Dietary fiber is one of the main components of a healthy human diet. Nutritionists have divided dietary fiber into two general types - the water soluble fiber and the water insoluble fiber. Dietary fibers of which are soluble have an ability to lower the cholesterol level in the body. At the same time, and for reasons that are still a mystery, human diets that contain a higher proportion of the insoluble type of dietary fiber tend to give better protection against the risk of heart disease and related cardiac problems.
In patients affected by lifestyle diseases such as diabetes, the soluble type of dietary fibers can also help lower elevated blood sugar levels, especially if insulin resistance is a serious problem. At the same time, some clinical researchers have discovered that increasing dietary fiber intake lowers the body's requirement for the insulin hormone - this is considered to be a good sign for diabetics, all of whom suffer from insulin resistance to varying degrees. This supposed effect has been questioned by a recent review of research results, which questions the real effectiveness of moderate dietary fiber consumption on insulin resistance. The fact is that, there is a lack of proof about a clear mechanism to show how insoluble fiber helps diabetics, similar to the lack of clear evidence connecting dietary fiber use with reduction in heart disease risk. At the same time, it is known that diets that are high in content of insoluble fiber, especially from whole grains, offer some protection from the late or adult onset diabetes type two.
The consumption of large amounts of insoluble dietary fibers helps in softening the stool, this results in the quick removal of the feces from the body. Dietary fiber is partially effective as a treatment for constipation, for this reason, the insoluble fibers serve as roughage. This shortening of the movement of stool through the tract or the lessening of the "transit time" of stool, is believed to protect a person from the risks of colon and other gastrointestinal cancers. This explanation may not necessarily be so simple, and the actual association between a high fiber diet and the risk of colon cancer seems to be much more complicated than first suggested. This realization has come from the careful analysis of results from different animal based studies, as an example, the consumption of wheat bran was stated to be significantly much more protective for test animals than the consumption of diets that were without wheat bran, but equally high in insoluble fibers from different foods. In addition, dietary fiber could possibly possess other forms of anticancer effects that are not connected to the "transit time" of stool or it may not even be connected to gastrointestinal tract at all but may be affecting some other unknown process. At the same time, certain clinical researchers suggest that the changes in bile acid metabolism occurring in the gastrointestinal tract may be a partial explanation of the special link that exists between the presence of wheat bran and colon cancer prevention. This protection conferred by the wheat bran is not an effect seen with all fiber rich foods; when clinicians studied the total fiber or even total grain fiber intake and colon cancer incidence with respect to other high fiber foods, it was found that, this protective effect was not conferred by most of these other foods.
Dietary fiber reduces appetite because it is very filling due to its bulk. The consumption of dietary fiber should contribute to weight loss, theoretically speaking, as it has bulk. Some researches have, however, found that increasing the dietary fiber intake will have no effect on body weight despite its ability to decreasing appetite over the long term.
The fiber like substance known as lignan, found in many plants possesses a mild anti-estrogenic activity in the body. This is the possible reason for the fact that high lignan levels detected in the urine is linked to a significant protection from breast cancer in humans - high levels of the substance in the urine is simply a reflection of high dietary intake of the substance.
Insoluble dietary fibers are found in high amounts in all types of whole grains. Rich sources of insoluble dietary fiber along with some soluble fibers include oats and barley, beans, as well as psyllium, and some commonly found vegetables and fruits -though fruits juices tend to be poor in fiber content. The flaxseed is the richest source of lignan, but flaxseed oil is not rich in this substance - even though the label on products sold in the market may claim otherwise.
Dietary fiber deficiency seems to affect almost everyone. Modern diets that predominantly consists of processed foods with a lot of white flour, white rice, and fruit juices all contribute to this state of affairs, more so as the consumption of fresh raw vegetables, whole raw fruits and unrefined or whole grains are on the decline everywhere. Processed food seems to dominate the supermarkets and many of the whole wheat products sold in the stores contain mostly white flour. The best way to ensure that one eliminates an excess of white flour from the diet is to read product labels with care and to avoid "flour" and "unbleached flour," both of which are essentially white flour. Dietary fiber is also lacking in the majority of junk foods sold at so many fast food places. Diets that are low in dietary fibers make people susceptible to the diseases that were discussed before, and increase the risk of colon and breast cancers as well.
Dieticians and nutritionist calculate that the average western diet provides about ten grams of dietary fiber per day to a person. This level of consumption is low compared to the so called primitive diet of older societies, where dietary fiber consumption can be about forty to sixty grams of fiber every day per person. It is obvious that most modern diets in the west lack sufficient fiber, therefore, boosting the total fiber intake to the level of the "primitive" diets is not only desirable, but may be the healthiest choice for all concerned.
Although certain people may develop some allergic reactions to certain high fiber foods in the diet - the allergic response is mostly to wheat - the major effect of a high fiber diet is a great improvement in the health of the person. High fiber diets are the cause of health problems in a minuscule percentage of the population - who may already be genetically predisposed to allergic reactions. Examples of a high fiber food include all kinds of beans; this common food is an excellent source of soluble fiber, as well as many kinds of special sugars that are often poorly digested in the body, leading to the production of excess abdominal gas and consequent bloating. This problem can be significantly reduced by consuming certain special enzyme products that are now available in most supermarkets - these products improve the digestion of these sugars and avid the production of excess gas.
Dietary fiber also tends to reduce the rate of absorption of most minerals in the food. The consumption of multi-mineral supplements can overcome this effect to some extent, though such supplements must not be taken along with a high-fiber meal to avoid inhibition of mineral uptake in the stomach.
The insoluble dietary fiber found in bran, tends to reduce the rate of absorption of the essential mineral calcium, to bring about the fall of urinary calcium levels. This creates excess calcium accumulation leading to kidney stones; this eventuality may sometimes be prevented by the simple expedient of incorporating about half an ounce of dietary bran in the diet every day. The advice of a nutritionally oriented doctor is mandatory for all persons who want to use supplements of dietary bran, this precautionary consultation is required as some people may not be absorbing enough calcium in the stomach - this include some individuals already affected by kidney stones. Such individuals may be affected by a deficiency of essential calcium if they supplement with bran over any length of time.