scorecardThe differences between soluble fiber and insoluble fiber and why both are equally important for your health
  1. Home
  2. Science
  3. Health
  4. news
  5. The differences between soluble fiber and insoluble fiber and why both are equally important for your health

The differences between soluble fiber and insoluble fiber and why both are equally important for your health

Carla Delgado,David Seres   

The differences between soluble fiber and insoluble fiber and why both are equally important for your health
LifeScience5 min read
Soluble and insoluble fiber both improve gut health and digestion    pixelfit/ Getty Images
  • Soluble and insoluble fiber are equally important for your health and one is no better than the other for general well-being.
  • Soluble fiber dissolves and ferments in your gut which provides important nutrients for your microbiome and may help you maintain healthy blood sugar and cholesterol levels.
  • Insoluble fiber moves through the digestive tract intact and research shows that it may help with weight loss, improved bowel function, and reduce the risk of colorectal cancer.

The difference between soluble and insoluble fiber is often confusing. Although both are important for metabolic health, the main distinction boils down to how well they dissolve in water. But that doesn't mean one is more important than the other.

"We need both soluble and insoluble fiber in our diet," according to Anne E. Linge, RDN, CD, CDE, Dietitian from the University of Washington Medical Center Nutrition Clinic. "Most foods supply both."

Here's what you should know about the differences between soluble and insoluble fiber, their health benefits, and how you can incorporate them into your diet.

Soluble fiber vs. insoluble fiber

The difference between soluble and insoluble fiber is how well each dissolves and ferments in the gastrointestinal tract.

Dietary fiber, in general, is a type of carbohydrate that the body cannot digest. Once it hits your stomach, it moves through your digestive tract, pulling water into the intestines as it goes. This adds bulk to the stool to help prevent constipation, but it also slows down digestion which can stabilize blood sugar levels after a meal.

Certain soluble fibers, like psyllium, form a viscous gel as they move through the digestive tract that can also help with diarrhea. Moreover, soluble fiber tends to be more fermentable than insoluble fiber, making it a meal to sustain the healthy bacteria that colonize your intestine and provide nourishment for your colon.

Both types of fiber are equally essential and are of nutritional importance, providing significant benefits to your digestive health.

Health benefits of dietary fiber

Be wary of claims that dietary fiber alone can cure gastrointestinal conditions like ulcerative colitis or directly cause weight loss, says_Elisabetta Politi, MPH, RD, LDN, CDCES, Dietitian Clinician at the Duke Diet & Fitness Center.

Here are scientifically-proven health benefits of getting enough dietary fiber in your diet:

  • Possibly reduces the risk of colorectal cancers: Insoluble fiber balances intestinal pH and reduced the time it takes food to move through your gut, which may reduce the risk of carcinogen formation in the gut wall, though more research is needed.
  • Controls blood sugar levels: Soluble fiber can slow the absorption of glucose and insoluble fiber may reduce the risk of type two diabetes.
  • Improves bowel movements: Insoluble fiber acts like a sponge by pulling water into the stool, effectively making it easier to pass.
  • Lowers cholesterol levels: Soluble fiber helps lower the total and low-density lipoprotein cholesterol, which may reduce the risk of heart disease.
  • Helps manage weight: Insoluble fiber supplementation is associated with significant weight loss, but only when it is combined with calorie reduction and increased physical activity.

To reap the many benefits that dietary fiber has to offer, it is best to eat a variety of foods that are rich in both soluble and insoluble fiber.

Good sources of soluble and insoluble fiber

The Westernized diet, one that is low in fiber and high in sucrose and saturated fats, is currently a growing health risk that is strongly associated with the increase in the prevalence of metabolic diseases. Most people often consume only half of the recommended daily fiber intake, so it is crucial to be aware of the amount that you need per day.

Here is the current daily recommended amount for dietary fiber:

Age/GenderRecommended daily fiber
Children 1-3 years old19 grams
Children 4-8 years old25 grams
Girls 9-18 years old26 grams
Boys 9-13 years old31 grams
Boys 14-18 years old38 grams
Women 19-50 years old25 grams
Men 19-50 years old38 grams
Women 51+ years old21 grams
Men 51+ years old31 grams

Politi recommends reading the nutrition facts label at the grocery store to check and compare the amount of dietary fiber in various products. Here are ten foods rich in soluble and insoluble fiber:

Sources of soluble fiberSources of insoluble fiber
AvocadoRaw coconuts
BroccoliDry roasted peanuts
Rye breadSesame seeds
Green beansBitter gourd
CarrotsRaw white beans
GuavaRaw lentils
All-purpose bleached flourOats
Wheat breadWhole grain wheat
Red kidney beansBeetroot

Politi prefers getting fiber from whole foods first, but a fiber supplement may also help in reaching the required daily intake.

Keep in mind that some supplements aren't suitable for people with certain allergies or medical conditions. People with diabetes should opt for flavorless and sugar-free supplements, while people with celiac disease must choose gluten-free fiber like psyllium. Here are some common brands of fiber supplements:

  • Metamucil is made from psyllium, which contains 70% soluble fiber and 30% insoluble fiber.
  • Benefiber contains wheat dextrin, a great source of soluble fiber.
  • Citrucel's active ingredient is methylcellulose, which is mainly insoluble fiber.
  • Konsyl is also made from psyllium and contains both soluble and insoluble fiber.

"Increasing your fiber intake too quickly can lead to gas and bloating," says Linge. Add fiber to your diet gradually over several weeks so the digestive system can adjust better.

Insider's takeaway

Dietary fiber, both soluble and insoluble, is essential to a healthy diet and can provide plenty of health benefits including a reduced risk of colorectal cancers, blood sugar control, and improved bowel movements.

There are numerous fiber-rich foods, but if you aren't meeting the daily recommended fiber intake, you can consider taking fiber supplements. "Remember also to drink enough water as you increase your fiber intake," says Linge.

Related stories about diet and nutrition: