“You are what you eat.” It’s a common saying, but when it comes to your health – especially your gut health – what you eat has a profound impact on keeping you in good shape and new evidence shows that the bacteria in our gut also interacts with our immune system.
Whilst we are still learning what a healthy gut microbiome looks like, evidence suggests that a balanced and diverse microbiome might contribute to better health overall, and a less diverse or less balanced microbiome can have a negative impact on health.
From what we know, the best way to establish and maintain a healthy gut microbiome is to get enough sleep, regular exercise and eat a varied, balanced diet. The food you eat has a big impact on the range and type of microbes in the gut, and here we explain.
Food for your gut bugs
With 100 trillion bacterial cells in our gut, that’s a lot of mouths to feed! The different strains of bacteria in our gut can change drastically depending on the types of food eaten. Of all foods, fibre is especially important as this is their key fuel. Particular types of fibre, called prebiotics, are especially important as these fuel the growth of particular groups of the beneficial bacteria, such as Bifidobacteria and Lactobacillus.
Some of the benefits of feeding your healthy gut bacteria include improving the functioning of the gut wall, keeping bowel movements regular and improved immunity. What’s more, by providing plenty of prebiotics for the beneficial bacteria to ferment, you help reduce the amount of potentially-damaging gut bacteria.
These benefits are principally brought about by the fermentation process. When the bacteria ferment the fibres, they produce a group of compounds called short chain fatty acids. These increase the acidity in the bowel, making it harder for potentially harmful bacteria to thrive. The fatty acids also keep the cells of the gut lining healthy and help us to absorb more nutrients from our food, such as calcium and magnesium.
What to eat for a healthy gut
To keep your gut environment thriving, aim to eat more foods high in different types of fibre including soluble fibre, insoluble fibre and resistant starch. Fibre can be found in an array of everyday foods.
Some of the key prebiotic foods include:
- Aromatic vegetables such as onions, garlic, leeks, celery and Jerusalem artichokes. These are high in a type of carbohydrate called inulin which bacteria use to promote healthy colon cells and other health benefits.
- Barley and oats are a rich source of the soluble fibre, beta-glucan. Beta-glucan acts as food for your good gut bacteria and helps lower cholesterol levels.
- Starchy foods such as cooked and cooled potatoes, beans, lentils, and firm bananas are a great source of resistant starch to fuel good gut bacteria.
- Fermented foods such as sauerkraut, kimchi, kefir and yoghurt contain a good supply of healthy bacteria to add to your own, along with products of fermentation that may boost gut health.
While researchers have yet to work out what the ‘perfect’ diet may be for gut health, we already know that the worst way of eating for your digestive health is consuming too many highly processed foods, too much sugar and not enough fibre. The good news is that a shift to a healthier diet can change the bacteria mix in just a few short days.
A recent study involving African Americans who swapped their meat-heavy, highly processed diet for a diet typical of African foods rich in beans and vegetables saw a positive change in gut bacteria within just two weeks. And the reverse swap saw that when rural Africans switched to a typical American diet, their microbe profile was more in line with one known to be associated with a higher risk of colon cancer.
Two weeks is a short time, but long enough to make changes to the microbe population that can reduce your risk of disease. To make these changes permanent, you have to keep up your new healthier diet; revert back to your previous way of eating, and your gut bugs will revert back to their previous profile.
The fine details of the interactions between the gut microbiome and immune system are not fully understood. But by sticking to better food choices you’ll reap the benefits of a healthier, more balanced and diverse range of gut microbes. To do this, approach it as a long-term game – make small changes and healthy food swaps over many weeks to make the healthier diet sustainable. Something as simple as eating two pieces of fruit each day and opting for whole grain foods over refined grains is a great way to start. Then look at adding in more prebiotic foods to vary your diet. Remember, healthy eating isn’t only to keep your stomach happy – your own unique collection of gut bacteria will thank you, too.
- Belkind Y, Hand T. Role of the microbiota in immunity and inflammation. J Cell. 2014;157(1):121-141.
- Bird AR, Conlon MA. The impact of diet and lifestyle on gut microbiota and human health. Nutrients. 2015;7(1):17-44.