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By Dr. Keith E. Lewis
June 26, 2008

If you watch much TV, read magazines, newspapers, tabloids, you will notice that more and more we are hearing the word dietary fiber and the importance of fiber in the diet:  Fiber helps reduce weight.  Fiber helps you think more clearly.  Fiber helps reduce cancer.  Fiber helps improve bowel activity, but what is it and how does it do that, and are there different types of fiber or is there only one type of fiber? Fiber, as it relates to our diet, is a carbohydrate.

All of the parts of a plant that digestive enzymes cannot break down in our body is considered fiber.  When you eat a food high in fiber, it tends to slow down the release of sugars in food.  As a side note, it also slows down the release of certain fats in food to be absorbed by our body.  As far as weight is concerned and weight control is concerned this is good news, so fiber is our friend.  

High fiber diets are definitely recommended for a variety of general health reasons.  It is typically recommended that most human beings consume 25 to 50 g of fiber per day with an average being 35 g.  People who eat more fiber do not usually suffer from constipation.  They have a lower risk of getting bowel cancer, diabetes, and other types of bowel disease.  Fiber is a natural constituent of fruits, vegetables, beans, grains, lentils, and whole grains, and if you eat plenty of these foods adding fiber to your diet is not necessary.

However, many of us eat processed foods, fast foods which actually contain very little fiber.  In that case, it is important to add fiber to one's diet.  Fiber is calorie-free and it is a natural filler.  Eating more fiber in your diet makes you feel full, less hungry.  

Foods that are high in fiber are more satisfying because they absorb more water, so they become bulkier in our gut.  Wheat fiber as in bran is not a very absorbant fiber compared to some vegetable fibers.  Placed in water it can swell to 10 times its original volume. Glucomannan on the other hand, the fiber from Japanese Konjac plant, however, swells to 100 times its original volume. Glucomannan is given to diabetics in Japan because it helps stabilize blood sugar level by slowly releasing carbohydrates into the blood stream, consequently having a less drastic effect on blood sugar elevation.

There are two primary kinds of fiber in our diet or fiber in our foods:  Soluble fiber and insoluble fiber. Many foods contain both insoluble fibers and soluble fibers. 

Insoluble fiber bulks up fecal content.  It almost acts like broom. It cleanses the intestine, prevents constipation, and produces better stools.

Soluble fibers are different. They actually dissolve in the gut and form an actual gelatinous-like type substance. This kind of fiber slows down the release of glucose in the blood stream, so it is very beneficial for blood glucose management.  It also slows the release of fat into our blood stream which also helps control blood fats. 

Whole grains contain both kinds of fiber and slow down glucose release whereas ground fiber, the type you might find in bread, has very little effect in this way. 

Fruit and vegetable juices that do not have fiber have a very adverse effect on blood sugar level because of a lack of fiber.  It does not slow the digestive process.  Sugars are released into the blood stream very rapidly.  Consequently, elevation of blood sugar level, elevation of blood insulin levels.  The soluble fibers found in beans, lentils, and oats are particularly effective at slowing down the digestion of food and thus blood sugar response.  Insoluble fibers make you feel full immediately after eating while soluble fiber reduces appetite up to 10 hours later and this could be because of the effect on blood glucose in the blood stream.  You do not have the sharp spike and elevation of blood glucose and finally the sudden drop in blood glucose level, leaving you feeling hungry.  There are quite a few different kinds of fibers in both these categories, but it is important to eat unprocessed whole foods to get the most fiber you possibly can.  Of all the fibers, oat fiber is probably the best in terms of controlling blood sugar level which helps in controlling weight.  Some sources of soluble fiber used therapeutically to help with digestion, diabetes, and weight loss are even better.  Psyllium and glucomannan, which I have previously mentioned, are soluble fibers that I have found to be the most effective in controlling blood sugar level, so for diabetics, people who are wishing to lose weight, these are the choices to make.