Gut health is an important aspect of our overall health and wellbeing. Emerging research suggests a link with many other aspects of health, such as immunity, mental wellness and preventing some illnesses.
In this section, we explore…
The term ‘gut’ is used in many ways. It’s sometimes used to describe the stomach or belly. It may also be used to explain an instinctive reaction such as a ‘gut feeling’ or an emotional response like ‘feeling gutted’.
Medically, however, the gut refers to the digestive system – a long tube that breaks down food and drink into energy, nutrients and water, which keep our body functioning and healthy.
The journey begins in the mouth. Here, chewing breaks down food and mixes it with saliva, which contains digestive enzymes. Then it moves through the oesophagus into the stomach where digestion continues.
Next, food enters the small intestine for the final stages of digestion. Nutrients are then absorbed into the blood.
Any undigested parts of food such as fibre and some starches that resist digestion (resistant starch) pass into the large intestine. This section of the digestive system absorbs water. It also contains more than 100 trillion microbes, tiny microorganisms like bacteria, viruses and fungi that can only be seen under a microscope. These microbes feed on the undigested material breaking it down further. The remaining waste then leaves the body through the anus as faeces (poo) when we go to the toilet.
While the term ‘gut’ technically covers the entire digestive system, it’s often used to refer to just the large intestine.
In the past few decades, scientists have found the microbes living in our large intestine may help keep us healthy. These microbes are mainly made up of bacteria, with some viruses and fungi. Collectively, they are known as the gut microbiota. The environment they live in – the large intestine – is called the gut microbiome.
It’s thought around 3,000 species of bacteria may potentially be present in the gut, though only 100-150 species live there at any one time. With so many different species and possible combinations of bacteria, everyone’s gut microbiota is unique. There’s no perfect or ideal composition. It’s the diversity and balance of beneficial or good bacteria that’s seems to be important for a healthy gut microbiota. If this balance is upset though, research suggests our health could suffer in various ways.
The microbes in our gut have many important roles…
As well as looking after the microbes living in our gut, a healthy diet helps support regular bowel movements and prevents problems such as constipation.
A good starting point for eating healthily is to follow The Eatwell Guide. This shows the types and proportions of foods to eat for a balanced, nutritious and sustainable diet.
There are two parts of a healthy diet that are particularly important for keeping the gut healthy…
A plant-rich diet (also sometimes called a plant-based diet) is one where plenty of different plant foods are included but can also include some animal foods such as meat, fish and dairy.
Plant foods such as vegetables, fruits, beans, lentils, chickpeas, nuts, seeds, and wholegrains benefit gut health because they add fibre to diets.
There are many types of fibre. The one thing they all have in common is they’re not digested, so they end up in the large intestine.
Once here, some types of fibre provide food for beneficial gut bacteria, supporting their growth. These types of fibre are called prebiotics. They’re found in onions, garlic, leeks, artichoke, chicory root, asparagus, bananas, apples, berries, wheat, oats, beans, lentils and chickpeas.
Other types of fibre have different functions. For example, some fibres add bulk to stools so they’re softer and easier to pass, while some bind with other substances to help control blood sugar and lower cholesterol.
The many different functions of fibre help to explain why good intakes are linked to a lower risk of many diseases, including constipation, bowel cancer, heart disease, stroke, and type 2 diabetes.
Studies have looked at how the Mediterranean diet can affect our gut bacteria and found that following this dietary pattern is linked to increased levels of beneficial bacterial strains and increased production of short-chain fatty acids that can have health benefits.
Fibres found in whole grains influence gut transit rate and bacterial fermentation. Two trials with people who were overweight or at risk of developing metabolic syndrome found that a whole-grain diet increased levels of beneficial compounds produced by gut bacteria, improved blood lipid profiles (such as blood cholesterol), reduced inflammation and improved weight loss compared to a refined grain diet.
On the other hand, research has found that a typical western diet, low fibre and fruit and vegetable is linked to less diversity in the gut microbiome compared to other diets, with a shift towards fewer beneficial types of bacteria.
Eating a variety of plants adds different types of fibre to diets. Here’s how to enjoy more…
11. Stock up on frozen and canned veg – just as nutritious as fresh and ideal for speedy meals.
12. Enjoy meat-free meals – turn favourites such as lasagne, risotto and stir fries into veggie versions.
13. Snack on veg – serve carrot sticks, pepper slices and cauliflower florets with hummus or guacamole, have a bowl of veg or bean soup, or top rye crackers with avocado and tomatoes.
14. Give shop-bought ingredients a plant boost…
15. Add veg to bakes – look online for recipe inspiration such as adding black beans to brownies, courgette to muffins, or beetroot to cakes.
16. Enjoy nuts and seeds – stick to a small handful (around 20g), choose unsalted, and vary choices to get a good mix of nutrients.
17. Go for veg variety with staples…
Eating a variety of plants provides different combinations of fibre, vitamins, minerals and phytochemicals that support overall health.
The idea of eating 30 plants a week gained attention after a study found people who consumed at least 30 plants a week had a more diverse range of bacteria in their gut than those who ate 10 or fewer plants.
