Experts now believe that fiber does not protect against colorectal cancer, but fiber might prevent other digestive woes -- diverticulosis, gastroesophageal reflux disease (GERD), gallstones, and hemorrhoids.
- Fiber and diverticulosis. One study divided more than 43,000 men into five groups based on their fiber consumption. Those who ate the most insoluble fiber were nearly half as likely to develop diverticular disease (diverticulosis and diverticulitis) as men who ate the least insoluble fiber.
How does insoluble fiber protect against diverticulosis? This fiber type keeps stools soft and thus easier to pass; straining to pass hard stools is a major cause of diverticulosis.
- Fiber and GERD. According to one study, a high-fiber diet may help protect against GERD, according to a 2005 study. Researchers assessed the dietary habits of 371 adults, some of whom had GERD symptoms at least weekly. Participants who ate a higher number of calories and servings of fat per day were more likely to have GERD. But people who ate a diet high in fiber were 20% less likely to have GERD, regardless of their weight. Researchers are unsure how fiber protects against GERD.
- Fiber and gallstones. Women who eat a high-fiber diet may be at lower risk for gallstones, an analysis of data from the Nurses’ Health Study found. When the women were separated into five groups, those who ate the most total fiber were 13% less likely to need gallbladder surgery than those who ate the least. For insoluble fiber, the reduction in risk was 17%. Gallbladder surgery is needed when gallstones cause pain. Gallstones form when there is too much cholesterol in bile. Fiber probably lowers that cholesterol and thus decreases the chance of gallstone formation.
- Fiber and hemorrhoids. One metaanalysis found that fiber also may help treat hemorrhoids. Researchers looked at the results of seven studies that included a total of 378 people with hemorrhoids who were randomized to a fiber or placebo group for six weeks to three months. Overall, people in the fiber group were 47% more likely to have their symptoms improve or go away than people in the placebo group. Like diverticulosis, hemorrhoids can be worsened by straining to pass hard stools; a high-fiber diet helps make stools softer and easier to pass.
The Bottom Line: Fiber has benefits for your digestive tract, and fiber is great for your overall health, too, reducing your risk of heart disease, diabetes, and obesity. So keep eating that fiber -- and if you’re like most Americans, you should be eating more than your usual amount. The average American consumes only 5–20 g a day, yet experts recommend 30 g a day for men over 50 years old and 21 g for women over the age of 50.
To get the most benefit, mix up the types of fiber in your diet. Soluble fiber from oats, peas, beans, apples, citrus fruits, carrots, barley, and psyllium is the type that helps lower your blood cholesterol and reduce your risk of diabetes. The other type, insoluble fiber (from whole-wheat flour, wheat bran, nuts, and most vegetables), is best for the digestive tract.
