Gut instincts

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If preventing diabetes, heart disease and weight gain haven’t convinced you enough to bump up your fiber intake, chew on this fact. A higher fiber diet protects one of the most important systems in your body, your immune system. With over 210,000 deaths due to COVID, it’s important to keep the inhabitants of your gut happy, and healthy.

Your gut (notably the cecum of the large intestine) is home to millions of powerful bacteria that are working continually to prevent and protect us from disease. Over 60% of our immunity is housed in the lining of our guts. Remember the old adage, “garbage in, garbage out”? This certainly applies to our gut microbiome.

Gut check

Quite simply, our gut microbiome is the collection of genetic microorganisms (read DNA) that live in the body’s gastrointestinal tract and control several physiologic functions.

It’s made up of bacteria, viruses, and fungi- some good, some not so good. This collection aids in the regulation of immunity, digestion, metabolism, and risk for disease. Our gut microbiome is influenced by several things including whether or not we were breastfed, antibiotic and other drug use, hormonal changes, stress, sleep, and food and beverage intake.1 Changes in lifestyle and diet can impact the gut microbiome dramatically.

Wild, wild west

In addition to being bad for a heart, a Western-style diet has been found to be not so great for the human gut, in more ways than one.

Research has shown that a low-fiber diet, high in sugar and fat, may be the reason for the decline in certain beneficial gut bacteria. The consequences of these changes may add to the increased development of certain chronic inflammatory diseases including intestinal bowel disease (IBD), colorectal cancer, allergies, autoimmune diseases, and obesity.

Scientists believe a Western diet impacts our guts in a negative way as they may be low in fermentable fibers that aid in the digestion of nutrients. A previous study from Cell magazine showed that when the colon is ‘deprived’ of dietary fiber, it may lead to the destruction of the protective mucous barrier in the colon. This can cause colitis due to a pathogen called Citrobacter rodentium. 3

In addition, a systematic review and meta-analysis of over 60 studies including nearly 3,000 subjects compared high fiber to low fiber diets. The researchers note that different types of fiber may impact the type and number of bacteria produced such as short-chain fatty acids (SCFA). Short-chain fatty acids are important as they regulate the release of chemicals in the body that reduce inflammation. 4

Results of the study showed that two types of fiber (fructans and galacto-oligosaccharides) greatly improved the number of Bifidobacterium spp. and Lactobacillus spp- two types of probiotics that have been found to aid in gut motility, the reduction of infectious disease, production of vitamins, and reduction in symptoms of IBS. 4 These bacteria may also impact the prognosis of critically ill patients as suggested in a recent study investigating levels of short-chain fatty acids in a critically ill population. 5

Fructans and Galacto-oligosaccharides in food

Let us put the scientific terms into food. Fructans are found in wheat, onions, garlic, and inulin, a type of fiber found in barley, asparagus, and jicama. Fructan intake can be increased by:

  • Switch from white bread and pasta to 100% whole wheat bread and pasta.
  • Using farro, bulgur, or wheat berries in grain salads.
  • Season soups and sauces with garlic.
  • Adding onions to sandwiches, wraps, soups, and salads.
  • Try asparagus spears and jicama sticks with hummus or another dip.

Galacto-oligosaccharides are found naturally in dairy products as well as plant-based foods including beans, lentils, and soybeans. Below are tips to improve your intake:

  • Swap Greek yogurt for sour cream in your favorite dip.
  • Use beans in place of beef in tacos or other dishes.
  • Enjoy lentil soup with onions and garlic.
  • Add beans to soup, salad, and grain bowls.
  • Try edamame as a snack in place of chips or pretzels.

Don’t forget about other fiber found in other fruits and vegetables! The more diverse your fiber intake, the more diverse your gut bacteria. There are plenty of delicious ways to take care of your gut.

Lisa Andrews, MEd, RD, LD


  2. Sonnenburg E.D., Smits S.A., Tikhonov M., Higginbottom S.K., Wingreen N.S., Sonnenburg J.L. Diet-induced extinctions in the gut microbiota compound over generations. 2016; 529: 212-215
  3. Desai MS, Seekatz AM, Koropatkin NM, Kamada N, Hickey CA, Wolter M, Pudlo NA, Kitamoto S, Terrapon N, Muller A, Young VB, Henrissat B, Wilmes P, Stappenbeck TS, Núñez G, Martens EC. A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility. Cell. 2016 Nov 17;167(5):1339-1353.e21
  4. So D, Whelan K, Rossi M, Morrison M, Holtmann G, Kelly JT, Shanahan ER, Staudacher HM, Campbell KL. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. Am J Clin Nutr. 2018 Jun 1;107(6):965-983.
  5. Nakahori Y, Shimizu K, Ogura H, Asahara T, Osuka A, Yamano S, Tasaki O, Kuwagata Y, Shimazu T. Impact of fecal short-chain fatty acids on prognosis in critically ill patients. Acute Med Surg. 2020 Aug 25;7(1):e558.

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