We all know that fiber is good for us, yet the subject is never a part of any polite conversation. All too often fiber is still being thought of as a laxative and yet, fiber offers so much more than just an excellent laxative. Its health benefits go way beyond digestive health.
Fiber is a remarkable nutrient that has wide ranging physiological and health benefits including: heart health, cholesterol control, glycemic control, insulin response and sensitivity, gut health, satiety, immune enhancement and as a particularly strong preventative of colon cancer. Indeed, fiber could possibly be one of the most important arsenals in every household to ward off a host of diseases. In fact, the clinical evidence on fiber is more robust than many other nutritional intervention molecules such as vitamins, minerals and many herbs.
So how did fiber become such an important part of our diets?
Denis Burkett was a surgeon from Northern Ireland who, due to an unfortunate incident involving soccer, lost an eye. His injury cost him his job as a surgeon and he was only able to find work as a nurse as no one wanted to be operated on by a one-eyed surgeon! At the start of World War II, he enlisted as a surgeon and served with distinction. After the war again he could not find any work as a surgeon and instead he went to Africa as a missionary doctor. In Uganda, where he was posted, he first discovered a new kind of cancer caused by a virus which was later named after him, Burkett’s lymphoma. Later, he observed the local population was largely free of any cancers of the colon. He attributed this to the fact that the locals were strict vegetarians and consumed very high quantities of fiber, found in vegetables such as cassava, barley and millet. He published a paper in the renowned medical journal The Lancet, and Burkett’s findings were well received all over the world. Fiber became recognized as an important nutrient that doctors and nutritionists began to advocate.
The Institute of Medicine (IOM) recommends that a daily intake of fiber should be 38g for males and 25g for female, the latter requiring more during pregnancy and nursing. However, the average North American adult consumes around half that figure despite the heavy promotion of the health benefits by the government. Over 90% of N American adults view digestive health as a top priority, yet less than half think that they need more fiber in their diets. Clearly greater education on the role of fiber is required for consumer awareness.
What is fiber?
Dietary fiber is the indigestible portion of the plant which usually requires much more chewing, hence the synonymous word “roughage”. Fiber is abundant in various fruits and vegetables and is commonly found in roots, stems and nuts. Coconut and mangoes are great examples of fibrous fruits and nuts.
Fiber constitutes a wide range of plant compounds that are all based on the polysaccharide chain backbone. Polysaccharides are essential complex sugars.
Fibers range from cellulose, the main component of the vegetable kingdom and the chief constituent of leaves, stems and bark of trees to pectin found in apples and grapefruit to beta glucan derived from yeast.
Fiber is a collective term to describe a large and diverse variety of plant constituents that are resistant to breakdown by gastrointestinal enzymes in the small intestines, but undergo fermentation in the large intestines. Dietary fiber is classified as water soluble or water in-soluble, though plants usually contain some combination of the two.
Water insoluble fibers are chiefly derived from cellulose and are abundant in vegetables and cereal grains like wheat and corn. Water-insoluble fibers easily absorb water and help to regulate bowel movement by increasing bulk, softening stools and quickening the transient time of passage through the intestinal tract.
Soluble fibers are generally gel forming, highly viscous and include pectins, mucilage and various gums like guar and xanthan. Dried beans, oats, and barley are major sources of this type of fiber. The soluble fibers are carried to the large intestines where they are broken down by the gut bacteria to release various beneficial components.
Recently, the Japanese company Taiyo has taken the large molecules of guar gum and broken them down to much smaller polysaccharide units that become completely soluble in water and other beverages within two to three minutes leaving an odourless, taste-free and clear solution. This product is called Solu Fiber, it has distinct advantages as one of the drawbacks of taking fiber is that it doesn’t dissolve and often has a distinctive taste. Moreover, the complete solubility of Solu Fiber makes the product very user friendly.
I have mentioned that fiber is one of the most beneficial nutrients to take for enhancing one’s health, but what exactly are the benefits?
Helps reduces Glycemic Index (GI) and Insulin response of foods.