Trying new grains, experimenting with different fruit and veg, and enjoying more pulses, nuts, seeds and soya can help expand the nutrients we get and add variety to meals. See the ideas above for adding more plants to our diet.
However, 30 plants a week is not an official health recommendation in the UK and there’s much less evidence for this approach than there is for the 5 A DAY recommendation. The NHS recommends eating at least five portions of different fruit and veg daily. To help increase variety, eat a rainbow of different colours each day.
Water is essential for our digestive system. It helps nutrients to be digested and absorbed. It acts as a lubricant to help food move through the digestive tract. In the large intestine, water softens the stools so they’re easier to pass. Without enough water, stools can become hard and dry. This is why a lack of fluid can contribute to constipation.
To stay hydrated, a general guide is to drink 6-8 glasses of fluids a day. The exact amount we need depends on our body size, gender, age, and how much we sweat, which can be influenced by exercising, hot weather, menopausal flushes or having a fever. Breastfeeding, medications with a diuretic effect, and illnesses that cause diarrhoea, sickness or increased urination (such as uncontrolled diabetes), also mean the body loses fluid, which need replacing.
Checking our urine is the best way to tell if we are hydrated. While some foods, medicines and supplements can affect the colour, urine that’s pale and odourless generally means we are hydrated. Dark urine with a strong odour indicates we need to drink more.
Feeling thirsty is a sign of dehydration, so it’s especially important to drink. All fluids (except alcohol) count towards fluid needs.
Find more in our article on healthy hydration.
What are probiotics and which foods contain them?
Probiotics are sometimes described as ‘good’ or ‘friendly’ bacteria that help to support a healthy balance of bacteria in the large intestine or gut.
Foods that contain probiotics include yogurt and fermented milk drinks. Probiotics are also available in supplements as tablets, sachets or capsules.
On ingredients lists, probiotics are labelled with the specific bacteria they contain such as Lactobacillus casei (L.casei) or Bifidobacterium lactis (B.lactis).
Prebiotics are types of fibre that provide food for beneficial bacteria in the gut, helping them thrive. Foods rich in prebiotics include:
Prebiotics are also added to some foods and supplements. Examples of prebiotics that appear in ingredients lists include chicory fibre, inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GOS).
What’s the difference between prebiotics and probiotics?
Prebiotics and probiotics work together to support gut health. Prebiotics provide food for the beneficial bacteria in the gut, while probiotics are the beneficial bacteria.
How do probiotic foods, drinks or supplements benefit health?
It’s difficult to measure whether probiotics can make you ‘healthier’ overall but they may help manage some specific conditions. Potential benefits supported by evidence include:
Probiotics vary in their effects and choosing the right strain for a condition is important. A registered dietitian can help with this.
Meanwhile, the NHS advises anyone with a health condition or weakened immunity should consult a doctor before using probiotic supplements.
The British Dietetic Association and NHS have more information about probiotics.
Will eating fermented foods benefit my gut health?
Fermented foods such as yogurt, sauerkraut, kefir, kimchi, tempeh, miso and kombucha may contain live bacteria and are often promoted as being beneficial for gut health. However, these foods are not always considered to be true probiotics as the types and amounts of microorganisms they contain are not consistent and evidence of their health benefits is often limited.
It’s not always easy to tell if fermented foods contain any live microorganisms. For example, some fermented foods such as sourdough bread or jars of sauerkraut may not contain live microbes due to high temperatures during processing. Look for labels stating ‘contains live or active cultures’ to identify foods with live microorganisms.
Fermented foods can still be enjoyed as part of a balanced, varied diet, but it’s important to check labels for salt and sugar content as some products may be high in these.
Are sweeteners bad for gut health?
At present, studies looking at links between sweeteners and gut bacteria have produced mixed results. Some suggest they have a minimal effect, while others indicate they may upset the balance of gut microbes. More research is needed before any firm conclusions can be made. But if you prefer to avoid sweeteners, check the labels on products like drinks and yogurts.
It’s worth noting sweeteners are just one aspect of diet that may influence the gut microbiota. Eating a healthy, plant-rich diet remains one of the best ways to support gut health.
Should I avoid UPFs to keep my gut healthy?
Studies suggest a link between high intakes of ultra-processed food (UPF) and poorer gut health but there’s not enough evidence to say UPFs directly disrupt the balance of gut bacteria.
More research is needed to see if and how the level of processing affects gut microbes. Similarly, though some studies have suggested food additives such as emulsifiers or sweeteners may affect the gut microbiome, far more research is needed before any firm conclusions can be made.
It’s worth noting that diets high in UPFs are often lower in fibre, a nutrient that’s known to support a healthy gut microbiome. Eating a plant-rich diet that’s high in fibre is one of the best ways to support a healthy gut.
Synbiotics are combinations of prebiotics and probiotics that work together or in synergy to support gut health. The probiotic part increases beneficial gut bacteria, while the prebiotic part helps to feed these beneficial bacteria. Synbiotics are usually available in supplement form.
