The Amazing, Little-Known Benefits of Dietary Fiber

You know fiber’s good for you. Millions of people boost their fiber intake with fruits and vegetables – or take fiber supplements like Metamucil -- to help with healthy digestion and elimination. A few well-informed people know fiber can also help lower your cholesterol levels. But the latest medical research reveals that the benefits of fiber go way beyond what we’ve been told. In fact, fiber has some super health benefits you never imagined.

Fiber Regulates Your Immune System

Research in Australia demonstrates that fiber triggers an important part of the immune system that fights off viruses -- including the flu. The study at Monash University found fiber feeds probiotic bacteria in your digestive tract, increasing the production of short-chain fatty acids. These fatty acids play two important roles in your overall immune health -- keeping harmful excessive inflammation in the lungs from getting out of control, and activating T cells that can efficiently zap an invading flu virus.¹ "We typically find that a certain treatment turns our immune system either on or off," says researcher Benjamin Marsland. "What surprised us was that dietary fiber was selectively turning off part of our immune system (the harmful inflammatory part), while turning on another, completely unrelated (virus killing) part of our immune system." And there’s more...

Fiber Fights Food-Borne Pathogens

At the same time, research in Japan shows that fiber can protect against food poisoning, especially from Salmonella bacteria – a common culprit in food-borne illness. The study shows another positive interaction between those short-chain fatty acids in your digestive tract and your immune system. The fatty acids link up to proteins that are part of what is called the inflammasome complex – a protein structure that alerts the immune system to a Salmonella invasion and other pathogens. And the alert leads immune cells to quickly destroy illness-causing microbes.²

Fiber Helps Heart Health

Research has also established solid evidence that dietary fiber is crucial for better heart health. For example, a Norwegian study indicates that for people suffering heart failure, extra fiber is associated with reduced risk of death and can even eliminate the need for a heart transplant. According to these findings, consuming extra fiber encourages the growth of a more diverse and healthier collection of probiotic bacteria in the digestive tract that keep the heart functioning at a higher level. And these researchers think that if you have a faltering heart, are eating too much meat – more than about two or three times a week – and too little fiber, this may increase your need for a heart transplant.³ "Our findings suggest that the altered microbiota (probiotic bacteria) composition (in the digestive tract) found in patients with chronic heart failure might be connected to low fiber intake," warns researcher Cristiane Mayerhofer. Added to that analysis, a review study in New Zealand shows that when you eat large amounts of high fiber foods you can drop your risk of coronary heart disease and stroke, as well as type 2 diabetes, by 16 to 24 percent. This review looked at the results of 185 studies and 58 clinical trials.⁴ The researchers concluded that "The benefits of fiber are supported by over 100 years of research into its chemistry, physical properties, physiology, and metabolic effects." This isn’t surprising. Fiber helps control blood sugar levels. In people with diabetes, fiber — particularly soluble fiber — can slow the absorption of sugar. Also, a healthy diet that includes insoluble fiber may reduce the risk of developing type 2 diabetes to begin with.

Fiber Helps You Lose Weight, Fight Colon Cancer

High-fiber foods are a critical part of any healthy weight loss regimen. For one thing, they’re more filling than low-fiber foods, so you’re less likely to overeat. What’s more, you won’t become hungry again as quickly. High-fiber foods also contain fewer calories, by volume, when compared to other foods. “High fiber foods may help reduce your overall calorie intake and help you maintain a healthy weight, which is vital to reducing cancer risk,” says Erma Levy, research dietitian in Behavioral Science at MD Anderson Cancer Center.⁵ One of the first to make the connection between a high-fiber diet and low rates of cancer was Dr. Denis Burkitt, an Irish surgeon. In the 1950s Dr. Burkitt traveled to Africa on a missionary trip to help improve the health of the people living there. While he found numerous health problems, what he didn’t find was colorectal cancer. While Americans and other Western populations had a lot of colon problems, including high rates of cancer, the Africans he studied had an astonishingly low rate of colon problems and cancers. Dr. Burkitt realized that Africans ate large amounts of beans, corn, and other high-fiber foods in their original state. Americans, by contrast, were mainly eating processed foods.⁶ Mary Daly, M.D., chair of the department of clinical genetics at Fox Chase Cancer Center in Philadelphia, says because fiber passes quickly through the colon, it perhaps “flushes out cancer-causing compounds.” It may even “change these compounds, making them less harmful.” That being said, Dr. Daly and her counterparts agree that there hasn’t been absolute scientific evidence that fiber prevents colon cancer. However, in that large research review out of New Zealand I mentioned earlier, a high-fiber diet lowered risk of colorectal cancer by 16 to 24 percent. In addition, studies suggest that increasing your dietary fiber intake — especially cereal fiber (such as bran, brown rice, whole grains) — is associated with a reduced risk of dying from all cancers.

