The term postbiotic refers to the products that microbes in the gut produce. As mentioned in Trust your Gut, these can refer to vitamins, enzymes or short chain fatty acids. Short-chain fatty acids (SCFAs) are an important component of a healthy digestive system and research suggests SCFAs may positively impact other processes throughout the body as well.
SCFAs are naturally produced in the colon from fermentable fiber and resistant starches that are eaten but not digested in the small intestine. See the list in box 2 for examples. There are three main types of SCFAs: propionic, acetic, and butyric acid. Butyric acid (also known as butyrate) is the preferred energy source for epithelial colonocytes, which line the colon walls and act as the body’s barricade from intestinal pathogens - or the bad bacteria.4 A diverse and healthy microbiome is rich in SCFAs to strengthen the gut lining and promote mucus production for added protection. Luckily, SCFAs are naturally made; we just need to feed our system with plenty of fiber.
SCFAs in abundance are associated with a healthy gut microbiome. They assist in managing symptoms related to irritable bowel syndrome (IBS) as well as the effects of intestinal bowel diseases (IBDs) like Crohn’s and ulcerative colitis.1
Fermentable fiber is also referred to as soluble fiber, which is used by gut bacteria for energy. Fermentation occurs in the process of fiber being broken down, creating energy that supports gut health and other biological processes. Gas is a common byproduct of the fermentation process. Fermentable foods include sweet potato, carrots, and apples and many other fruits and vegetables, plus oats and quinoa.
Resistant starches are also a type of fiber found in plants that the body does not fully digest. They are only used for fuel by certain bacteria. As a result, fermentation is inhibited and and these fiber sources act more similarly to insoluble fiber. Health benefits of resistant starches include increased fullness (satiety) and reducing blood sugar levels. Resistant starches are a good source of SCFA. Sources of resistant starches include baked potatoes, cooked (and cooled) rice and legumes. Resistant starches are formed due to changes in chemical properties during the heating and cooling periods.
Increasing your SCFAs
Eating a high fiber diet including plenty of soluble (or fermentable) fiber is key to building a strong microbiome and SCFA production. Additionally, sources of resistant starches are also helpful. These most often come from potatoes being cooked and cooled before eating. (They can be reheated or cooked again after the cooling process.) Probiotics such as yogurt, sauerkraut, kimchi, soy products like tamari and tempeh, as well as aged cheeses and sour cream also play an important role in SCFA production.5
Beyond the gut
Current studies explore the role of SCFAs in the brain and other organs throughout the body. They may play a critical role in the gut-brain connection and potentially influence hormones contributing to psychiatric and neurologic disorders.4,6
High-fiber diets are associated with active enzyme production that can improve heart health, obesity, type 2 diabetes, and cholesterol levels.3,4,7,8 SCFAs are potential supporters of the immune system and may decrease inflammation in connection with atherosclerosis.9,10 While all of these potential benefits are being explored, definitive research is lacking and more research is needed.
A diet rich in probiotics and high-fiber foods, particularly soluble fiber, is key to maintaining a steady supply of these important fatty acids and overall good gut health. For more information on types of fiber, see Getting Familiar with Fiber.
As interest in the relationship between our bodies and the gut microbiome increases, studies are exploring direct and indirect impacts of SCFAs on the following:
Gut health: antimicrobial properties, Irritable Bowel Syndrome (IBS), Intestinal Bowel Disease (IBD), loral microbiome, gut homeostasis, and cancer
Brain health: hormones/endocrine system, psychiatric and neurologic disorders
Cardiovascular health: enzyme production
Obesity: lipid metabolism
Type II diabetes: blood glucose regulation and insulin sensitivity
Cholesterol: immune system and anti-inflammation.
References:
Shin Y, Han S, Kwon J, et al. Roles of Short-Chain Fatty Acids in Inflammatory Bowel Disease. Nutrients. 2023;15(20):4466. Published 2023 Oct 21. doi:10.3390/nu15204466
Singh V, Lee G, Son H, et al. Butyrate producers, "The Sentinel of Gut": Their intestinal significance with and beyond butyrate, and prospective use as microbial therapeutics. Front Microbiol. 2023;13:1103836. Published 2023 Jan 12. doi:10.3389/fmicb.2022.1103836
Martin-Gallausiaux C, Marinelli L, Blottière HM, Larraufie P, Lapaque N. SCFA: mechanisms and functional importance in the gut. Proc Nutr Soc. 2021;80(1):37-49. doi:10.1017/S0029665120006916
Liu H, Wang J, He T, et al. Butyrate: A Double-Edged Sword for Health?. Adv Nutr. 2018;9(1):21-29. doi:10.1093/advances/nmx009
Markowiak-Kopeć P, Śliżewska K. The Effect of Probiotics on the Production of Short-Chain Fatty Acids by Human Intestinal Microbiome. Nutrients. 2020;12(4):1107. Published 2020 Apr 16. doi:10.3390/nu12041107
Malec A. Butyrate Supplements for Gut Health: Does butyric acid really work and is it safe? Consumer Labs. https://www-consumerlab-com.bastyr.idm.oclc.org/answers/butyrate-supplements-for-gut-health/butyrate-supplements/?search=butyrate Published March 28, 2022; updated April 17, 2023. Accessed February 19, 2024.
He J, Zhang P, Shen L, et al. Short-Chain Fatty Acids and Their Association with Signalling Pathways in Inflammation, Glucose and Lipid Metabolism. Int J Mol Sci. 2020;21(17):6356. Published 2020 Sep 2. doi:10.3390/ijms21176356
Pham NHT, Joglekar MV, Wong WKM, Nassif NT, Simpson AM, Hardikar AA. Short-chain fatty acids and insulin sensitivity: a systematic review and meta-analysis. Nutr Rev. 2024;82(2):193-209. doi:10.1093/nutrit/nuad042
McRorie JW. Fiber. Linus Pauling Institute: Micronutrient Information Center. https://lpi.oregonstate.edu/mic/other-nutrients/fiber. Published 2004; updated March 2019; reviewed June 2019. Accessed February 19, 2024.
Feng Y, Xu D. Short-chain fatty acids are potential goalkeepers of atherosclerosis. Front Pharmacol. 2023;14:1271001. Published 2023 Nov 13. doi:10.3389/fphar.2023.1271001
Comentários