Your gut:More than just digestion

A bloated stomach at the end of the day, feeling tired more often, or catching colds more easily than you’re used to? You might not think of it straight away, but your gut plays a role in much more than digestion. It’s home to an entire ecosystem: your gut microbiome.

What is the gut microbiome?

The gut microbiome is the community of microorganisms, such as bacteria and yeasts, that live in your gut. Most of them live in your large intestine. There are around 38 trillion bacteria—about as many as there are cells in your own body [1]. These bacteria belong to hundreds of different species, and everyone’s microbiome is different.

What does your gut microbiome do?

A balanced microbiome plays a role in a range of processes.

Digestion and metabolism. Certain gut bacteria break down dietary fiber that we cannot digest ourselves. In the process, they produce short-chain fatty acids, such as butyrate (butyric acid). Butyrate is the main fuel for the cells lining your gut and helps keep them healthy [2].

Your immune system. Your body comes into contact with the outside world through your gut, including with pathogens. That’s why a large proportion of your immune cells are found in and around your gut. Butyrate has an anti-inflammatory effect, and a healthy microbiome helps keep the gut lining and its protective mucus layer intact [2]. What’s more, the more space beneficial bacteria occupy, the less room there is for pathogens.

Your nervous system and your mood. Your gut and brain communicate with each other in both directions through nerves, hormones and the immune system: the gut-brain axis [3]. More than 90% of the serotonin in your body is made in the gut lining, and gut bacteria influence its production [3]. This serotonin doesn’t reach your brain directly, but it shows how closely the gut and brain are connected. In the SMILES study, depressive symptoms improved more among people who switched to a healthier Mediterranean-style diet than among those who received social support alone [4]. The microbiome itself wasn’t measured in that study, and cause and effect have yet to be established. But the findings are promising.

The connection works the other way too: stress can directly affect your digestion. Read more in the blog “Always ‘on’? How stress works in your body.”

How can you keep your gut healthy through diet?

Probiotics: live bacteria. Probiotics are live microorganisms that, in sufficient quantities, provide a health benefit [5]. You can find live bacteria in fermented foods such as yoghurt, kefir, kimchi and unpasteurised sauerkraut. One study found that eating fermented foods daily increased the diversity of the microbiome [6]. Variety is important.

Prebiotics: food for your bacteria. Prebiotics are substances that you do not digest yourself, but that your gut bacteria use as food [7]. They are found in foods such as onions, leeks, garlic, legumes, seeds such as flaxseed, slightly unripe bananas, mushrooms, whole grains and potatoes. The Netherlands Nutrition Centre recommends that adults eat enough fibre each day: at least 25 grams for women and 30 grams for men [8].

Better to limit: ultra-processed foods.  Evidence suggests that ultra-processed products high in sugar, low in fiber and containing certain emulsifiers or additives may negatively affect the microbiome. Much of this research has been done in animals, but there are other reasons to limit these foods too.

What about the salt in fermented foods?

Try sauerkraut. It contains around 1.5 to 2 grams of salt per 100 grams. The recommended maximum is 6 grams of salt per day [8]. If you otherwise eat little salt, it’s perfectly fine to enjoy a serving of sauerkraut now and then. If you use it as a seasoning, a smaller portion is enough: two tablespoons (30 grams) contain about half a gram of salt.

Eat the sauerkraut raw, as heating it kills the bacteria. You can rinse it to reduce the salt content. Some bacteria will rinse away too, but plenty will remain.

What does this mean for you?

A balanced microbiome benefits your health in several ways: digestion and metabolism, immune function, and the nervous system. Research suggests a link between an imbalanced microbiome and a range of symptoms, such as digestive problems, fatigue, and skin issues [source to be added]. This does not mean such symptoms always originate in the gut; there are often other causes too. That's why it's important to take a broad view.

Nutrition can help support your microbiome. If you’d like to understand your situation better, a microbiome test can help us tailor our advice. However, research in this area is still evolving, and there is not yet a consensus on exactly what a “healthy” microbiome looks like. A test is therefore a tool to guide our advice, not a diagnosis.

Want to know what you can do to improve your gut health? Read more about Gut Health and the programme The Balanced Gut, or book a free 15-minute introductory phone call.

Then we’ll discuss together what’s right for you.