Increasing Fiber in Your Diet

Fiber is commonly classified as soluble, meaning it dissolves in water, or insoluble, meaning it doesn't. Soluble fiber is found in oats, peas, beans, apples, citrus fruits, carrots, barley and psyllium. Insoluble fiber is found in whole wheat flour, wheat bran, nuts, beans and vegetables such as cauliflower, green beans and potatoes. To reap the greatest health benefit, eat a wide variety of high-fiber foods, including plenty of fruits and vegetables, according to the Mayo Clinic.⁷

Here are some easy ways for an instant fiber boost:

Go nuts: Nuts are great for dessert, snacks or even sprinkled on salads. A cup of nuts usually has about nine grams of fiber as well as other nutrients that are beneficial for heart health.

Don't eat chips: When you snack on chips or crackers you're usually missing out on fiber. Munch on an apple (four or more grams of fiber), blueberries (almost four grams in a cup) or other fruits instead.

Fill your plate with veggies: All of your meals should include a cornucopia of vegetables. High fiber veggies include: sweet potato (four grams in a cup); asparagus (one gram in every three spears) and squash (nine grams per cup). But there are plenty more to choose from!

Trompette A, Gollwitzer ES, Pattaroni C, Lopez-Mejia IC, Riva E, Pernot J, Ubags N, Fajas L, Nicod LP, Marsland BJ. Dietary Fiber Confers Protection against Flu by Shaping Ly6c- Patrolling Monocyte Hematopoiesis and CD8+ T Cell Metabolism. Immunity. 2018 May 15;48(5):992-1005.e8. doi: 10.1016/j.immuni.2018.04.022. PMID: 29768180. https://pubmed.ncbi.nlm.nih.gov/29768180/
Tsugawa H, Kabe Y, Kanai A, Sugiura Y, Hida S, Taniguchi S, Takahashi T, Matsui H, Yasukawa Z, Itou H, Takubo K, Suzuki H, Honda K, Handa H, Suematsu M. Short-chain fatty acids bind to apoptosis-associated speck-like protein to activate inflammasome complex to prevent Salmonella infection. PLoS Biol. 2020 Sep 29;18(9):e3000813. doi: 10.1371/journal.pbio.3000813. PMID: 32991574; PMCID: PMC7524008. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000813
Mayerhofer CCK, Kummen M, Holm K, Broch K, Awoyemi A, Vestad B, Storm-Larsen C, Seljeflot I, Ueland T, Bohov P, Berge RK, Svardal A, Gullestad L, Yndestad A, Aukrust P, Hov JR, Trøseid M. Low fibre intake is associated with gut microbiota alterations in chronic heart failure. ESC Heart Fail. 2020 Apr;7(2):456-466. doi: 10.1002/ehf2.12596. Epub 2020 Jan 24. PMID: 31978943; PMCID: PMC7160496. https://onlinelibrary.wiley.com/doi/full/10.1002/ehf2.12596
Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet. 2019 Feb 2;393(10170):434-445. doi: 10.1016/S0140-6736(18)31809-9. Epub 2019 Jan 10. Erratum in: Lancet. 2019 Feb 2;393(10170):406. PMID: 30638909. https://pubmed.ncbi.nlm.nih.gov/30638909/
MD Anderson. How Fiber Helps Lower Your Cancer Risk. https://www.mdanderson.org/publications/focused-on-health/how-fiber-helps-lower-your-cancer-risk.h11-1590624.html
https://www.webmd.com/diet/features/fiber-cancer#2
Mayo Clinic. Healthy Eating. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983