Gut Health: A Practical, Science-Backed Guide

Gut health is everywhere right now, from kefir in the supermarket to influencers selling expensive tests. Strip away the hype and the advice that holds up is refreshingly simple: eat more fibre, eat a wider variety of plants and add some fermented foods. Here is what the research says and how to put it into practice.

What is your gut microbiome?

Your gut microbiome is the community of bacteria and other microbes living in your digestive system, mostly in your large intestine. You may have heard that bacteria outnumber your own cells ten to one. A 2016 recount put the figure at roughly 40 trillion bacteria, which is about the same as the number of human cells in your body.

These microbes do jobs your body cannot do on its own. Among the most important, they ferment the fibre you cannot digest and turn it into compounds called short-chain fatty acids, which are one of the ways your gut bacteria communicate with the rest of your body.

The gut-brain connection

Your gut and brain are in constant two-way contact. A major review describes several routes for this: the vagus nerve, the immune system, the nervous system in your gut wall and chemicals made by your gut bacteria, including short-chain fatty acids. Researchers are studying how this link affects mood, stress and brain health.

It is an exciting field, but much of the strongest evidence still comes from animal studies, and human research is ongoing. Be wary of anyone selling a product that promises to fix your mood through your gut.

Gut health and training

Exercise and gut bacteria do seem to be linked. One study found that players in an international rugby squad had more diverse gut bacteria than a comparison group, and that diversity was linked to how much protein they ate. The researchers pointed out that the athletes' training and their diets went hand in hand, so it is hard to separate the two.

The practical takeaway is reassuring: the habits that support your training, such as regular exercise and a varied diet with plenty of plants and enough protein, are the same habits your gut bacteria do well on.

Fibre: what your gut bacteria eat

Fibre is the single biggest thing you can change. The NHS recommends adults eat 30 g of fibre a day, but the average adult in the UK manages only about 20 g. Eating plenty of fibre is linked to a lower risk of heart disease, stroke, type 2 diabetes and bowel cancer, and it helps prevent constipation.

• Switch to wholemeal bread, wholewheat pasta and brown rice.
• Have porridge or a higher-fibre cereal for breakfast.
• Leave the skins on your potatoes.
• Add beans, lentils or chickpeas to stews, curries and salads.
• Snack on fruit, vegetable sticks, oatcakes or a handful of unsalted nuts.

If you eat very little fibre now, increase it over a couple of weeks rather than overnight, and drink plenty of fluids. Going from 15 g to 40 g in a day is a quick route to bloating. Our guide to fibermaxxing goes deeper.

Aim for 30 different plants a week

Variety matters as well as quantity. In the American Gut Project, a large study of people mostly from the US and UK, those who ate 30 or more different plants a week had more diverse gut bacteria than those who ate fewer than 10. It was based on what people reported eating, so it shows a link rather than proof, but it is an easy and useful target.

Every fruit, vegetable, wholegrain, bean, lentil, nut, seed, herb and spice counts. A few easy ways to rack them up:

• Buy mixed bags: frozen mixed vegetables, mixed beans, mixed seeds or a mixed salad.
• Top porridge or yoghurt with berries and a spoonful of mixed seeds.
• Add a tin of mixed beans or lentils to mince, chilli or soup.
• Cook with herbs and spices. They count too.

Fermented foods

Fermented foods contain live microbes or the products they make. In a randomised trial, healthy adults were asked to eat either a diet high in fibre or a diet high in fermented foods. The fermented food group saw their gut bacteria diversity rise steadily and their markers of inflammation fall. In the high-fibre group, diversity stayed about the same over the study period.

Good options to try:

• Natural yoghurt or skyr with live cultures
• Kefir, a fermented milk drink
• Sauerkraut and kimchi
• Miso, tempeh and kombucha

Pick unsweetened versions where you can, and start with a small portion if you are not used to them.

Do you need probiotic supplements?

For most people, no. The NHS describes probiotics as live bacteria and yeasts promoted for their health benefits, and says there is little evidence to support many of the claims made about them, although there is some evidence they may help in some cases.

Because probiotics are generally classed as food rather than medicine, there is no guarantee a product contains the bacteria it lists, in a useful amount, or that they survive the trip to your gut. They appear to be safe for most people, but if you have a weakened immune system or a health condition, speak to your doctor first.

When to see a GP

A simple plan to start this week

1. 1

   Add one more portion of fibre a day

   An extra portion of vegetables, a tin of beans or a switch to wholegrain is a good start.
2. 2

   Count your plants

   Keep a tally for one week and see how close you get to 30.
3. 3

   Have one fermented food a day

   A pot of live yoghurt or a glass of kefir is the easiest option.
4. 4

   Keep training and sleeping well

   Regular exercise and good sleep support your health in ways no supplement can.

The free BarbellBites app tracks fibre alongside your calories and protein, so you can see how close you are to 30 g without doing any maths.

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