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Plant-Based Diets and Gut Health

Eating more plant fibres can help improve your gut microbiota diversity and protect your intestinal barrier while preventing the growth of pathogenic bacteria and cancerous cell growth. But how exactly?

The gut microbiota consists of microorganisms living in your digestive system, mainly in the colon. Most of these microorganisms are not harmful and, in fact, are beneficial to our health. These microorganisms are highly impacted by our diet. Eating a diet rich in fibre from fruits, vegetables, whole grains, and legumes is necessary to ensure a healthy gut and a happy microbiota.

How does our diet impact our gut microbiota?

A strong and healthy gut microbiota is important for digestive health, immunity against harmful pathogens and can even impact your mood!¹ So, how can a plant-based diet help you maintain a healthy gut? Well, the beneficial bacteria in your gut microbiota ferment fibre to feed themselves. These ‘good’ microorganisms take up space and resources in your gut, making it hard for disease-causing (pathogenic) bacteria to survive. This means a fibre-rich diet filled with fruits, vegetables, whole grains, and legumes can be very beneficial for your microbiota. 

4 ways a plant-based diet can improve your gut health:

1. Prevent growth of pathogenic bacteria 

Modern diets high in sugar and low in fibre drive the growth of harmful microorganisms in the gut. When a gut environment has excessive sugars available as nutrients, it can increase the presence of pathogens that feed on them and make gut microbes more harmful, which can cause inflammation. Long-term inflammation is common in diseases such as diabetes and obesity, which are often related to a Western pattern of diet in which simple carbohydrates and red meat intake is high and consumption of vegetables and fruit is low.²,³

Diets rich in fibre, however, allow your beneficial bacteria to ferment that dietary fibre and grow, making the intestinal environment more acidic in the process. The acidic environment also makes it harder for harmful bacteria to grow, as they are ill-suited to acidic conditions - tipping the balance in favour of beneficial bacteria, benefiting your overall gut health. Favouring a balanced plant-based diet high in fibre can, therefore, enrich populations of beneficial bacteria in our gut instead of encouraging those that cause disease.

2. Improve gut microbiota diversity

A balanced plant-based diet rich in different kinds of vegetables can also increase the healthy microorganism diversity of your microbiota. This occurs because different types of plant-based foods have different types of fibre in them and can, therefore, feed a range of different beneficial microorganisms. Fibre supplementation has a similar effect in this regard. In contrast, diets consisting of lots of refined sugars and saturated fat with low consumption of whole fruits and vegetables have been shown to contribute to lower microbiota diversity - such lower diversity has also been associated with certain diseases such as obesity and diabetes,, and has also been related to anxiety, depression, schizophrenia and autism.¹ Some studies have shown reduced anxiety and depressive symptoms in those who have been treated with probiotics (beneficial bacteria).¹   

3. Protecting the gut wall

Our intestine has a thin layer of cells called the ‘intestinal barrier’, which protects us from things that should not be entering our body (such as toxic compounds or harmful bacteria and viruses) while allowing nutrients to pass from the gut to the blood circulation for distribution around the body. A disruption to the gut barrier makes it easier for harmful compounds to enter the bloodstream, putting our health at risk. 

This disruption of the gut barrier can be triggered by sustained unhealthy eating habits involving regular ultra-processed foods, as fats and certain additives from these products can increase gut permeability and trigger an inflammatory immune response. Although inflammation is a natural response of the body, sustained inflammation can eventually harm our cells, leading to further damage to the intestinal barrier.

However, a diet high in fibre from minimally processed foods can help protect the gut wall. When beneficial bacteria ferment fibre, the process produces short-chain fatty acids (SCFAs). These fatty acids provide energy for your gut cells, thereby supporting your gut barrier and preventing harmful gut bacteria and toxic compounds from entering the bloodstream, where they are likely to cause disease. 

4. Inhibit cancer growth 

Diets high in fibre can help prevent cancerous cell growth in the intestine. Firstly, the SCFAs produced through fibre fermentation can inhibit cancerous cell formation and can even lead to the death of cancerous cells. Secondly, as fibre is largely indigestible by our own cells, it can help us with our bowel movement, clearing waste from our gut. Fibre can also bind to certain heavy metals that may be in contact with our intestinal cell wall and help excrete them from the body. Some strains of lactic acid-producing bacteria have also been shown to capture heavy metals, reducing the health hazard of such elements in the gut.¹⁰ Because these beneficial strains feed on soluble fibre, lactic acid-producing bacteria increase their numbers in our gut when we regularly consume foods such as legumes, oats and certain fruits.

Eating a variety of fruits, vegetables, whole grains, and legumes and avoiding high sugar, high saturated fat, and ultra-processed foods will help you keep a healthy gut microbiota. A balanced plant-based diet can help fend off harmful bacteria, avoid inflammation and contribute to optimal gut function. 

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