You may have heard it time and again, from your doctor, health organizations and the media – eat more fiber. But why is fiber so important these days? Actually fiber has always been an important component of the human diet. The only problem is that the modern diet, which is made up of heavily processed foods, is lower in fiber than that of our ancestors. Furthermore advances in medical science and a better understanding of the importance of good nutrition has highlighted the importance of fiber in disease prevention and management.
About Dietary Fiber
Dietary fiber is known by many names but the most common is roughage or bulk. It is the portion of certain foods that cannot be digested in the human body. Fiber remains in the gut and is eventually expelled with the stool. So why is it so important if the body cannot digest and absorb this food component?
It is exactly the fact that it remains in the gut that fiber is so important in health care. Fiber is able to act in several ways on the foods and drinks that we consume and aid in bowel function. It therefore plays an important role in reducing the impact of the unhealthy modern diet which is major contributing factor for several diseases that we see today.
Types Of Fiber In Food
There are broadly two types of fiber – soluble and insolube fiber.
- Soluble fiber is able to dissolve in water. Since the gut is filled with water during the process of digestion and absorption, the soluble fiber that may be eaten as a solid then dissolves within the gut.
- Insolube fiber is unable to dissolve in water. It may be broken down into smaller portions during mechanical digestion but remains undissolved in the gut. It can absorb water and bulk up in size.
Food usually has a combination of soluble and insoluble fiber. Some foods have more soluble fiber while others may have more insoluble fiber. Although fiber cannot be digested in the human body, it can be fermented by bacteria that naturally resides in the gut. The US Food and Drug Administration (FDA) recommends a daily intake of between 20 to 30 grams of fiber. However, studies have shown that most Americans do not eat this much of fiber and in fact eat less that half of the recommended daily intake.
Fiber And Cholesterol
Although both types of fiber have health benefits, it has been found that soluble fiber plays a significant role in reducing blood cholesterol levels and specifically LDL cholesterol (“bad cholesterol”). It works by reducing the reabsorption of bile from the gut – a normal physiological process. Therefore more bile is passed out in the stool. Bile is made up of cholesterol and through reabsorption, some of the cholesterol is “recycled”.
But when bile reabsorption is reduced then the liver has to make more bile. This means that more cholesterol has to be taken out of the bloodstream to make bile, more of which is then lost in the feces. Just 5 to 10 gram of fiber per day can reduce your cholesterol levels by as much as 5%.
Fiber And Obesity
There are multiple benefits of fiber for weight management. Firstly insoluble fiber adds bulk to food, especially when it absorbs water in the stomach. It expands and gives makes you feel full faster. This means that you are more likely to eat less food. Fiber has no calories and cannot be absorbed so it does not contribute to weight gain.
Secondly, insoluble fiber alters the time period for the absorption of nutrients from the gut. It prevents spikes in the blood glucose levels that may occur with eating foods laden in sugar and refined carbohydrates. Normally these foods are rapidly absorbed, raises the blood glucose levels and insulin is secreted to lower the blood glucose. One of the consequences is that some of this extra glucose is stored as fat. Fiber reduces this effect.
Fiber And Heart Health
Cardiovascular health is dependent on a multitude of factors like non-modifiable risk factors such as a strong family of heart disease. Two of the major modifiable risk factors are high blood cholesterol levels and obesity. The benefits of fiber in reducing blood cholesterol and assisting with weight management has been discussed above. Therefore fiber indirectly has benefits in cardiovascular health.
Reputable organizations like he American College of Cardiology Foundation have done studies over several years to investigate the benefits of fiber in maintaining a healthy heart. The findings of these studies have conclusively verified that maintaining close to the recommended daily intake of fiber reduces the risk of cardiovascular disease.
Fiber And Bowel Health
Fiber is probably best known for its benefits in maintaining healthy bowels. It has several effects that are beneficial to the entire gut and especially the bowels. One of the most important benefits of fiber is that it assists with improving bowel habit and easier bowel movements. By absorbing water and remaining in the bowels, fiber makes stool soft.
It also bulks up the bowel contents. This helps with the quicker movement of digested food, undigested material and wastes. Ultimately fiber can help prevent and even treat constipation. Good bowel habit also helps to prevent or minimize hemorrhoids (piles) and reduces the risk of diverticula (pouches in the colon) or diverticulitis (inflammation of these pouches).
Fiber And Diabetes
Fiber should be an important part of the dietary management of diabetes mellitus (sugar diabetes). It is known that all fiber can assist in controlling the blood glucose levels to some degree. Soluble fiber in particular may be helpful by slowing down the absorption of nutrients and subsequent elevation of blood glucose levels after a meal. This means that less insulin will be required to control blood levels.
In this way fiber can help to alter the glycemic index (GI) of foods. It essentially lowers the glycemic index of high GI foods by a moderate degree. This does not mean that you can eat anything you wish if you are a diabetic. Instead a fiber should be a part of every meal to further improve glucose tolerance beyond the characteristics of the optimal foods for a diabetic.
Fiber And Cancer
A high fiber diet has often been touted as a preventative measure for colon cancer, especially when a person is also on a low fat diet. However, the research supporting the benefits of fiber in reducing colon cancer risk has been inconclusive. Recent studies have shown that fiber does not offer the protection against colon cancer as is often thought. However, a high fiber diet would not be harmful overall and should be maintained.
The research supporting the benefits of fiber in cancer prevention for malignant tumors elsewhere in the body is equally inconclusive. But there may be some indirect effects. For example, natural high fiber food sources like fresh fruits and vegetables may have certain phytochemicals that are beneficial to overall health. Similarly, high fiber diet may have a positive role to play in weight loss which also reduces the cancer risk since obese people have a greater cancer risk.
Article reviewed by Dr. Greg. Last updated on June 14, 2013