Did you know that humans are made up of more bacteria than cells, with scientists estimating that around 100 trillion bacteria live in our digestive system alone?

These tiny microbes – known as the gut microbiota – play an essential role in our everyday health and help govern nearly every function of the human body. Studies have indicated that having a large variety of thriving bacteria in our gut microbiome can help to reduce the risk of major health conditions, including IBS, diabetes, arthritis, depression and anxiety.

Improving your gut health with expensive probiotic supplements is now a mainstream concept – but how can you tell if you have a problem in the first place? To help us identify the subtle signs of an unhealthy gut, we asked Nigel Denby, dietician and founder of Harley Street at Home, to give us the lowdown.

What are the signs of an unhealthy gut?

The key to good gut health is maintaining a balance between the good and bad bacteria in the microbiome. If your gut is acting differently than usual, it could be a sign of an imbalance — and there are some obvious clues that things may be out of whack.

“Look out for the symptoms of irritable bowel syndrome, which is essentially an issue in the gut that doesn’t have any obvious cause,” says Denby. “For a diagnosis of IBS, NICE (The National Institute of Health and Excellence) guidelines look for three of the following: recurrent bloating, abdominal pain and discomfort, changes in bowel habit (where you become more constipated, more loose and urgent, or fluctuate between the two), gas and mucus in the stools.”

An upset tummy after a dodgy takeaway isn’t usually a cause for concern, but recurrent symptoms can indicate that your microbiome needs some attention. “Keep a diary over three or four weeks so you can notice any trends,” says Denby. “It doesn’t necessarily have to be every day, but you might notice these issues cropping up regularly over time.”

What might cause someone to have an unhealthy gut?

One of the main reasons an imbalance of ‘bad’ bacterial strains can thrive in the gut is that there simply aren’t enough good bacteria to keep them in check.

“The gut microbiome is made up of billions of single-cell organisms that have created a little ecosystem inside your large intestine,” Denby explains. “They work together to carry out millions of different tasks like absorption of nutrients, packaging waste, and getting rid of it through the colon.”

Denby suggests considering your microbiome a “great big metropolitan city”. As long as your bacteria are in harmony, everything works as it should. “If the bad bacteria outweighs the good, the traffic lights break down, and you’re in anarchy. The ‘bad’ organisms keep replicating themselves, and the species that are depleted in numbers can’t recover and do their job,” he explains.

Many facets of modern life can deplete good bacteria and cause an overgrowth of certain strains. “Antibiotics, stress, alcohol consumption, lack of sleep, eating processed foods, physical trauma around the abdomen and bouts of food poisoning can give your microbiome a kicking,” warns Denby. “Perhaps you did a lot of partying at university, travelled the world, had a C-section birth and have been under long-term stress through redundancy, divorce or bereavement? All of these aspects can impact the gut flora.”

What can you do to improve your gut health?

When it comes to having a happy and healthy gut, many people jump straight into excluding the foods they think might be causing issues, but Denby says it’s really a question of building balance and diversity.

“The first thing I recommend is taking a good quality probiotic for about three months to see if it helps,” he notes. A general recommendation is to choose probiotic products with at least 1 billion colony-forming units and containing the genus Lactobacillus, Bifidobacterium, Bacillus or Saccharomyces boulardii.

Long-term stress is another key consideration. For some people, stress slows down digestion, causing bloating, pain and constipation, while in others, it speeds it up, causing diarrhoea and frequent trips to the toilet. As Denby explains: “Stress can cause the muscles in the large intestine to lock. If you send all your stress to your tummy, those muscles can lock, and you get a bit of backup constipation. When they eventually relax, you’ve got urgency and diarrhoea.”

Gentle, abdominal muscle massage at nighttime can help the muscles to relax. “These techniques can help you get rid of the trapped gas overnight, and wake up in the morning ready to empty your bowels and get on with your day,” Denby says.

A diet high in processed foods and added sugars can also decrease the number of good bacteria in your gut. “Most of us don’t eat enough fibre,” stresses Denby, “so you need to look at what you’re loading on your plate.”

He advises we opt for a large variety of whole foods, rainbow-coloured vegetables, legumes and fermented foods to encourage gut diversity. “We should aim for 30 different types of plant-based foods each week, but you need to increase your water intake too. It’s all well and good eating more dietary fibre but you need six to eight glasses of water per day to get the benefit and help avoid constipation.”

If you’re still encountering problems after limiting stress, getting good quality sleep, improving your diet and taking a probiotic, you may want to try a low FODMAP diet. Gut issues can be caused by an intolerance to certain foods, particularly those high in FODMAPS — carbohydrates that are found in certain foods like wheat and beans, that the body finds difficult to break down.

The low-FODMAP diet is a temporary eating plan with three clear stages. “In the first phase, you eliminate high FODMAP foods (which include garlic, onion, baked beans and rye) for four to eight weeks,” says Denby. “Next, you introduce each food carefully in isolation over three days, monitoring your symptoms.”

Once you identify the foods that cause symptoms, you can avoid or limit them while enjoying everything else worry-free. “It might be that you can take some foods in small doses but can’t eat them regularly,” says Denby. “Working with a professional dietician is useful as you can work out a personalised plan that avoids triggering your gut.”

Finally, it can be helpful to consult with your GP if you’re worried about your gut health, as while there’s no test for IBS, you might need some tests to rule out other possible underlying causes of your symptoms. If your doctor thinks you have IBS, they’ll talk to you about your symptoms and the treatment options available.