What are Short Chain Fatty Acids?

What are Short Chain Fatty Acids?

One of the most important functions our gut microbiome performs is to produce anti-inflammatory substances called Short Chain Fatty Acids (SCFAs). Here’s what you need to know about them.

 

What are SCFAs?

Our gut is home to a complex and diverse population of beneficial bacteria. We keep our gut bacteria healthy by consuming fibre as part of an everyday diet. Dietary fibres (think vegetables, fruits, nuts, and wholegrains) are specific types of carbohydrates that cannot be broken down by the human body. Instead, fibre passes through to our large intestine (colon) where our gut bacteria are able to feed upon and ferment them. As a by-product of microbial fermentation, our gut bacteria produce very small anti-inflammatory substances called SCFAs. The three main types of SCFAs are called butyrate, propionate, and acetate. SCFAs play an important role in digestive function, immunity, metabolism, and mental health. Here’s exactly what they do.

 

1. Promote a healthy gut lining

Butyrate is the main fuel source for colonocytes (the cells that line the gut). When the cells are healthy, they are able to fulfil their functions properly, including maintaining the strength and integrity of the gut lining (epithelium). A healthy gut lining increases your ability to absorb vitamins and minerals, prevents potentially harmful toxins and pathogens from entering the bloodstream, and reduces the long-term risk of colon cancer.

 

2. Reduce inflammation

One of the most important benefits that SCFAs may provide to human health is to regulate chronic levels of inflammation. The gut comprises 70-80% of the body’s immune cells, and is both directly and indirectly in communication with the gut bacteria. Maintaining immune function in the gut is a unique challenge, requiring a balance between eliminating foreign pathogens when appropriate, while maintaining self-tolerance to avoid autoimmunity. Inflammation is the natural defence response of the immune system to a foreign attacker. However, prolonged inflammation of the gut can lead to a number of health concerns.

The overall anti-inflammatory effects of butyrate and propionate is achieved through several mechanisms, with the joint goal of inhibiting the expression and production of pro-inflammatory cytokines. Individuals with Inflammatory Bowel Disease often have lower levels of butyrate, and fewer butyrate-producing bacteria residing in their guts. In fact, acute administration of butyrate to patients suffering from Ulcerative Colitis show clinically significant reductions in endoscopic scores of inflammation. 

 

3. Promote mental wellbeing

SCFA production has been linked to improved mental well-being, including how we experience anxiety, stress, and depression, as well our rate of cognitive decline as we age. Importantly, the connection between the gut and the brain is a two-way street. So when we are feeling anxious or stressed, this often leads to gut-related symptoms too, including abdominal pain, diarrhoea, bloating, and constipation. SCFAs interact with the brain via several complex and overlapping pathways. Within the gut, SCFAs are thought to communicate with the brain via the vagus nerve (a long neuronal projection that connects peripheral organs to the central nervous system). Since SCFAs can enter the bloodstream, they have also been shown, in some cases, to cross the blood-brain barrier. Once in the brain, SCFAs might play a role as a gene expression regulator and immune modulator. Other studies have shown that butyrate can support and maintain the integrity of the blood-brain barrier.

 

4. Regulate blood sugar levels

SCFAs have shown benefits for human metabolism and energy. The increased production of butyrate has been linked to improved glucose control via the production of glucose locally in the gut (a process called gluconeogenesis). Regular consumption of fermentable fibre may be important to improve insulin sensitivity and manage blood sugar levels in individuals with Type 2 diabetes.

 

5. Reduce risk of colon cancer

The SCFA butyrate promotes the health and integrity of the gut lining which reduces your overall risk of developing colon cancer. Butyrate has also been shown to inhibit the growth and differentiation of a variety of human colon cancer cells.

 

Take-home message

SCFAs are important substances that are produced by our gut microbiome. They can:

  • Promote a healthy gut lining
  • Enhance nutrient absorption
  • Prevent harmful pathogens
  • Reduce inflammation
  • Promote mental wellbeing
  • Improve insulin sensitivity
  • Reduce risk of colon cancer

The most effective way to increase SCFA production is by consuming a diversity of fermentable fibres, like oats, onion, garlic, artichokes, banana, chicory root, and leeks. If you struggle to get enough fibre in your diet, consider taking a prebiotic fibre supplement.