How does diet affect gut health?

Learn how healthy gut bacteria affect overall wellbeing, the best foods for digestive health, and how antibiotics, sugar and stress can affect the microbiome.

Our digestive system, or ‘gut’ as it is more commonly known, is a complex system comprising of tissues and organs, all with a unique role to play in the digestion and absorption of our food. These include the mouth, oesophagus, stomach, pancreas, gall bladder, liver, and the small and large intestines.

Housed within the gut is also something known as the microbiome: a ‘community’ or ecosystem of microbes (microscopic organisms). These microbes, of which there are about 500 known species, are largely made up of bacteria. Each person carries around 100 trillion microbes within their body, mostly within the digestive tract, although the microbiome can be found in different parts of the body including the nose and mouth. There is emerging research to suggest that it may well influence your health as much as your inherited genes do.

How does the microbiome affect health?

One of the major roles of our gut bacteria, besides digesting our food, is the regulation of our immune system. Recent research has linked the health of our gut to conditions such as acne, allergies and even depression.

There is still lots of research to be done but already scientists have found links between our microbiome (gut bacteria) and neurodegenerative diseases such as Parkinson’s, as well as the long-term condition chronic fatigue syndrome. There is also growing evidence around the role of our microbiome in obesity and weight management, as well as autoimmune conditions such as Type 1 diabetesand rheumatoid arthritis.

Woman standing on weighing scales in bathroom

Why is the gut considered to be the ‘second brain’?

Your digestive system is also known as the ‘second brain’ thanks to the millions of neurons that line the gut and release important chemical messengers known as neurochemicals or neurotransmitters. These allow the gut to keep in close contact with the brain and influence our moods and emotions.

Our gut bacteria play a key role in the production of certain neurotransmitters, such as serotonin, which is manufactured in the gut and known as our ‘happy hormone’.

What can affect gut bacteria?

Just like fingerprints, every one of us has a different microbiome, and this can be influenced by a wide variety of factors, including the mode of delivery at birth, the method of infant feeding, the use of medications (especially antibiotics) and the diet. The most common culprits that can affect gut bacteria include antibiotics and a diet low in fibre, fruit and vegetables. Antibiotics are used to treat or prevent some types of bacterial infection by killing bacteria in the body. While they are an important medicine, they cannot distinguish between good and bad bacteria, so they wipe out both.

Stress can change the number and diversity of our gut bacteria, which in turn dysregulates the immune system and may explain why certain conditions, such as eczema or acne, flare up when we are more stressed.

How can I improve my gut microbiome?

The good news is that there are plenty of things you can do to look after your digestive system and support a healthy microbiome. Start by looking at your diet and increase the amount of fibre, fruit and vegetables that you eat, as these are really good sources of soluble fibre which are very important for ‘feeding’ the good bacteria. Other high-fibre foods include beans and pulses, such as chickpeas and lentils, wholegrain breads, brown or wholegrain rice, nuts and seeds, oats and jacket potatoes. Fermented foods, such as sauerkraut, kimchi and kefir, are increasing in popularity too thanks to their gut-friendly benefits.

If your GP has prescribed a course of antibiotics, it’s important to follow them as directed. However, as per NHS advice, you should only take antibiotics when necessary. If you are concerned that antibiotics may have a negative effect on your gut bacteria, ask your GP about following them with a course of probiotics, which may help to reset the balance of bacteria.

Activities such as mindfulness or meditation can help you to relax and reduce your stress levels so that they don’t have such an impact on your digestive system

BBC Future: What we do and don’t know about gut health