The Connection Between the Gut and the Brain: How Does Digestion Affect Our Thinking?

Digestive enzymes work quietly: they break down food into smaller, usable pieces. However, there are certain types of fiber that our own enzymes cannot completely break down—this is where our gut bacteria come into play.

They can produce substances from certain types of fiber that are important for the intestinal wall, the immune system, and gut-brain communication. This doesn’t mean that our gut bacteria “think” for us. Rather, it means that they can influence the internal environment in which our brain functions.

If you’re interested in how you can support all of this with simple, everyday habits, scroll to the bottom of the newsletter.

Enzymes, gut bacteria, and the brain: what does this have to do with thinking?

During digestion, enzymes break down more complex foods into smaller, usable components. We don’t use proteins, fats, and carbohydrates as whole entities, but rather as smaller building blocks. These provide energy, building materials, and many substances that regulate the body’s functions—and, ultimately, the internal state in which our brain operates.

But the story doesn’t end with enzymes. The bacteria living in our gut—the gut microbiome—also play a key role. There are certain types of fiber that we cannot fully break down ourselves, but our gut bacteria can process them using their own enzymes. During fermentation, short-chain fatty acids are also produced, such as butyrate. Research primarily links this to the healthy functioning of the intestinal wall and immune processes.

Why is this interesting from the brain’s perspective?

Because the gut and the brain are not two separate islands. They are in constant communication with each other—this is called the gut-brain axis. This connection can work in several ways: through neural connections, such as the vagus nerve; through the immune system; through hormonal signals; and through substances produced in part by gut bacteria.

Important: this does not mean that our gut bacteria make decisions for us, or that a single food can suddenly make us “smarter.” Rather, it’s about how our diet, the state of our gut, stress, sleep, and exercise together shape the internal environment in which our brain functions. This can affect how stable we feel in terms of our energy levels, mood, attention, and concentration.

How can you support this system in your daily life?

If you’re in good health, one of the best starting points is a varied, fiber-rich diet. You don’t need to worry about complicated rules: eating more vegetables, fruits, legumes, oats, whole grains, seeds, and other plant-based foods is already a step in the right direction. Foods that support butyrate production include, for example, oats, beans, lentils, apples, onions, garlic, slightly underripe bananas, as well as potatoes, rice, or pasta that have been cooked and then cooled.

The key, however, is gradualness. If someone suddenly starts eating a lot of beans, lentils, bran, or psyllium husks, it can easily cause bloating. It’s best to start with small portions and pay attention to how your body reacts.

A few simple habits can also aid digestion:

Eat more slowly than you’re used to. Some bloating and that unpleasant feeling of fullness aren’t necessarily caused by “poor digestion,” but can also result from swallowing air. Eating too quickly, drinking too fast, chewing gum, carbonated beverages, and smoking can all exacerbate this.

Chew your food thoroughly. Chewing is the first step in digestion: it prepares the food for the stomach. If we rush through this or don’t pay enough attention to it, it can make the stomach’s job more difficult in the subsequent stages.

Break large meals into smaller ones. Meals that are too large or too fatty are often harder to digest and can worsen reflux, feelings of fullness, or bloating.

Take a 10–15-minute walk after eating. This isn’t a workout—just light exercise that can help food move through your digestive system.

Don’t lie down immediately after eating. It can be especially helpful for people prone to acid reflux to wait several hours between dinner and bedtime.

Keep a simple food and symptom diary for a week. This isn’t about counting calories. Just write down what you ate, when you ate it, and when you experienced bloating, acid reflux, fatigue, or an uncomfortable feeling in your stomach. Often, this alone is enough to help you notice patterns or identify your individual digestive sensitivities.

Digestion isn’t just chemistry—it’s also a state of the nervous system. Rushing, stress, eating lunch at your desk, or eating in a tense manner can worsen symptoms for many people. Here’s a little trick: before eating, take three slow breaths, sit down properly, and consciously eat the first few bites more slowly.

Finally: it’s fair to say that the more we know about how our bodies work, the clearer it becomes that—despite many similarities—a great many individual factors determine what optimal functioning looks like for each person. That’s why it’s worth paying attention and educating ourselves on the subject. 

When it comes to complex tasks—whether it’s Sudoku, digestion, or health—the secret often isn’t trying to solve everything at once. Rather, it’s about breaking the system down into smaller steps and patiently observing what works.