Eat more fiber’ is a common medical recommendation, but what does fiber actually do?
If you’re like many Americans, you’ve probably been admonished by your doctor to eat more fiber. And you’ve likely also seen countless brands touting their product as a “great source for fiber” when you visit the cereal aisle of the grocery store. Such admonitions and marketing is great, in this case, because the American Society for Nutrition says that only 7% of U.S. adults are getting enough fiber − meaning the majority of us are at greater risk of chronic conditions including heart disease and diabetes.
While adults and kids need at least 25 to 35 grams of fiber daily, most Americans only get about 15 grams a day. One of the reasons experts say many aren’t getting enough fiber is because a lot of people don’t understand what fiber is, why it’s important and what the nutrient actually does for the body.
What is fiber?
Dietary fiber, also called roughage or bulk, is a carbohydrate that helps the body with digestion and the regulation of how sugar is processed and used. While most carbs are broken down into glucose and then converted to energy, fiber cannot be broken down and instead passes through the body relatively intact.
Another thing that makes the nutrient unique is that there are different forms of fiber in a variety of foods. “Dietary fiber is not just one thing, it’s a family of different types of carbohydrates… and no single kind of fiber does it all,” says Karen Collins, MS, a registered dietitian and nutrition advisor to the American Institute for Cancer Research. The main two varieties of fiber include soluble fiber that dissolves in water, and insoluble fiber that cannot. Each are important for health and wellbeing.
What does fiber do for the body?
Fiber has multiple functions and soluble fiber and insoluble fiber each have their own purposes. Soluble fiber helps lower one’s cholesterol and one’s glucose levels. Insoluble fiber helps move food through one’s digestive system, promoting regular bowel movements.
But dietary fiber’s health benefits go beyond that. “Most people think of fiber as a way to prevent constipation, but it does so much more,” explains Josh Redd, NMD, the founder of RedRiver Health and Wellness and author of “The Truth About Low Thyroid.” “It also helps control blood sugar levels, supports heart health and aids in weight management.” He explains that another of fiber’s most critical roles is that it helps “dampen inflammation by improving gut microbiome health.” Inflammation has been tied to a host of physical and mental health conditions including tissue damage, anxiety, and depression.
What’s more, prebiotics − a form of soluble fiber − “serve as food for the good bacteria in the gut,” Redd says. Such bacteria produces “short-chain fatty acids which nourish cells that line the colon and regulate immunity.”
Collins says that fiber is essential in keeping one’s body running as it should, in part, because the foods that supply dietary fiber also supply “lots of other nutrients and plant compounds that all work together to support health and reduce risk of our most common chronic diseases.”
She says such a combination of nutrients have many advantages including lowering one’s risk of cardiovascular disease by “helping to keep cholesterol and blood pressure in a healthy range,” plus lowering one’s risk of type 2 diabetes (“studies consistently tie diets higher in fiber with lower risk of diabetes,” she says), and also reducing one’s risk of cancer. “The American Institute for Cancer Research grades evidence strong that dietary fiber reduces risk of colorectal cancer, which for both men and women in the U.S. is the third most common cancer,” Collins explains.
Can fiber help you lose weight?
Beyond such benefits, fiber has also been tied to weight management by regulating the body’s use of sugars and by keeping hunger pangs down. “Some studies suggest that higher dietary fiber may also influence gut hormones that affect appetite regulation,” says Collins. “Foods high in fiber also tend to be less concentrated in calories, so you can eat filling portions with fewer calories,” she adds.
Alice Lichtenstein, DSc, director of the Cardiovascular Nutrition Team at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, explains that fiber-rich foods also help with healthy weight management, “due to the satiety factor” of the carbohydrate helping one feel full after a meal. She says the nutrient slows the rate of digestion and the rate of glucose absorption, and that “dietary patterns relying on a variety of fiber-rich foods are less likely to contain quickly digested and calorie-dense foods.”
Perhaps the best news of all, Collins says, is that reaping the benefits of including fiber in one’s diet doesn’t have to be an “all or nothing” approach. “Each increase in daily fiber consumption helps,” she says.