Difference Between Dietary Fiber and Soluble Fiber

Main Difference – Dietary fiber vs Soluble Fiber

The edible portion of the cell walls in plants is called dietary fibers. It is resistant to digestion. Dietary fibers are one of the essential parts of the diet. Dietary fibers can be categorized into two groups as soluble fibers and insoluble fibers. Generally, the fiber intake for adults should be 20-35 g per day. This amount should come from a combination of both soluble and insoluble fibers. Neither soluble nor insoluble fibers are absorbed by the body. The main difference between dietary fiber and soluble fiber is that dietary fiber is the indigestible portion of the diet whereas soluble fiber is a type of fiber that is partially soluble in water. Insoluble fiber does not dissolve in water and is not absorbed by the body.

Key Areas Covered

1. What is Dietary Fiber
      – Definition, Benefits, Examples
2. What is Soluble Fiber
      – Definition, Benefits, Examples
3. What are the Similarities Between Dietary Fiber and Soluble Fiber
      – Outline of Common Features
4. What is the Difference Between Dietary Fiber and Soluble Fiber
     – Comparison of Key Differences

Key Terms: Bowel Movement, Cholesterol Levels, Dietary Fiber, Insoluble Fiber, Soluble Fiber, Type 2 Diabetes, Weight Loss

What is Dietary Fiber

Dietary fiber is the edible portions of the cell wall in plants. Since it is resistant to digestion, dietary fiber is an extremely beneficial component of diets. Dietary fibers reduce the intake of food in meals. Therefore, they are important for weight loss. The food that is rich in fibers takes a long time to digest. This results in the feeling of fullness. The slowness of the absorption, which is caused by the fibers in the food may also slow the absorption of glucose into the bloodstream. Therefore, dietary fibers prevent an increased level of blood glucose. Whole grains, nuts, legumes, fruits, and vegetables are the foods that contain dietary fibers.

Figure 1: Food with Dietary Fibers

The two types of dietary fibers are soluble and insoluble fibers. Recommended fiber intake per day for adults is 20 – 35 g. This amount should be a combination of both soluble and insoluble fibers. Generally, the insoluble to soluble ratio should be 3:1. Both soluble and insoluble fibers do not dissolve in water. But, they have different properties. Only soluble fibers are partially soluble in water. Insoluble fibers do not dissolve in water. Hence, they pass through the digestive system in its original form. Insoluble fibers prevent constipation and the occurrence of hemorrhoids. They also balance the pH of the intestine. Lignin, cellulose, and hemicellulose are types of insoluble fibers. Bran layers of the cereal grains contain most insoluble fibers. 

What is Soluble Fiber

The soluble portion of the dietary fibers is referred to as the soluble fiber. Soluble fibers are partially soluble in water. They swell to produce a gel-like substance. Heart protection and diabetes protection are the two major benefits of the soluble fiber. Soluble fibers attach and take out the cholesterol in the digestive system. The lowering of the cholesterol in the body reduces the risk of heart disease. Oatmeal is one of the most important types of soluble fiber which reduces the cholesterol levels. Due to the slowness of absorption, soluble fibers do not cause spikes in the blood glucose levels. Therefore, soluble fibers lower the risk of type 2 diabetes. Oats, barley, legumes such as beans, peas, and lentils, fruits like oranges and apples, and vegetables such as carrots contain soluble fibers. Oatmeal is shown in figure 2.

Figure 2: Oatmeal

Soluble fibers also help weight loss and healthy bowel movement. Inulin oligofructose, beta-glucans, mucilage, polydextrose polyols, some pectins, gum, psyllium, wheat dextrin, and resistant starch are types of soluble fibers.

Similarities Between Dietary Fiber and Soluble Fiber

• Both dietary fiber and soluble fiber are two types of fibers obtained from the diet.
• Both dietary fiber and soluble fiber are an essential part of the diet.
• Both dietary fiber and soluble fiber do not dissolve in water.
• Both dietary and soluble fiber do not absorb by the body.
• Both dietary fiber and soluble fiber are important in weight loss and increased bowel movement.

Difference Between Dietary Fiber and Soluble Fiber

Definition

Dietary Fiber: Dietary fiber is the edible portion of the cell walls in plants.

Soluble Fiber: Soluble fiber is the soluble portion of dietary fibers.

Correlation

Dietary Fiber: Dietary fiber is a type of indigestible fiber in the diet.

Soluble Fiber: Soluble fiber is a type of dietary fiber.

Solubility

Dietary Fiber: Some dietary fibers are insoluble in water.

Soluble Fiber: Soluble fibers are partially water-soluble.

Types

Dietary Fiber: Lignin, cellulose, and hemicellulose are types of insoluble fibers.

Soluble Fiber: Inulin oligofructose, beta-glucans, mucilage, polydextrose polyols, some pectins, gum, psyllium, wheat dextrin, and resistant starch are types of soluble fibers.

Benefits

Dietary Fiber: Dietary fibers cause weight loss, and prevent glucose spikes.

Soluble Fiber: Soluble fibers lower the bad cholesterol level in the body.

Foods

Dietary Fiber: Whole grains, fruits, and vegetables contain dietary fibers.

Soluble Fiber: Oats, nuts, seeds, fruits such as apples, pears, strawberries, and blueberries, and legumes such as beans, lentils, and split peas are examples of food containing soluble fibers. 

Conclusion

Dietary fiber and soluble fiber are two types of fibers in the food. Dietary fibers are indigestible by the body. Soluble fibers and insoluble fibers are the two types of dietary fibers. Soluble fibers partially dissolve in water to produce a gel-like substance. Both dietary fibers and soluble fibers play a major role in weight loss and reducing diabetes. The main difference between dietary fiber and soluble fiber is the solubility of each type of fiber in water.

Reference:

1. “Types of Fiber and Their Health Benefits.” WebMD, Available here.

Image Courtesy:

1. “Fruit, Vegetables and Grain NCI Visuals Online” released by the National Cancer Institute (Public Domain) via Commons Wikimedia
2. “Oatmeal, Part 2” by Rachel Hathaway (CC BY 2.0) via Flickr