing sufficient time between eating and going to sleep.

“You know we need to be in a relaxed state, we don’t need to be multitasking,” he said. “It’s how you eat and it’s also at what time you eat.”

The gut is more than a digestive organ

The gut, Dr Sibal said, does far more than digest food. He explained that it contains its own nervous system – the enteric nervous system – which works closely with the brain through a two-way connection.

“It’s a bi-directional connection,” he said, explaining that stress can produce gastrointestinal symptoms, while gastrointestinal problems can, in turn, contribute to mental stress.

He gave the example of children who experience vomiting or diarrhoea before an examination as a familiar illustration of this gut–brain connection. According to Dr Sibal, the relationship also extends to immunity and other aspects of wellbeing.

“90% of the serotonin production happens in the gut,” he said, while also highlighting the gut’s role in immune function and its barrier against harmful bacteria entering the bloodstream.

Dr Sibal said the gut should therefore not be taken for granted and warned against behaviours that can place unnecessary stress on it, including binge eating and prolonged, unrealistic periods of starvation.

“So it’s extremely important to remember that the gut works tirelessly. Let’s give it the respect that is due to it.”

Good bacteria, probiotics and the microbiome

Dr Sibal said growing research into the gut microbiome has changed how scientists understand the relationship between food and health. He explained that the microbiome begins changing from infancy and is influenced by factors including mode of delivery, breastfeeding and what a person consumes over time.

“There has to be diversity in the gut microbiome,” he said, adding that the balance of microorganisms can influence immunity, mood, allergies and gastrointestinal health.

He pointed to traditional Indian foods such as yoghurt or ‘dahi’ as a simple dietary source of probiotics.

“Dahi is an excellent probiotic, and that is something that each one of us should encourage in terms of consumption every single day.”

However, Dr Sibal cautioned against treating probiotics as a single category of supplements that can address every gut problem. Different probiotic strains have different evidence and uses, he explained, and their effects can vary depending on the condition being treated.

“You just can’t say, ‘Oh, I’m having probiotics, everything’s going to be taken care of.’”

He compared this with vitamins and minerals, where different nutrients have different functions and requirements.

“No, it depends on the species and strain and you have to have the knowledge to be able to give the right probiotic,” he said, emphasising that people should not simply take a supplement because it worked for someone else.

Also read: Food, fasting & gut health: What does the science say?