Short-chain fatty acids (SCFAs) are a group of fatty acids that play an essential role in the maintenance of health and the development of disease. Some common SCFAs include acetate, propionate, and butyrate.  

Short-chain fatty acids have a wide range of beneficial effects on health throughout the body due to their anti-inflammatory properties and positive influence on gut health and metabolism. These fatty acids are mainly produced by bacteria in the gut. SCFAs provide the primary fuel source for the cells lining your intestinal tract and also serve as an energy source for the rest of the body.

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What are Short Chain Fatty Acids?

Short-chain fatty acids (SCFAs) are a group of small fatty acids that contain one to six carbons, including acetic acid, propionic acid, and butyric acid. They are produced when microbes in the gut ferment partially- and non-digestible carbohydrates like prebiotic fibers and resistant starches, especially from plant foods.

Humans do not have complete enzymes to break down dietary fiber, so when you eat fiber, it passes through the upper digestive tract largely undigested and is fermented in the large intestine by microorganisms.

Bacteria colonize your digestive tract (microbiome) and break down fiber and resistant starches to produce SCFAs. Small amounts of SCFAs can also be made by fermenting some amino acids. The amount of SCFAs produced depends on dietary, individual, environmental, and gut microbiota factors.

What Are The Functions of Short Chain Fatty Acids?

SCFAs play many vital roles in the body, influencing health and disease. The functions of short-chain fatty acids include:

• Nourishing cells that line the intestines
• Regulating pH in the gut
• Helping to keep the microbiome balanced
• Positively impacting energy balance and blood glucose levels
• Balancing inflammation
• Influencing the gut-brain axis and brain health
• Reducing the risk of type 2 diabetes and heart disease
• Regulating appetite and metabolism to reduce obesity
• Providing up to 10% of your daily calories
• Increasing the body's ability to absorb minerals like calcium, iron, and magnesium

Types of Short Chain Fatty Acids

Different types of intestinal microbes produce different types and amounts of SCFAs. Each type of SCFA has specific functions and impacts within the body.

Acetate

Acetic acid or acetate is a two-carbon SCFA that makes up the highest percentage of SCFAs produced by your gut bacteria. It is mainly produced by Bifidobacteria, Lactobacillus, Akkermansia muciniphila, Prevotella, and Ruminococcus species.

Acetate plays an essential role in keeping the gut microbiome healthy and balanced by regulating pH to protect against pathogens and nourishing bacteria that produce another SCFA, butyrate, which is a vital source of energy for the cells lining the intestines. Acetate also helps regulate appetite and fat storage by influencing the gut hormone levels of glucagon-like peptide-1(GLP-1) and peptide-YY that impact food intake.

Proprionate

Propionic acid or propionate is a three-carbon SCFA. It is mainly produced by Bacteroidetes, Firmicutes, and Lachnospiraceae species of bacteria.

Like acetate, propionate also stimulates the release of the hormones peptide YY and GLP-1, which tell you when you feel satisfied after eating food. Studies suggest that propionate also helps to regulate inflammation within the gut and throughout the body.

Butyrate

Butyric acid or butyrate is a four-carbon SCFA. It is mainly produced by Faecalibacterium prausnitzii, Eubacterium rectale, and Roseburia species of bacteria in the gut.

Butyrate is the primary energy source for cells that line the colon and helps to keep them healthy, balancing inflammation and preventing leaky gut. Butyrate has also been shown to promote brain health and is involved with communication in the gut-brain axis.

Evidence-Based Health Benefits of Short-Chain Fatty Acids

Once produced by gut bacteria, SCFAs provide the main source of energy for the cells lining your large intestine. They also help regulate the gut's local environment, influencing the pH to control the balance of healthy microbes that reside there, regulating inflammation, and strengthening the intestinal lining to prevent a leaky gut.

In these ways, SCFAs contribute to improved digestion and a better balance of beneficial gut bacteria. Studies show that SCFAs are protective against some digestive disorders. For example, butyrate has been shown to help regulate the excess inflammation at the root of inflammatory bowel diseases, including Crohn's and ulcerative colitis. Research also suggests that supplementing with butyrate improves symptoms like abdominal pain in those suffering from irritable bowel syndrome.

