short-chain-fatty-acids-and-the-intestinal-barrier

Short-Chain Fatty Acids and the Intestinal Barrier

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By now you are likely familiar with the concept of the microbiome and its broad action in the role of a healthy gut barrier, immune system function, and wellness at large. You may not be as familiar with the concept of short-chain fatty acids and their symbiotic interplay — connecting our diet, our gut bugs, and our intestinal barrier.

Short-chain fatty acids (SCFAs) are common bacterial metabolites. That is, they are produced by bacteria inside the intestinal lumen when these bacteria ferment indigestible carbohydrates or dietary fiber. Your bacteria eat what you eat.

Thus, a diet rich in dietary fiber will feed your gut bacteria; and the gut bacteria produce SCFAs as a by-product. Most abundant are butyrate, acetate, and propionate which make up 90-95% of SCFAs in the colon.

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image from: Hoeppli RE, Wu D, Cook L and Levings MK (2015) The environment of regulatory T cell biology: cytokines, metabolites, and the microbiome. Front. Immunol. 6:61. doi: 10.3389/fimmu.2015.00061

SCFAs play several important roles inside the gut lumen

Foremost, SCFAs are a preferred fuel source for the cells lining the large intestine/colon, promoting the growth of new cells and can repair those cells which have been damaged. They have a profound anti-inflammatory effect by inducing and selectively expanding T-regulatory cells (Tregs) in the large intestine.

Tregs reduce Th17 activity which is pro-inflammatory. SCFA’s have also been shown to improve (heal and seal) the intestinal barrier by stimulating mucus production. Recent research also suggests SCFAs can improve whole body glucose tolerance and insulin sensitivity, and promote satiety.

So, how can we increase the amount of short-chain fatty acids in our digestive tract?

In a perfect scenario, our innate requirements for SCFAs are met through dietary consumption of resistant starches and fibers (undigestible carbohydrates) which upregulate the commensal bacteria in our microbiome that produce these SCFAS. The best fiber sources are as follows:

  • Inulin: artichokes, garlic, leeks, onions, wheat, rye, asparagus
  • Fructooligosaccharides (FOS): bananas, onions, garlic, asparagus
  • Resistant starch: grains (barley, rye), beans, green/under-ripe bananas, legumes, potatoes
  • Pectin: apples, apricots, carrots, oranges, plums, pears, peaches
  • Guar gum

Butyrate is also naturally occurring in high fat dairy such as grass-fed butter or ghee (clarified butter) and raw milk. Butter is about 3-4% butyrate so about 10g (2 TBSP) of butter daily would equal about 300 mg of butyrate.

Low levels of SCFAs found in even ‘healthy’ or ‘gut-healing’ diets

Unfortunately, the average American intake of fiber falls far below ideal recommended and diversified levels. Furthermore, many people on the paths to improving gut health may find themselves on a fiber-restricted diet for a variety of reasons including SIBO or colitis.

Many people avoid dairy or gluten containing grains, as these proteins can have adverse effects on the gut barrier by releasing the zonulin barrier protein. Thus, supplementation (mostly in the form of butyrate salts) is often recommended on intestinal healing programs.

Most clinical trials, to date, have established a butyrate dose of 300 mg to be safe and effective at improving digestive function and healing leaky gut symptoms. It can often take several weeks of using a butyrate supplement to experience symptom improvement.

Wondering if your gut may be lacking these essential short-chain fatty acids?

Test don’t guess! New Vibrant Gut Zoomer 3.0 will measure and report 4 short chain fatty acid metabolites:

  • acetic acid/acetate
  • butyric acid/butyrate
  • propionic acid/propionate
  • valeric acid/valerate

Additionally, the test reports relative abundance of bacteria which PRODUCE these SCFA’s, particularly butyrate, to determine if there is dysbiosis which would impair endogenous SCFA synthesis in the gut.

It is not only important to measure SCFA levels, but also to measure levels of the microbes responsible for producing SCFAs to determine a true root cause if deficiency exists.

References:
https://science.sciencemag.org/content/341/6145/463
https://www.ncbi.nlm.nih.gov/pubmed/23908210
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3070119/
https://www.ncbi.nlm.nih.gov/pubmed/30717248

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