Dietitians Say This 1 Surprising Tip Can Maximize Your Fiber Intake

You’ve probably heard a lot about the benefits of fiber, and for good reason. Fiber can help keep you regular and make you feel full, making it an important component of a healthy diet.

Not all fiber is the same, though: different types help the body in different ways. Generally, diet advice tends to focus on the distinction between soluble and insoluble fiber, and how to get a mix of both. But experts say there’s another set of categories that can really help you maximize your fiber intake.

Below, experts discuss a way of approaching this macronutrient that you’re probably not considering.

Meet the experts: Purna Kashyap, M.B.B.S., a gastroenterologist at Mayo Clinic in Rochester, Minnesota; Jessica Cording, M.S., R.D., registered dietitian and author of The Little Book of Game-Changers; Keri Gans, M.S., R.D., registered dietitian and author of The Small Change Diet; Rudolph Bedford, M.D., gastroenterologist at Providence Saint John’s Health Center in Santa Monica, California; Heidi J. Silver, R.D., Ph.D., research professor of medicine at Vanderbilt University Medical Center.

Fermentable vs. nonfermentable fiber

Again, many people interested in increasing their fiber intake tend to focus on soluble and insoluble fiber. According to the U.S. National Library of Medicine, soluble fiber interacts with water in your gut to create a gel-like substance that slows digestion, and is found in nuts, seeds, beans, oat bran, and some fruits and vegetables. Insoluble fiber, which doesn’t dissolve in water, adds bulk to stool and seems to help food pass more quickly through the gut; it’s found in wheat bran, vegetables, and whole grains.

But fiber can also be broken down into a second set of categories: fermentable and nonfermentable fiber. This offers a more meaningful way to look at fiber because it focuses on how these types of fiber behave in the body, rather than how they react with water. “It’s a way of characterizing fibers based on how your gut interacts with them,” says Rudolph Bedford, M.D., gastroenterologist at Providence Saint John’s Health Center in Santa Monica, California.

“Fermentable fibers serve as fuel for gut bacteria and are metabolized into beneficial microbial products such as short-chain fatty acids, which are important for our immune function, maintaining the integrity of the intestinal barrier, and provide an energy source for cells lining the colon,” says Purna Kashyap, M.B.B.S., a gastroenterologist at Mayo Clinic in Rochester, Minnesota. Non-fermentable fibers, on the other hand, aren’t as easily broken down by gut microbes and add bulk to stool, helping to keep you regular.

“They both nurture gut health in different ways, working as a team,” says Jessica Cording, M.S., R.D., registered dietitian and author of The Little Book of Game-Changers.

How much fiber do you need?

In general, the Academy of Nutrition and Dietetics recommends having 14 grams of fiber for every 1,000 calories you consume, which translates to about 25 grams for women and 38 grams for men per day.

As of yet, “there are no specific recommendations for fermentable versus non-fermentable fiber,” points out Keri Gans, M.S., R.D., registered dietitian and author of The Small Change Diet.

How to maximize the fiber in your diet

If you want to get the most out of your fiber intake, experts say that variety is key. So if you’re getting your fiber from the same foods every day, it’s worth switching things up. “Eating a variety of fiber-containing foods will help you cover your bases,” Cording says. If you want a fiber challenge, Cording suggests aiming to eat 30 plant foods per week.

Dr. Kashyap agrees. “Studies have shown that greater diversity of plant-based foods in the diet is associated with a more diverse and resilient gut microbiome. Therefore, focusing on a wide range of fiber sources is as important as meeting daily fiber intake goals.” Dr. Kashyap suggests putting these fiber-rich foods in regular rotation in your diet:

• Oatmeal
• Wheat bran
• Fruits
• Vegetables
• Legumes
• Nuts
• Seeds
• Whole grains

This combination “will provide sufficient fermentable and non-fermentable fibers, as most plant foods contain both in varying proportions,” Dr. Kashyap says.

If you’re ramping up your fiber intake, Gans recommends going slowly and drinking plenty of water to lower the odds you’ll deal with bloating and gas along the way. Keep in mind, too, that everyone’s body handles these macronutrients differently. “The response to dietary fibers, including their effect on the gut microbiome, is highly individual,” says Heidi J. Silver, R.D., Ph.D., research professor of medicine at Vanderbilt University Medical Center.

But the bottom line is, if you’re falling short on your daily fiber intake—as most American adults are—it’s worth making an effort to change that. “The more, the better with fiber,” Dr. Bedford says.