Dietary Fibers: Non-Starch Polysaccharides

What are Dietary Fibers and why do we need them?

Dietary fiber, also known as Non-starch polysaccharides (NSPs) or roughage, is a type of carbohydrate that cannot be digested by the human body. 

What is Dietary Fiber?

Dietary fiber or Non-starch polysaccharides (NSPs), is a type of complex carbohydrate that is found in plant-based foods such as fruits, vegetables, legumes, whole grains, nuts, and seeds. Unlike other types of carbohydrates, dietary fiber cannot be broken down by the digestive enzymes in our body, meaning it passes through the digestive tract largely unchanged.

Dietary fiber can be divided into two categories: soluble and insoluble fiber. Soluble fiber dissolves in water and forms a gel-like substance that can help regulate blood sugar levels and lower cholesterol. Insoluble fiber, on the other hand, does not dissolve in water and helps to promote regular bowel movements.

Soluble Fiber

Soluble fiber dissolves in water to form a gel-like substance that can help regulate blood sugar levels, lower cholesterol levels, and promote feelings of fullness. It is found in foods such as oats, barley, beans, lentils, and some fruits and vegetables.

When soluble fiber enters the digestive tract, it binds with water to form a viscous gel. This gel slows down the digestive process, which can help regulate the absorption of nutrients and prevent spikes in blood sugar levels. Soluble fiber also binds with bile acids in the small intestine, which helps to reduce the levels of cholesterol in the blood. This, in turn, can lower the risk of heart disease.

Read more: What are soluble dietary fibers?

Insoluble Fiber

Insoluble fiber, on the other hand, does not dissolve in water and adds bulk to the stool. It is found in foods such as whole grains, nuts, seeds, and the skin and seeds of some fruits and vegetables.

When insoluble fiber enters the digestive tract, it absorbs water and adds bulk to the stool, which helps to promote regular bowel movements and prevent constipation. Insoluble fiber also helps to support a healthy gut microbiome by providing food for beneficial bacteria in the colon.

Read more: What are insoluble fibers?

What are the different types of Dietary fiber?

There are several types of dietary fibers or Non-starch polysaccharides (NSPs), each with its unique properties and health benefits. 

The main types of NSPs are:

• Cellulose, 

• Hemicellulose, 

• Pectin, 

• Gums 

Cellulose is the most common type of NSP and is found in the cell walls of plants. It is indigestible by humans and provides bulk to the diet, helping to promote regular bowel movements and prevent constipation.

Hemicellulose is also found in plant cell walls and is composed of a variety of sugars. It is partially digestible by humans and can help to regulate blood sugar levels.

Pectin is found in the cell walls of fruits and vegetables and is a type of soluble fiber. It helps to lower cholesterol levels and can also help to regulate blood sugar levels.

None of these NSPs are digested by gut enzymes. However, NSPs are partly broken down in the gastrointestinal tract, mainly by colonic bacteria, producing gas and volatile fatty acids, e.g. butyrate.

Sources of Dietary Fibers (Non-starch polysaccharides)

Dietary fiber is obtainable from several sources, namely fruits, vegetables, whole grains, legumes, nuts, and seeds. Notably, fruits, such as apples, bananas, oranges, and berries, are rich in fiber, as are vegetables, including broccoli, carrots, sweet potatoes, and leafy greens. Additionally, whole grains, such as whole wheat bread, brown rice, and quinoa, provide high quantities of fiber, alongside other vital nutrients. Legumes, such as beans, lentils, and peas, also represent excellent sources of fiber. Lastly, nuts and seeds, such as almonds, chia seeds, and flaxseeds, are good sources of both soluble and insoluble fiber.

Processing plants/foods destroy dietary fibers. It is therefore important to consume unprocessed food such as bran, the fiber from wheat.

In addition to these whole food sources, there are also fiber supplements available, such as psyllium husk and inulin. However, it is always recommended to get fiber from whole foods rather than supplements as whole foods provide additional nutrients and health benefits beyond just fiber.

Functions of Dietary Fibres

One of the most important functions of dietary fiber is to promote regular bowel movements and prevent constipation. Fiber absorbs water in the gut, which helps to soften stools and make them easier to pass. This can help to prevent conditions such as hemorrhoids, diverticulitis, and colon cancer.

Another benefit of dietary fiber is that it can help to lower cholesterol levels. Soluble fiber, which is found in foods such as oats, barley, and fruits, can bind with cholesterol and bile acids in the gut and remove them from the body. This can help to reduce the risk of heart disease and stroke.

Fiber also has a role in weight management, it makes you feel full and satisfied after eating, slows down digestion, and reduces the absorption of sugar and fat. This can help to regulate blood sugar levels and control appetite, which can lead to weight loss and a reduced risk of obesity and related diseases.

Dietary fiber can also help to improve the health of the gut microbiome. A diet that is high in fiber can promote the growth of beneficial bacteria in the gut, which can improve overall health and reduce the risk of certain diseases.

Recommended Daily Intake for Dietary Fibers

The recommended daily intake of dietary fiber for adults is 25 grams for women and 38 grams for men. However, most people do not consume enough fiber in their diet. To increase fiber intake, it is recommended to eat more fruits, vegetables, whole grains, nuts, and seeds, and to choose foods that are high in fiber such as beans, lentils, and chickpeas.

Dietary fiber is an essential nutrient that plays a crucial role in maintaining good health. A diet that is high in fiber can help to promote regular bowel movements, lower cholesterol levels, regulate blood sugar levels, control appetite, and improve the health of the gut microbiome.