In addition to nourishing the gut, short-chain fatty acids are used for other functions throughout the body. SCFAs are essential in regulating metabolism, appetite, and blood sugar balance. Due to these impacts, they seem to improve symptoms of type 2 diabetes, such as helping to control blood sugar levels and improve insulin resistance due to their influence on enzyme activity in the liver and muscle tissue. The metabolic impacts of SCFAs also help to regulate appetite and reduce the risk of obesity. They have been shown to influence fat metabolism by increasing fat burning and decreasing fat storage.

SCFAs also impact the brain. A key way that SCFAs influence the brain and cognition is by regulating communication in the gut-brain axis.

How to Test for Short Chain Fatty Acids

Several functional medicine laboratory tests can help you evaluate the balance of your gut microbiome that can influence your levels of short-chain fatty acids.

Comprehensive Stool Test

The composition of the diet strongly influences the gut microbiome and how many short-chain fatty acids are produced. Diets rich in fibers and polyphenols modulate the gut microbiome in beneficial ways to help increase the production of short-chain fatty acids.  

A comprehensive stool test like the GI Effects reflects the overall health and balance of the digestive tract by measuring a variety of microbes and intestinal health markers, including looking at levels of the SCFAs with percentages of acetate, butyrate, and propionate. It can also help patients understand how well they are breaking down and digesting fats, proteins, and carbohydrates, which can guide an individualized approach to nutrition based on the patient's unique needs.

Another option for assessing gut health and measuring levels of SCFAs is the GI 360 test. The GI 360 uses PCR, MALDI-TOF, and microscopy to evaluate the balance of microbes in the gut and assess inflammation. It analyzes the short-chain fatty acids produced by the colonic bacteria with a breakdown of the subtypes of short-chain fatty acids and their relative percentages.  

How to Increase Short-Chain Fatty Acids in Diet

Consuming a wide variety of plant foods and sources of fermentable fiber helps to feed the good bacteria in your gut so that they can produce adequate amounts of SCFAs.

Dietary fibers, including arabinoxylans, inulin, pectin, and fructooligosaccharides, as well as polyphenols found in plant foods and vitamin D, influence the balance of microbes in your gut. A well-balanced, anti-inflammatory diet incorporating a variety of plant-based foods promotes a variety of beneficial bacteria and suppresses potentially detrimental species, which helps to optimize the production of SCFAs.

Plant foods rich in fiber, such as fruits, vegetables, and legumes, provide substrates for your gut bacteria to produce short-chain fatty acids. The amount and types of fiber in your diet impact the balance of bacteria in your gut which affects the levels and types of short-chain fatty acids that are produced.

Some types of cheese, like parmesan, butter, ghee, and cow's milk, also contain small amounts of butyrate.

The best types of fiber to support the production of short-chain fatty acids in the colon include:

• Arabinoxylans found in cereal grains like wheat bran
• Inulin fiber found in artichokes, garlic, leeks, onions, wheat, rye, and asparagus
• Fructooligosaccharides (FOS) in various fruits and vegetables, including bananas, onions, garlic, and asparagus
• Resistant starch from green bananas, plantains, legumes, and rice or potatoes that have been cooked and then cooled before consumption
• Pectin in apples, apricots, carrots, and oranges

Summary

The balance of bacteria in your gut microbiome has wide-reaching impacts on health. One reason for this impact is their production of short-chain fatty acids. These small fatty acids are produced by beneficial bacteria in the large intestine when they break down and ferment fiber and resistant starch.

The most common SCFAs are acetate, butyrate, and propionate, which play essential roles in balancing health. They provide many digestive benefits and serve as the primary fuel source of the cells that line the intestine to help keep them healthy and prevent leaky gut. SCFAs help regulate the pH of the digestive tract and maintain a balance of healthy microbes in the gut microbiome. These impacts help reduce the symptoms of digestive conditions like inflammatory bowel disease and irritable bowel syndrome.

SCFAs also balance inflammation throughout the body, supporting metabolism and regulating appetite, blood sugar, and fat processing. These impacts can help with maintaining a healthy weight and preventing type 2 diabetes.

A diet rich in various high-fiber plant-based foods supports a balanced microbiome that can produce adequate amounts of SCFAs. High-fiber foods include beans, legumes, green bananas, avocados, asparagus, apples, oats, and citrus fruits.