Most foods have a GI (charts listing GI of foods are now available from various websites) which refers to the amount and rate of release of glucose from the food once it is consumed. The higher the GI of a particular food, the greater the amount of glucose and consequently the greater the amount of insulin is released by the pancreas to compensate for the increase in glucose. High GI foods are associated with poor health as the body struggles to keep producing insulin to keep pace with high glucose in the blood. Solu Fiber reduces or blunts the GI of various foods.
While the exact mechanism isn’t known, the available evidence suggests that Solu Fiber may interfere with fat and/or bile acid metabolism. Bile salts help solubilize fats (much like the detergents we use to remove the greasiness off the plates) so they can be reabsorbed by the body. Solu Fiber binds with bile salts in the intestines and is then excreted in the feces. Since bile salts are derived from cholesterol, excess removal of bile salts means more bile salts are produced at the expense of cholesterol in the liver. This has a net cholesterol reducing effect.
Finally, some research indicates that the dissolved fiber forms a layer in the intestines which acts as a physical barrier, thereby preventing re-absorption of cholesterol and bile salts. This in turn, promotes weight loss.
Solu-Fiber helps produce short chain fatty acids (SCFA)
Fiber is not digested in the small intestines, but once in the colon, it is broken down by the specific bacteria residing there. Various metabolites are produced, like the SCFA’s e.g. butyrate as well as other compounds. These SCFA’s are useful as energy sources for various tissue cells. Specifically, butyrate is the primary energy source for the colon cells. In addition SCFA’s regulate the pH thus making the environment inhospitable for various pathogens. Finally, there is evidence to suggest that SCFA’s help reduce cholesterol.
Promoting weight loss
Fiber provides little or no calories, but it does give one the feeling of fullness or satiety unlike many processed foods which are energy dense (full of calories) yet provide little or no feeling of satiety. Some studies show that fiber significantly reduces body fat in animals and humans while others report no weight loss effect. Women consuming at least one serving of whole grain had a significantly lower mean body mass index (BMI) and waist circumference than women not taking the whole grain.
Research seems to indicate that obese subjects have a different gut microbe composition than lean subjects, and changes towards the “lean microbes” can be observed in obese subjects that lose weight.
Elegant experiments show that when the gut microbes from obese mice is transplanted into germ-free mice these mice become obese as well! In other words, the composition of the gut microbes is very important and determines whether we are fat or thin but more importantly the composition can be changed. Dietary fiber has been shown to change the gut microbe composition that favours the “lean microbiota”.
Fiber also enhances mineral absorption of calcium, magnesium, zinc and so on. This effect is particularly true for pre-teens as well as postmenopausal women.
The breakdown product of fiber which occurs via fermentation in the large intestines generates many metabolites or bi-products. The metabolites provide food and nourishment for the friendly bacteria which colonize there. This is called the pre-biotic effect. Support and well-being for these bacteria is critical as these bacteria have an important role to play in various biological pathways from immune stimulation, to breakdown of nutrients to vitamin generation to preventing the colonizing of pathogenic or unfriendly bacteria.
Besides SCFA, other breakdown components or metabolites stimulate the immune system. Fiber is known to activate our immune system.
Improves digestive health
Besides alleviating constipation, a high fiber diet may prevent stress induced diarrhea by preventing the release of various hormones produced by the body which normally quicken the passage in the intestines which results in diarrhea.
Fiber and Inflammation
Recent studies show significant reduction in inflammatory markers (one common method of monitoring inflammation) in subjects consuming high fiber intake. Reduction of inflammatory markers especially c-reactive protein (CRP) has been frequently reported. One of the mechanisms might be the generation of butyrate that is particularly anti inflammatory.
Dietary Fiber has consistently been shown to be an important nutrient from a health perspective with multitude of mechanisms of action. With the availability of novel fibers like Solu Fiber, it is convenient and easy to increase ones intake of fiber unlike the old fashioned fiber products.
How do you make sure to include enough fiber in your diet? Share with us in the comments below!