High-fiber foods tend to have a lower glycemic index than refined carb sources, which have been stripped of most of their fiber.

However, scientists believe only high-viscosity, soluble fibers have this property (20Trusted Source).

Including these viscous, soluble fibers in your carb-containing meals may cause smaller spikes in blood sugar (21Trusted Source).

This is important, especially if you’re following a high-carb diet. In this case, the fiber can reduce the likelihood of the carbs raising your blood sugar to harmful levels.

That said, if you have blood sugar issues, you should consider reducing your carb intake, especially low-fiber, refined carbs, such as white flour and added sugar.

SUMMARY

Foods that contain viscous fiber have a lower glycemic index and cause smaller spikes in blood sugar than foods that are low in fiber.

Viscous, soluble fiber can also reduce your cholesterol levels.

However, the effect isn’t nearly as impressive as you might expect.

A review of 67 controlled studies found that consuming 2–10 grams of soluble fiber per day reduced total cholesterol by only 1.7 mg/dl and LDL cholesterol by 2.2 mg/dl, on average (22Trusted Source).

But this also depends on the viscosity of the fiber. Some studies have found impressive reductions in cholesterol with increased fiber intake (23Trusted Source, 24Trusted Source).

Whether this has any meaningful effects in the long term is unknown, although many observational studies show that people who eat more fiber have a lower risk of heart disease (25Trusted Source).

SUMMARY

Some types of fiber can reduce cholesterol levels. However, most studies show that the effect isn’t very large, on average.

One of the main benefits of increasing fiber intake is reduced constipation.

Fiber is claimed to help absorb water, increase the bulk of your stool and speed up the movement of your stool through the intestine. However, the evidence is fairly conflicting (26, 27Trusted Source).

Some studies show that increasing fiber can improve symptoms of constipation, but other studies show that removing fiber improves constipation. The effects depend on the type of fiber.

In one study in 63 individuals with chronic constipation, going on a low-fiber diet fixed their problem. The individuals who remained on a high-fiber diet saw no improvement (28Trusted Source).

In general, fiber that increases the water content of your stool has a laxative effect, while fiber that adds to the dry mass of stool without increasing its water content may have a constipating effect.

Soluble fibers that form a gel in the digestive tract and are not fermented by gut bacteria are often effective. A good example of a gel-forming fiber is psyllium (29Trusted Source).

Other types of fiber, such as sorbitol, have a laxative effect by drawing water into the colon. Prunes are a good source of sorbitol (30Trusted Source, 31Trusted Source).

Choosing the right type of fiber may help your constipation, but taking the wrong supplements can do the opposite.

For this reason, you should consult with a health professional before taking fiber supplements for constipation.

SUMMARY

The laxative effects of fiber differ. Some reduce constipation, but others increase constipation. This appears to depend on the individual and type of fiber.

Colorectal cancer is the third leading cause of cancer deaths in the world (32Trusted Source).

Many studies have linked a high intake of fiber-rich foods with a reduced risk of colon cancer (33Trusted Source).

However, whole, high-fiber foods like fruits, vegetables and whole grains contain various other healthy nutrients and antioxidants that may affect cancer risk.

Therefore, it’s difficult to isolate the effects of fiber from other factors in healthy, whole-food diets. To date, no strong evidence proves that fiber has cancer-preventive effects (34Trusted Source).

Yet, since fiber may help keep the colon wall healthy, many scientists believe that fiber plays an important role (35Trusted Source).

SUMMARY

Studies have associated a high fiber intake with a reduced risk of colon cancer. However, correlation doesn’t equal causation. To date, no studies have proven the direct benefits of fiber in cancer prevention.

Dietary fiber has various health benefits.

Not only does it feed your gut bacteria, fermentable fiber also forms short-chain fatty acids, which nourish the colon wall.

Additionally, viscous, soluble fiber may reduce your appetite, lower cholesterol levels and decrease the rise in blood sugar after high-carb meals.

If you are aiming for a healthy lifestyle, you should make sure to get a variety of fiber from whole fruits, vegetables and grains.