5 reasons to eat more fiber

No question: Fiber is great for your health. Unfortunately, in the latest Dietary Guidelines for Americans, fiber was among the most underconsumed nutrients in the U.S., with most adults falling short of getting the recommended 22–34 g of fiber per day (the exact amount you need depends on your age and sex).

Fiber is a carbohydrate—one of three main classes that also includes starches and sugars. But unlike those two, fiber doesn’t provide glucose energy. Our bodies are unable to break down fiber for fuel, so we use it in other ways, explains Angel C. Planells, MS, a Seattle-based registered dietitian. Dietary fiber can be classified as either soluble or insoluble (foods can contain both types).

• Soluble fiber absorbs water in the digestive tract to form a gummy material. It’s found in starchy vegetables, pulses (e.g. beans, lentils), and cereal grains such as oats.
  
  

• Insoluble fiber doesn’t react with water; it provides bulk to stool and helps keep contents moving through the digestive tract. Insoluble fiber is found in whole grains, apples, nuts, beans, and nonstarchy vegetables.

1. Reduces risk of type 2 diabetes

Remember the fiber intake recommendations we mentioned at the start of this article? Large studies have shown that adults who consistently meet or exceed their daily targets are 20–30% less likely to develop type 2 diabetes over time. Researchers writing in The Journal of Nutrition in 2018 noted a number of possible reasons: insoluble fiber may improve insulin sensitivity, a major risk factor for type 2 diabetes. Fiber can also be helpful for people already living with the condition, Planells notes. “Soluble fiber slows the absorption of glucose from food,” he says. “This can be helpful in regulating blood sugar levels.”

2. Supports heart health

Health experts have long known about the link between high fiber intake and reduced incidences of heart disease. One likely reason is that a high-fiber diet can improve cholesterol. Soluble fiber in particular can play a key role in decreasing levels of LDL cholesterol—the “unhealthy” kind—by soaking up excess LDL cholesterol and removing it from the body, helping to keep your arteries clear, Planells explains. What’s more, high fiber intake may support blood-pressure improvements in both healthy adults and those living with hypertension.

3. May lower cancer risk

Some evidence suggests that fiber-rich diets may help protect against certain types of cancer. Research has found that women who consumed the highest amounts of fiber were 8% less likely to develop breast cancer than those who consumed the least.

Meanwhile, multiple studies have found that diets high in fiber are associated with a decreased likelihood of developing colon cancer. Fiber may promote cell turnover in that area of the large intestine, preventing cancer cells from proliferating, says Lauren Slayton, R.D., founder of Foodtrainers in New York City.

4. Aids digestive function

Fiber is most famous for supporting laxation, better known as pooping. In taking on water, soluble fiber helps form soft, bulky stools. Insoluble fiber adds further bulk and helps sweep waste material through the body’s plumbing.

The other digestive trick up fiber’s sleeve? They help feed the probiotics, aka the healthy bacteria, living in your gut. As probiotics consume the fiber, some of the bacteria produce short-chain fatty acids believed to play a role in immunity, inflammation control, and more. “Just as we perform better when fed and nourished, the same can be said for probiotics,” says Slayton.

5. Supports weight management

And finally, all signs point to fiber being helpful for long-term weight management. Research shows that the more fiber people eat, the less weight they gain and the less their waist circumference grows over time compared to people who consume less fiber.

That’s not to say people who eat more fiber will magically lose weight, Planells clarifies. The weight effect is likely tied to fiber’s influence on our appetite and broader eating patterns: By filling us up quicker and for longer, fiber may make us less likely to have seconds at mealtime, for example, or reach for a bedtime snack.