What Is Fiber?

Fiber is a term used to describe carbohydrates from plant foods (such as fruits, vegetables, grains, nuts, seeds and legumes) that the body cannot digest and use for energy. Fiber offers a number of health benefits, and the average American does not meet the daily recommended amounts.There are two main types of fiber, known as soluble and insoluble fiber. As their names suggest, soluble fiber dissolves in water, forming a gel, while insoluble fiber does not. 

Due to the unique properties of soluble fiber, this type of fiber may be recommended to improve both diarrhea and constipation. Soluble fiber absorbs water in the GI tract, forming a spongy or gummy gel, which in turn slows down digestion. This delay can prevent diarrhea or urgency. Since soluble fiber absorbs water, it also has the ability to improve stool consistency by keeping bowel movement soft (for those struggling with constipation) and formed (for those struggling with diarrhea). Soluble fiber is often found in the flesh of certain fruits/vegetables and in some grains. 

Insoluble fiber does not dissolve in water, traveling through the digestive tract relatively intact. The bulkiness of insoluble fiber has a stimulating effect on the GI tract, speeding up the passage of content through the gut and adding bulk to the stool. Insoluble fiber is often found in the skins and seeds of fruits/vegetables and in the outer layer (or the bran) of grains. 

As part of your nutrition care plan, your dietitian may recommend an increase in total fiber, an increase in a specific type of fiber, or in some instances, a reduction in a specific type of fiber. Work with your dietitian to determine what your specific fiber needs are, then use the tables below to help you reach your goals.

Foods High in Soluble Fiber

Food Serving Amount (g) fiber per serving 
Oatmeal/Oat Bran  ½ cup 2 g 
Barley ½ cup 3 g 
Quinoa ½ c 5 g 
Potato/Yam/Sweet Potato (no skin) 1 medium2 g 
Carrots ½ c 2 g
Parsnip½ c 3.5 g 
Pumpkin½ c 3.5 g
Squash, winter & summer½ c 3.5 g 
Beets ½ c 2 g 
Turnips 1 medium2 g
Peeled apple1 medium2.5 g 
Orange 1 medium3 g 
Pear (contains soluble & insoluble)1 medium5 g 
Banana 1 medium3 g 
Avocado¼ medium3 g 
Cantaloupe1 c 1.5 g 
Chia Seeds 1 Tbsp5 g 
Lentils½ c 8 g 
Beans ½ c 5-9 g 
Peas, canned ½ c 3.5 g 

Foods High in Insoluble Fiber

Food ItemServing Amount (g) fiber per serving 
Whole wheat bread 1 slice 2 g (can vary by brand) 
Whole wheat pasta ½ c 3 g
Whole wheat cereals ½ c 2-4 g 
Popcorn2 c 2.5 g
Lettuce 1 c <1 g
Spinach, raw 1 c <1 g 
Spinach, frozen½ c 3.5 g 
Kale, raw 1 c <1 g 
Kale, cooked½ c 1.5 g 
Cabbage ½ c 1.5 g 
Corn½ c 2 g 
Apple with peel1 medium3.5 g 
Berries (also contain soluble)½ c 2-4 g 
Kiwi (also contains soluble)1 fruit 2.5 g 
Grapes 1 c 1 g 
Raisins¼ c 1.5 g 
Flaxseed, ground  (also contains soluble)1 Tbsp2 g