What is Fiber?
Fiber is a substance found in plants. Dietary fiber, which is the type of fiber you can eat, is found in fruits, vegetables, and grains. It is an important part of a healthy diet.
Dietary fiber adds bulk to your diet. Because it makes you feel full faster, it can help with weight control. Fiber aids digestion and helps prevent constipation. It is sometimes used for the treatment of diverticulosis, diabetes, and heart disease.
There are two forms of fiber: soluble and insoluble.
Soluble fiber attracts water and turns to gel during digestion. This slows digestion. Soluble fiber is found in oat bran, barley, nuts, seeds, beans, lentils, peas, and some fruits and vegetables. Research has shown that soluble fiber lowers cholesterol, which can help prevent heart disease.
Insoluble fiber is found in foods such as wheat bran, vegetables, and whole grains. It appears to speed the passage of foods through the stomach and intestines and adds bulk to the stool.
Health Benefits of Fiber Supplements
Cardiovascular Disease – The AI level of 14 g of fiber per 1000 kcals of energy consumed is based on protection against cardiovascular disease (CVD); so the data for this relationship are strong. Epidemiologic studies suggest that adequate fiber intake consistently lowers the risk of CVD and coronary heart disease (CHD), primarily through a reduction in low density lipoprotein (LDL) levels.
Type II Diabetes and Glycemic Control – There are many theories surrounding the relationship between fiber intake and type II diabetes. For example, regularly consuming the recommended amount of fiber has the potential to attenuate glucose absorption rate, prevent weight gain, and increase the load of beneficial nutrients and antioxidants in the diet, all of which may help prevent diabetes.”
Numerous large-scale cohort studies support a strong inverse relationship between dietary fiber consumption and development of type II diabetes. A multi-ethnic cohort followed 75,000 people for 14 years. People who ate more than 15 g of fiber per day had significantly lower diabetes risk. People who ate high amounts of insoluble fiber (more than 17 g/day) or cereal fiber (more than 8 g/day) had less type II diabetes risk than people who had lower intakes while soluble fiber intake was not associated with diabetes risk.
Laxation and Regularity – It is well recognized that fiber is important for normal laxation. This is due primarily to the ability of fiber to increase stool weight. The increased weight is due to the physical presence of the fiber, water held by the fiber, and increased bacterial mass from fermentation. Larger and softer stools increase the ease of defecation and reduce transit time through the intestinal tract, which may help to prevent or relieve constipation. In general, cereal fibers are the most effective at increasing stool weight.
Appetite Control – Multiple mechanisms describe how fiber influences satiation and satiety. Greater satiation may be a product of the increased time required to chew certain fiber-rich foods. Increased time chewing promotes saliva and gastric acid production, which may increase gastric distention. Some soluble/viscous fibers bind water, which also may increase distention. Stomach distension is believed to trigger afferent vagal signals of fullness, which likely contributes to satiation during meals and satiety in the post-meal period.
Body Weight – Prospective cohort studies report that people who consume higher amounts of fiber weigh less than people who consume lesser amounts. One study reported that in a 20-month period, every 1 g increase in total fiber consumed per day, decreased body weight by 0.25 kg.
Immune Function and Inflammation – Some fibers may also play a role in improving immune function via production of SCFAs. In animal studies, addition of SCFAs to parenteral feeding increases T helper cells, macrophages, and neutrophils, and increased cytotoxic activity of natural killer cells. There is also some evidence of increased resistance to illness or infection with fiber intake.
What types of fiber supplements are available?
There are many different types of fiber supplements available and may be in powder, capsule, tablet, or “chew” form. Fiber supplement powders that can be added to beverages are the most common.
The fiber ingredient will be listed on the label of the fiber supplement. Common fiber ingredients used in fiber supplements include:
• Wheat dextrin
• Inulin or Oligofructose (chicory root fiber)
• Hydrolyzed guar gum
How much fiber is recommended?
It is recommended that older women consume about 21g of fiber a day and older men aim for 30g per day. However, fiber intakes of older adults may fall below recommendations. It is often difficult for some older adults to meet their fiber needs through diet alone as they eat less food than younger people. Some older adults may avoid some highfiber foods due to expected problems chewing these foods.
When it is difficult for older adults to meet their recommended fiber intake within their usual diet or when constipation is present, fiber supplementation may be recommended.
Older adults suffering from constipation should consult a doctor or Registered Dietitian (RD) prior to choosing a fiber supplement.
“Eating a large amount of fiber in a short period of time can cause intestinal gas (flatulence), bloating, and abdominal cramps. This problem often goes away once the natural bacteria in the digestive system get used to the increase in fiber. Adding fiber to the diet slowly, instead of all at one time, can help reduce gas or diarrhea.”
“Too much fiber may interfere with the absorption of minerals such as iron, zinc, magnesium, and calcium. In most cases, this is not a cause for too much concern because high-fiber foods tend to be rich in minerals.”
Dietary fiber or roughage is the indigestible portion of food derived from plants. It has two main components:
– Soluble fiber, which dissolves in water, is readily fermented in the colon into gases and physiologically active byproducts, and can be prebiotic and viscous. It delays gastric emptying which in turn can cause an extended feeling of fullness.
– Insoluble fiber, which does not dissolve in water, is metabolically inert and provides bulking, or it can be prebiotic and metabolically ferment in the large intestine. Bulking fibers absorb water as they move through the digestive system, easing defecation.
Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed. Some types of soluble fiber absorb water to become a gelatinous, viscous substance which is fermented by bacteria in the digestive tract. Some types of insoluble fiber have bulking action and are not fermented. Lignin, a major dietary insoluble fiber source, may alter the rate and metabolism of soluble fibers. Other types of insoluble fiber, notably resistant starch, are fully fermented. Some but not all soluble plant fibers block intestinal mucosal adherence and translocation of potentially pathogenic bacteria and may therefore modulate intestinal inflammation, an effect that has been termed contrabiotic.