Short-Chain Fatty Acids Regulate Immunity, Protect the Brain, and Fight

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Produced by the fermentation of dietary fiber in the intestines, short-chain fatty acids are crucial in maintaining a healthy weight, immune system, and mind.

Short-chain fatty acids are vital for intestinal immune system regulation and brain health. However, they are not produced by the breakdown of fat but through the fermentation of dietary fiber by intestinal bacteria. Meals rich in dietary fiber, combined with proper exercise, can help you maintain normal levels of short-chain fatty acids.

Short-Chain Fatty Acids

Short-chain acids are produced when dietary fiber, undigested in the small intestine, enters the large intestine and is fermented by intestinal microorganisms.

The main components of short-chain fatty acids are acetate, propionic acid, and butyric acid.

1. Acetate

Acetate accounts for around 60 percent of short-chain fatty acids. It is absorbed into the bloodstream by the intestines and can reach the brain via the blood-brain barrier as blood circulates, so it has a significant effect on the nervous system.

Acetate is involved in synthesizing fat and cholesterol in the liver and muscles. It supports the heart and brain when the body is low on energy, regulates appetite, promotes energy, and reduces hunger by affecting the hypothalamus. It is particularly crucial for people who want to control their weight.

2. Propionic Acid

About 20 percent of short-chain fatty acids are propionic acids. After being absorbed into the bloodstream by the intestines, propionic acid reaches its first stop, the liver, where it participates in glucose metabolism.

Propionic acid stabilizes blood sugar levels and reduces cholesterol synthesis, reducing total cholesterol levels and low-density lipoprotein (LDL, or “bad”) cholesterol in the blood, reducing the risk of cardiovascular disease. This is confirmed by a study published in the European Heart Journal.

A 2019 study on mice with induced hypertensive cardiovascular injury published in Circulation found that propionic acid significantly reduced cardiac hypertrophy, fibrosis, vascular dysfunction, and hypertension. The study highlighted the immunomodulatory effects of short-chain fatty acids and their importance for cardiovascular health.

However, propionic acid is a double-edged sword, and too much of it can harm the brain. Research has found that excessive propionate levels may lead to Alzheimer’s disease through a variety of mechanisms.

3. Butyric Acid

Butyric acid accounts for around 15 percent of short-chain fatty acids. Its primary function is to protect the integrity of the intestinal mucosa. The intestinal mucosa forms a protective barrier of the intestine, shielding harmful substances from the outside and allowing only nutrients in, which is crucial to overall health.

The most crucial function of butyric acid is to protect our blood-brain barrier. This is a barrier separating the brain and blood flow. If harmful substances such as bacteria and viruses enter the brain, they can do a lot of damage. Butyric acid protects the brain from chronic inflammation, a hidden culprit of many neurological diseases.

Butyric acid reduces systemic inflammation, including intestinal inflammation. It also inhibits pro-inflammatory cytokines, reducing inflammatory responses in the intestines and the whole body.

A comprehensive 2021 study showed that butyrate mediates the effects of intestinal microbiota on the immune system and plays a key role in maintaining intestinal immune balance, suppressing excessive inflammation and limiting the growth of pathogenic bacteria.

To maintain good health, the immune system must be balanced—neither weak nor overly strong. In the immune system, cytokines that suppress inflammation and promote inflammation exist in tandem, playing a mutually dependent and balancing role.

In fact, the essence of human health is “balance,” whether it is the balance of energy levels or biochemical levels, they are all key to good health.

Comprehensive Effects of Short-Chain Fatty Acids

The following are the main effects of short-chain fatty acids:

Maintain Intestinal Health: These acids are essential for maintaining the integrity of the intestinal mucosa and enhancing intestinal barrier function. The intestinal barrier is critical for maintaining intestinal homeostasis and preventing harmful microorganisms and metabolites from entering the bloodstream.
Reduce Inflammation: Short-chain fatty acids can inhibit a variety of inflammatory cytokines and have a certain protective effect for inflammatory bowel diseases, such as Crohn’s disease and colon ulcers. Some studies have suggested that short-chain fatty acids may regulate innate immune recognition and cytokine production, thereby intervening in the progression of inflammatory bowel disease.
Balance Blood Sugar and Fat: A comprehensive analysis published in January showed that short-chain fatty acids can significantly reduce fasting blood sugar levels, total cholesterol, and triglyceride levels.

Growing evidence supports the role of short-chain fatty acids as key mediators that may help prevent, reverse, and delay disease progression.

Research supports supplementing endogenous or exogenous short-chain fatty acids to improve inflammation, body weight, blood sugar regulation, and lipid metabolism. It is also beneficial for patients with diseases such as fatty liver disease, cardiovascular disease, Alzheimer’s disease, and Type 2 diabetes.

How to Maintain Healthy Levels of Short-Chain Fatty Acids

A diet rich in dietary fiber is key to maintaining healthy levels of short-chain fatty acids. The following foods support short-chain fatty acid production:

Whole Grains: Whole grains like oats and brown rice are rich in soluble and insoluble fiber. Research shows that oats help change the composition of the intestinal microbiota and promote the synthesis of short-chain fatty acids.
Legumes: These include lentils, chickpeas, and beans. Research shows that chickpeas have the potential to modulate the composition of the gut microbiome to promote intestinal health in humans.
Starchy Foods: Foods such as green bananas, potatoes, and rice contain lots of resistant starch. Studies have found that resistant starch in green bananas increases the production of short-chain fatty acids and regulates lipid metabolism. Resistant starch produces relatively large amounts of butyrate after fermentation by intestinal microbiota.
Fruits and Vegetables: Studies have shown that obese rats fed onion and apple had increased probiotic presence and concentrations of short-chain fatty acids.
Fermented Foods: Foods such as yogurt, kimchi, and sauerkraut are rich in probiotics, which help to actively regulate the intestinal microbiota and contribute to the production of short-chain fatty acids.
Prebiotics and Probiotics: You can supplement probiotics directly with strains such as Lactobacillus and Bifidobacteria or take prebiotics that provide nutrients to probiotics, such as oligofructose and inulin.

Exercise

In addition to supplementing dietary fiber, probiotics, and prebiotics, exercise promotes intestinal flora diversity and supports short-chain fatty acid production.

A study published in Nutrients in August showed that aerobic exercise, such as running, swimming, and cycling, can enhance the diversity and abundance of intestinal probiotics, including Lactobacillus and Bifidobacteria, thereby increasing the production of short-chain fatty acids.

In short, we must have enough dietary fiber in our meals and foods that promote the growth of probiotics and get enough exercise. This will ensure we have enough short-chain fatty acids, which are so crucial in protecting our body, brain, and spirit.

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