Dietary fibers and their Importance in Health

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Department of General Medicine

Dietary fiber, also known as roughage or bulk ,are the structural part of plants and are found in all plant foods including vegetables,grains,fruits,and legumes. Most dietary fibers are polysaccharides, as are starches, but the human body is not digested.Starch is a long chain of glucose molecules linked together with alpha bonds. Fiber is a long chain of glucose molecules linked together with beta linkage. Fibre plays an important part in your digestive health and overall wellness.

Types of Fiber

There are different types of fiber.Based on their physical properties, fibers can be divided into two types

• Soluble fibers
• Insoluble fibers

Soluble fiber : Soluble fiber fiber dissolves in water to form a gel-like material and are easily digested by bacteria in the intestine.This contributes to a feeling of fullness of stomach.Soluble fibers usually slow down the rate food leaves the stomach and also help to lower the blood cholesterol and glucose levels.It may also protect against colon cancer. Soluble fiber is found in oats,peas,citrus fruits, beans, apples, carrots, psyllium and barley.

Insoluble Fiber : Insoluble fibers do not dissolve in water and  not to form gels and are less readily fermented. Insoluble fibers are mostly found in vegetables and grains,help with intestinal function. These types of fibers absorb water and swell up in the intestine,and thus providing a feeling of fullness and resulting in a larger softer stool that is rapid and easier to pass. Whole-wheat flour,nuts ,wheat bran,beans and vegetables, such as cauliflower,potatoes and green beans are good sources of insoluble fiber.

Advantages of fibre in health

Dietary fibre is mainly required to keep the digestive system healthy. It also contributes to other processes, such as stabilising the glucose and cholesterol levels. A high-fiber diet has many benefits, which include:

1. Normalizes bowel movements : Dietary fiber increases the size and weight of your stool and softens it. A bulky stool is easier to pass,there by decreasing your chance of constipation. If you have loose or  watery stools, fiber helps to harden the stool because it absorbs water and adds bulk to the stool.

2. Lowers cholesterol levels : When blood cholesterol levels are high, fatty plaques and streaks  are  settled along the walls of arteries. This make the blood vessel dangerously narrow and lead to an increased risk of coronary heart disease. Soluble fibre decreases the  blood cholesterol by binding bile acids and then excreting them. Soluble fiber found in beans,flaxseed, oats and oat bran may help to lower  the total blood cholesterol levels by lowering low-density lipoprotein, or "bad," cholesterol levels. Different studies also shown that high-fiber foods may have other heart-health advantages,such as reducing bloodpressure and inflammation.

3. Fibre and ageing  : Fibre is more important for older people.The digestive system slows down with age, so a high-fibre diet becomes more important.

4. Helps control blood sugar levels : For people with diabetes,eating fibre rich diet lowers the  glucose absorption from the small intestine into the blood. A healthy diet that  contains insoluble fiber may also decrease the risk of developing type 2 diabetes.

5. Weight control : Fibre rich diet is protective against weight gain.High-fibre foods tend to have a lower energy density, which means they  give fewer kilojoules per gram of food. As a result, a person on a high-fibre diet can consume the same amount of food, but with fewer calories.Carbohydrates foods tend to be low in fat and added sugars which can help the weight management by providing fewer calories.
6. Helps maintain bowel health : Fiber rich diet may decrease the risk of developing hemorrhoids and small pouches in your colon (diverticular disease). Some fibers are fermented in the colon.This may play a important role in preventing diseases of the colon.
7. Protection against cancer of the large intestine : Dietary fibre prevents the accumulation of cancer-causing (or carcinogenic) materials because it lowers the retention period of waste materials.

Daily dietary fibre requirement

Disorders that can arise from a low-fibre diet include:

• Constipation
• Irritable bowel syndrome
• Diverticulitis
• Heart disease
• Some cancers

Food Sources of Fiber

Foods are the principal source of fiber, get both soluble and insoluble fiber. Food sources of fiber include;

• Beans, peas and other legumes
• Fruits
• Whole-grain products
• Nuts and seeds

Refined or processed foods — such as pulp-free juices,canned fruits and vegetables,white breads and pastas, and non-whole-grain cereals — are lower in fiber. The grain-refining process , separate the outer coat (bran) from the grain, which lowers its fiber content.

How much fibre do we need?

Most people do not eat    sufficient dietary fibre. For adults,the recommended average intake for dietary fibre is 18g per day.Children need proportionately less.

Young children are advised against consuming too much dietary fibre as it can make it too bulky.  This may make them  full before they have eaten enough food to give them the vitamins, minerals and the energy they need.

High-fiber foods are good for your health.But adding too much fiber too quickly can promote abdominal bloating ,intestinal gas,and cramping.Increase fiber in your diet gradually over a period of a few weeks. It allows the natural bacteria in your digestive system to adjust to the change.

Reference:

• Fiber ; From Wikipedia, the free encyclopedia.
• Dietary Fiber ; College Of Agriculture And Life Sciences ; by Scottie Misner, Evelyn Whitmer and Traci Armstrong Florian.
• Why is fibre important? From NHS Choices.
• Fibre in food ; Better Health Channel.
• The importance of Fibre ; Goodness Superfoods.
• Healthy Lifestyle Nutrition and healthy eating ;Mayo Clinic.
• Why you need fibre ; Body+Soul.
• Total Dietary Fiber; Medallion Laboratories Analytical Progress  By Jonathan W. DeVries, Ph.D.