What is the Difference Between Soluble and Insoluble Fiber?

Soluble and insoluble fiber play different roles in promoting health and preventing disease. Find out what do they do and which foods contain them.

Monica Reinagel, MS, LD/N, CNS
5-minute read
Episode #93

What Foods Contain Insoluble Fiber?

The best food sources of insoluble fiber include:

  • wheat

  • corn

  • oat bran

One of the reasons that you’re encouraged to eat whole grains is because they include the bran and are therefore higher in fiber than refined grains.

Other good sources of insoluble fiber include:

  • nuts

  • flaxseed

  • the skins and peels of many fruits and vegetables, such as apples and potatoes

But the truth is that most foods contain a mixture of soluble and insoluble fiber. The inside of apples, for example, provide soluble fiber and the skins are mostly insoluble fiber.

How Much Soluble and Insoluble Fiber Do You Need?

The dietary recommendations for fiber are 25 gram per day for women and 38 grams per day for men. There is no guideline for how much of that should be soluble or insoluble. In the average diet, about three-quarters of the fiber is insoluble and one quarter is soluble. I think that reflects the fact that we tend to eat a lot of grain-based foods and not enough fruits and vegetables. 

Which Type of Fiber Should You Eat?

If you’re particularly concerned with keeping your blood sugar steady or your cholesterol down, you might want to focus on eating more legumes and oats, which are good sources of soluble fiber. If digestive health or constipation is a problem, you might want to emphasize foods that contain a lot of insoluble fiber, such as flaxseed, wheat, corn, and rice bran. But chances are you could do with more of both kinds of fiber. Most people get less than half the recommended amount.

Should You Take Fiber Supplements?

I suggest that you get most or all of your fiber from actual foods instead of fiber supplements, because high fiber foods contain a lot of other healthy nutrients as well.

And it’s not that hard to do.  For example, you’ll get a third of your fiber needs by eating the recommended five servings of vegetables and two to three servings of fruit (not juice!) each day. Four servings of whole grains provide another third. Three or four servings of nuts, seeds, or legumes will take you over the finish line—with a nice mix of soluble and insoluble fiber.

If you have a nutrition question for me, send an email to nutrition@quickanddirtytips.com or post it on my Nutrition Diva Facebook Page. If tweeting is more your thing, I also have a handy little Twitter account. 

You can also search the archives using the search box at the top of the page. There’s a good chance I might have already answered your question in a previous article.

Have a great week and remember to eat something good for me!

Fiber image courtesy of Shutterstock


About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.