The Health Benefits of Dietary Fiber

The Health Benefits of Dietary Fiber


What is fiber?

Roughly speaking, dietary fiber is the part of plants that is indigestible. It is sometimes called roughage or bulk. When I say indigestible, I mean that your body either does not have the natural enzymes to break the plant components down or that the transit time in our body is too fast for us to break it down (some animals have slower transit times and more stomachs).

The contents vary widely from plant-to-plant but include substances like lignin (part of a plant cell wall) and polysaccharides  and oligosaccharides (refers to various types of carbohydrates but in this case things like cellulose and inulin), and certain starches that we can’t digest. Basically, the fiber gets through your entire gastrointestinal tract without any substantial changes in its composition (although it certainly looks different!) This is significant because it it can modify the landscape of our GI tract and also affect how various other foods are absorbed.


Diets high in fiber have have been shown to have a variety of health benefits.

  • Normalize bowel movements. Increases weight, size and softens stool. It can help with both constipation and can harden up loose stools. If you suffer from either problem it will pull you back towards the middle, normalizing your bowel movements.
  • Maintain bowel health. High fiber diets reduce risk of hemorrhoid and diverticular disease which can lead to diverticulitis.
  • Lowers cholesterol levels. Soluble fibers appear to help inhibit your body’s absorption of certain bad fats such as LDL (low-density lipoprotein) which have been linked to increased risk of heart attack, stroke and dementia.
  • Control blood sugar levels. In diabetics, soluble fiber has been shown to help slow the absorption of sugar and help maintain lower blood sugar levels. It may also help reduce the risk of developing type 2 diabetes.
  • Healthy weight. High fiber diets are more filling, so you are likely to eat less food. They are also less energy dense, meaning fewer calories in the same volume of food.

Although better research is needed, high fiber diets may also help with:

  • Lowering blood pressure (hypertension)
  • Anti-inflammatory processes
  • Colorectal cancer (the evidence is mixed at this time)


Before I talk about sources, I need to quickly review the two types.

The first is soluble, meaning it will dissolve in water in your GI tract and form a gel-like substance in your gut. Soluble fiber appears to help more with lowering cholesterol and blood sugar.

The second type is non-soluble meaning it does not dissolve in water and promotes movement of material through your gut. Non-soluble appears to help more with having an overall healthy digestive tract and treating constipation.

While most plant based foods contain a combination of both soluble and insoluble fiber, the specific content varies widely from food to food.

Best Sources

  • Soluble: oats, peas, beans, apples, citrus fruits, carrots, barley and psyllium
  • Insoluble: Whole-wheat flour, wheat bran, nuts, beans and vegetables, such as cauliflower, green beans and potatoes.
  • Supplements:

Ok Sources

  • Supplements (metamucil, citrucel, fibercon) as they have less variety of fiber and are also stripped of any other nutritional content. Better than nothing but not as good as the foods above.
  • Foods with fiber added cereal, yogurt, granola bars

Bad Sources

Refined and processed foods such as canned fruits and vegetables, white breads and pastas, cereals that are not whole grain,

Recommended Daily Allowance

Institute of Medicine

  • Men:
    • Under 50 (38 grams/day),
    • Over 50 (30 grams/day)
  • Women:
    • Under 50 (25 grams/day),
    • Over 50 (21 grams/day)

Drink lots of water! Fiber works best when absorbed by water

Fiber Supplement Options

Top 10 Natural Sources of Dietary Fiber

Top 10 Natural Sources of Dietary Fiber

Does Whole Grain Consumption Lower Cholesterol?

Does Whole Grain Consumption Lower Cholesterol?