Fiber in the Kidney Diet

People with chronic kidney disease (CKD) and those on dialysis who stick with a kidney-friendly diet may find it tough to add fiber into their restrictive meal plan. Take a look at what fiber is, why it is important for people with kidney disease and how you can add it to your kidney-friendly diet.

What is fiber?

Dietary fiber is defined as the component of carbohydrate that cannot be digested by enzymes in the human small intestine. Fiber provides structure for plant cells. It is found in all types of plants – fruits, vegetables, grains, legumes and nuts. Unlike fats, carbohydrates and proteins, fiber cannot be broken down or absorbed when passing through your digestive system.

What does fiber do?

There are two different types of fiber: soluble and insoluble. Your body needs both kinds of fiber.

Soluble fiber is fiber that dissolves in water. Soluble fiber absorbs fluid as it passes through the digestive system, creating softer, larger stools. Food sources of soluble fiber include oat bran, apples, oranges, berries and various vegetables. The psyllium (part of a plant) found in supplements such as Metamucil®, Citrucel® and Fiberall® is also soluble fiber.

Insoluble fiber (roughage) is fiber that does not dissolve in water. Insoluble fiber absorbs water, makes stool bulkier to help bowel movements pass more easily. Examples of insoluble fiber foods are barley, corn, rice, bran, whole wheat, vegetables and apple and pear skins.

Fiber health benefits for people with kidney disease

Here are some reasons why adequate fiber intake in the kidney diet can be beneficial to people with chronic kidney disease.

  • Keeps GI (gastrointestinal) function healthy
  • Adds bulk to stool to prevent constipation
  • Prevents diverticulosis (diverticular disease; pockets inside the colon)
  • Helps increase water in stool for easier bowel movements
  • Promotes regularity
  • Prevents hemorrhoids
  • Soluble fiber from fruits, oats, legumes and barley helps control blood sugar and cholesterol

How much fiber does a person need?

The average American diet contains only 5 to 15 grams of fiber a day. That is considerably below the 14 grams of fiber for every 1,000 calories you consume, as recommended by the US Dietary Guidelines. The Food and Nutrition Board suggests 25 grams of fiber a day for women and 38 grams of fiber a day for men under the age of 50. For people over 50 years of age, women should get 21 grams of fiber a day and men should get 30 grams of fiber a day in their diet. If you are following a low potassium, low phosphorus plan, fiber intake may be even more difficult to include in your kidney diet.

Gradually adding fiber to the kidney diet

Many people with chronic kidney disease do not get enough fiber, because many of the best fiber sources are too high in potassium and phosphorus. When making diet changes to increase fiber intake be aware that sudden, dramatic increase of fiber can cause gas, bloating and cramps. Fiber should be increased gradually and fluid intake may need to be adjusted. Talk to your dietitian or doctor about how to slowly increase fiber into your CKD diet.

Good fiber food choices for the kidney diet

For people on a kidney-friendly diet, eating foods lower in potassium and phosphorus may be necessary to keep these minerals in the normal range. In recent years more research has led to a less restrictive diet with natural whole grain products, considering that only 40 to 60% of naturally occuring organic phosphorus is absorbed. Be aware of portion control; 1/2 cup is the suggested serving size for most of these foods. These are the best high fiber fruits and vegetables for people with chronic kidney disease:

  • Apple, unpeeled
  • Apricot
  • Asparagus
  • Beets
  • Blackberries
  • Blueberries
  • Broccoli
  • Brussels sprouts
  • Cabbage, raw
  • Carrots
  • Cauliflower
  • Celery
  • Cherries
  • Collard greens
  • Cooked grits
  • Corn
  • Pineapple, raw
  • Eggplant
  • Figs
  • Fruit cocktail
  • Grapefruit
  • Grape-Nuts Flakes®
  • Green beans
  • Green peas
  • High fiber white bread
  • Lettuce
  • Mustard greens, cooked
  • Okra
  • Onion
  • Peach
  • Pear, unpeeled
  • Plums
  • Raspberries
  • Strawberries
  • Summer squash
  • Tangerines

Tips to increase fiber in the kidney diet

  • Have regular meal times so you know when you get fiber and from what.
  • Eat all the allowed servings of kidney-friendly fruits and vegetables suggested by your meal plan.
  • Eat peelings on fruit and vegetables when reasonable.
  • Snack on unsalted popcorn and raw vegetables.
  • Use high fiber white bread, whole wheat or whole grain bread, rye bread or oatmeal bread.
  • Include a breakfast cereal with fiber (one that is approved by your dietitian and is low in potassium and phosphorus).
  • Eat whole fruit instead of drinking juice.
  • Try fiber supplements, such as Unifiber® or FiberSure®. These can be purchased without a prescription, but be sure to let your doctor and dietitian know if yo use a supplement. Ask your renal dietitian how to incorporate these products into your plan.

Constipation in people with chronic kidney disease

Sometimes fiber is not enough to relieve constipation. Here are suggestions on what to do when fiber intake is too little:

  • Increase your activity level. Daily physical activity helps to regulate the bowels. Try a daily walk, stretching exercises, light housework or light gardening.
  • Use part of your fluid allowance as a warm beverage first thing in the morning or before going to bed at night; warm lemonade, tea or coffee (drink decaf at night) work well.
  • No matter how busy you are, always respond to your bathroom urges.
  • If possible, avoid long-term use of laxatives and stool softeners.
  • Check with your nurse or doctor about a laxative, stool softener or fiber supplement for people on dialysis. Avoid milk of magnesium, Correctol®, epsom salts and mineral oil.
  • Add 1 tablespoon of dark Karo® syrup to 1/2 cup of applesauce. This helps increase the amount of water in the gut to make bowel movements easier. Avoid this remedy if you have diabetes. Karo syrup is a very concentrated carbohydrate that will cause blood sugar levels to soar.

The amount of fiber needed to relieve constipation varies from person to person. Instead of worrying about eating a particular number of grams of fiber, concentrate on making small, gradual changes to your eating plan to increase fiber intake.

Recipes high in fiber

The following are recipes high in fiber and can be found at


Fiber in the kidney diet is important. Yet getting enough fiber can be a challenge as some high fiber fruits, vegetables and grains are limited or restricted in the kidney diet due to their higher potassium or phosphorus level compared to other foods in these groups. Fiber can help regulate your digestive system, may halt constipation and introduce more kidney-friendly fruits and vegetables into your diet. Try some of the suggestions in this article and talk to your dietitian about how you can add fiber into your kidney-friendly diet.

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