Trust your gut! No, seriously, trust. Your. Gut. Gut health is a hot topic; people are discussing how to eat gut-healthy foods to strengthen the microbiome. The microbiome includes over a trillion of the naturally occurring microbes, such as bacteria, that live inside our bodies, particularly in the gut.¹ The gut is also a lot more than just the stomach. The gastrointestinal (GI) tract or digestive tract includes the oesophagus, small intestine, large intestine, and anus.² A lot of recent research has gone into showing the dramatic effect that the microbiome has on general health, and people have begun to prioritise strengthening their microbiome as a result. This article aims to detail the proven ways to nourish your microbiome: eating a balanced diet. 

The role of the microbiome

Unsurprisingly, the microbiome fulfills such a large role in the body seeing as there are as many microbes as there are human cells in the body. The microbiome includes all microorganisms that inhabit the human body, such as bacteria, fungi, and viruses. Although a large number are found in the gut, microbes are also present on the skin, in the respiratory tract and vaginal tract.³ Many people associate microbes, or germs, as harmful, but in reality, millions of “good” microbes are essential for health. 

The microbiome plays many roles, including extracting nutrients from food eaten for digestion. Through this important role, the microbiome's health greatly impacts weight stability and general bodily nourishment. More surprisingly, the microbiome also plays a large role in immunity by protecting the body against disease-causing microbes called pathogens.⁴ Moreover, the microbiome has been shown to play a large role in influencing mental health. This is due to its role in the gut-brain axis, a bidirectional communication network that relies on the exchange of signals between the microbiome and the brain. Several mood disorders, such as anxiety and depression, have been associated with GI tract disruptions.⁵ 

How diet impacts the microbiome

Diet plays a critical role in determining the microbiome's health by directly affecting its composition and diversity. A nutritionally balanced diet promotes a healthy gut and eating at least 30 different types of plant foods a week was shown to create a diverse and strong microbiome.⁶ Conversely, processed foods, which are often high in sugar and fat, such as common in the typical Western diet, have been shown to impact the flora of the gut negatively and have even been associated with the development of Leaky Gut Syndrome.⁷

These harmful alterations to the gut’s microbiome from an unhealthy diet can cause dysbiosis by reducing microbiome diversity, reducing beneficial microbiota, or increasing harmful microbiota.⁸ Moreover, highly processed foods often have additives such as sweeteners and emulsifiers, which have been shown to weaken the gut, increasing inflammation and permeability. Overall, overconsumption of highly processed foods with low nutrition profiles can rapidly alter the gut microbiome in a way that promotes diseases such as diabetes, cancer and obesity.⁹

Foods that nourish the microbiome

Probiotic-rich foods

Probiotics are commonly known as “healthy” bacteria and are often prescribed as a supplement alongside antibiotics, depleting the body's bacteria reserves. However, a lot of foods also naturally contain these healthy microbiota.¹⁰ Fermented foods are rich in live probiotic bacteria and have many health benefits, including nourishing the microbiome. Fermented foods such as kefir yoghurt which contains live cultures of bacteria, pickled vegetables, kimchi, and tempeh are recommended for daily consumption to promote a healthy gut.¹¹ Moreover, the addition of probiotic-rich foods has also been associated with decreased risk of heart disease, arthritis, cancer, depression and general GI tract diseases.

Prebiotic-rich foods

The health benefits of prebiotics are often overlooked as they are classified as substances that cannot be fully digested by the intestines such as some starches found in high-fiber foods. However, prebiotics work in tandem with probiotics and function to feed the healthy microbiota and allow them to flourish. The probiotic microbes ferment these indigestible prebiotic compounds and use them for energy to thrive.¹² Therefore, consuming plenty of prebiotic-rich foods is recommended to aid the survival of this beneficial bacteria. Some prebiotic-rich foods include asparagus, onion, garlic, artichokes, leeks, bananas, and whole grains. 

Fiber-rich foods

High-fiber foods are those that are rich in plant-based carbohydrates. These foods themselves, which prebiotics help to digest, also play a fundamental role in strengthening the gut and ensuring adequate movement of food through the gut. Aided by prebiotics, dietary fiber is fermented in the gut and is beneficial in producing microbiota metabolites such as short-chain fatty acids which allow beneficial bacteria to grow and thrive.¹³ While the recommended daily fiber intake is 20-35 grams, the global average ranges from15-26 grams. Some foods recommended for consumption to boost your fiber intake are legumes, chia seeds, oats, berries, and almonds. Generally, fiber levels can be increased by choosing wholemeal or granary bread, consuming a fiber-rich breakfast such as Weetbix, and adding a variety of different vegetables to eat meal.¹⁴

Why variety is the key to gut health

If you were to construct one perfectly balanced meal and commit to eating that meal 3 times a day, you would actually be doing your gut a disservice. Although that meal may be healthy, our guts thrive off of variation, and increasing the diversity of our diets is key to strengthening the gut microbiome. The more different kinds of food eaten, the more the gut is exposed to varying nutrients and adapts to be able to digest them all. This variation also equips the gut to be able to combat disease when it arises more effectively. The way to achieve this variation is by experimenting with new recipes that incorporate new fruits and plants into your diet regularly.¹⁵

Other factors affecting the microbiome

Lifestyle factors

Although having a balanced diet is crucial for gut health, other lifestyle factors such as sleep, stress, and exercise can affect the microbiome. Regular exercise has been shown to affect gut-brain access and result in lower inflammation in the gut. Exercising and keeping a healthy lifestyle also has a knock-on effect on getting adequate sleep and reducing stress levels.¹⁶ High stress levels are associated with an increase in gut permeability and a decrease in the efficiency of beneficial bacteria in the gut. Managing stress is therefore also key to maintaining a strong flora in the gut.¹⁷

Antibiotics and the microbiome

Antibiotics function to attack and kill harmful bacteria that are causing a bacterial infection in the host. However, they are not specific and end up killing a lot of beneficial bacteria in this process. This greatly reduces the diversity of the microbiome as a result. This medication is sometimes necessary and unavoidable to combat disease but these negative side effects can be somewhat lessened through taking a prescribed probiotic alongside the antibiotic that will help to reintroduce healthy bacteria.¹⁸ Although probiotic supplements can be beneficial in this situation and for treating other diseases such as Irritable Bowel Syndrome (IBS), they are not generally recommended for general consumption to promote a healthy gut. A balanced and diverse diet is more than effective on its own to promote gut health with out the use of supplements and medical professionals should always be consulted before considering adding a supplement to your diet.¹⁹

Summary

The microbiome of the gut refers to all of the microorganisms that live within the digestive tract. These microorganisms play a crucial role in digestive health, immunity and mental health. Maintaining a diverse microbiome with a variety of beneficial bacteria and microbes is essential to achieve these benefits. A diverse microbiome can be achieved by eating a healthy and balanced diet that is rich in probiotics, prebiotics and fiber. Generally, the easiest rule to follow to benefit your gut health is to prioritize incorporating large numbers of different types of fruits and vegetables each week. This variety strengthens the responsibility of the gut microbiome and effectively prepares the gut to be able to combat diseases and digest all food efficiently.