Introduction:
Recommended dietary fiber intakes are meant for the general
population. There are, however patients who may need individualized
fiber plans, as too much or too little fiber can be detrimental to
their health.
Types of fiber:
1. Nonfermentable or Insoluble: These include lignin, cellulose,
and hemicelluloses. These act to increase fecal bulk and
decrease intestinal transit time.They are found in all plants,
whole grains, wheat, wheat bran, wheat products, rye, rice,
and vegetables.
2. Viscous or Soluble: These include pectins, gums, mucilages, and
some hemicelluloses. They act to delay stomach emptying and
slow glucose absorption, and they can lower blood cholesterol.
They are found in citrus fruits, apples, bananas, oat products,
carrots, barley, beans, and in thickeners added to foods.
3. Functional Fibers: Fibers added to foods to provide health
benefi ts.
4. Prebiotics: A category of functional fibers, which includes a
group of short-chain carbohydrates or oligosaccharides that
are resistant to digestion, but fermented by bacteria in the
colon. They are thought to stimulate the growth or activity of
benefi cial bacteria in the large intestine and therefore promote
the host’s health.[4]
Benefi ts of fiber:
Maintaining bowel regularity:
Thereby decreasing constipation.
Excessive pressure in the large intestine from constipation may lead
to hemorrhoids or diverticula. If diverticula is asymptomatic, as is
the case in 80% of affected people, it is called diverticulosis, if it is
infl amed and painful it is known as diverticulitis. If diverticulitis
occurs, intake of fiber should actually be reduced to limit further
bacterial activity. Once the infl ammation subsides, a high-fiber
diet is resumed to ease stool elimination and reduce the risk of
a future attack.
Weight control:
The bulky nature of high-fiber foods requires more time to chew, satisfi es us and fi lls us up without yielding
many calories.
Treatment of diabetes:
Consuming large amounts of viscous
fibers, such as oat fiber, slows glucose absorption from the small
intestine, and so contributes to better blood glucose regulation,
and decrease in insulin. In fact, adults whose main carbohydrate
sources are low-fiber foods are much more likely to develop diabetes
than those who have high-fiber diets.
Reducing blood cholesterol:
Reducing blood cholesterol and
possibly reducing the risk of cardiovascular disease and gallstones.
This is because a high intake of viscous fiber inhibits absorption of
cholesterol and cholesterol-rich bile acids from the small intestine.
Also, the benefi cial bacteria in the large intestine degrade soluble
fiber and produce certain fatty acids that probably reduce cholesterol
synthesis in the liver. In addition, one of the effects of insulin is
to stimulate cholesterol synthesis in the liver, so the reduction
in insulin may contribute to the ability of viscous fiber to lower
blood cholesterol.
Decreasing incidence of colon cancer:
Many population studies
have shown a link between increased fiber intake and a decrease
in colon cancer development. The health benefi ts to the colon that
arise from a high-fiber diet are partially due to the nutrients that
are commonly present in most high-fiber foods, such as vitamins,
minerals, phytochemicals, and in some cases essential fatty acids.
Thus, it is more advisable to increase fiber intake using fiber-rich
foods, rather than relying on fiber supplements.[1]
How much fiber do we need?
The Adequate Intake of fiber for adults is 25 grams per day for
women and 38 grams per day for men. The goal is to provide at
least 14 grams per 1000 kcal in a diet. After age 50, the Adequate
Intake falls to 21 grams per day and 30 grams per day, for women
and men, respectively.
The Daily Value used for fiber on food and supplement labels is
25 grams for a 2000 kcal diet.[4]
Following a diet which meets the fiber recommendations is possible
and enjoyable if you incorporate plenty of whole-wheat bread,
fruits, vegetables, and beans. However, the fiber recommendations above are for normal healthy
individuals only! Some patients need tailored fiber intakes. According
to their condition, some patients need high fiber diets, while others
actually require low fiber diets.
High-Fiber Diets:
High-fiber diets are those containing 30 grams
or more dietary fiber.They are believed to help prevent constipation,
diverticulosis, hemorrhoids, and colon cancer.They also are helpful
in the treatment of diabetes mellitus and atherosclerosis. It is
currently estimated that most people get only about 11 grams of
dietary fiber each day. A high-fiber diet is often 25 to 35 grams
and should not exceed 50 grams a day. The recommended foods
for this diet include coarse- and whole-grain breads and cereals,
bran, all fruits and vegetables (especially raw), and legumes. Milk,
meats, and fats do not contain fiber. A high fiber diet is nutritionally
adequate.[2]
When implementing a high fiber diet, two precautions must be taken:
1. High-fiber diets must be introduced gradually to prevent the
formation of gas and the discomfort that accompanies it.
2. Eight 8-ounce glasses of water also must be consumed along
with the increased fiber.
Very high fiber diets:
Very high intakes of fiber, for example 60
grams per day, should be followed only under the guidance of
a physician. Increased fl uid intake is extremely important with
these diets.
Problems with High-Fiber Diets:
1. Inadequate fl uid intake can cause severe constipation and may
even contribute to blockages in the intestine, requiring surgery.
2. A high fiber diet may also decrease the availability of nutrients.
Certain components of fiber may bind to essential minerals, keeping
them from being absorbed. For example, Zinc and iron absorption
may be hindered.
3. In children, a very high fiber intake may reduce overall calorie
intake, because fiber can quickly fi ll a child’s small stomach before
food intake meets energy needs.[1]
Fiber-Restricted diets:
Diets of 5 to 10 grams of dietary fiber a
day are intended to reduce the normal work of the intestines by
restricting the amount of dietary fiber and reducing food residue.
Fiber restriction is recommended during acute phases of intestinal
disorders, as ulcerative colitis, when the presence of fiber may
exacerbate intestinal discomfort or cause diarrhea or blockages.
Fiber-restricted diets are used before some surgeries to minimize
fecal volume and after surgeries, especially gastrointestinal surgery,
during transition to a regular diet.
Fiber-restricted diets often eliminate or restrict whole-grain breads
and cereals, nuts and seeds, raw and dried fruits, berries, dried
beans and peas, chunky peanut butter,winter squash, and most raw vegetables.[4,5]
Low-Residue diets:
When even greater reductions in colonic
residue are required, this can be achieved by following a lowresidue
diet, although the terms “low-fiber diet” and “low residue
diet” are often used interchangeably. Low residue diets may be
used in cases of severe diarrhea, diverticulitis, ulcerative colitis,
and intestinal blockage and in preparation for and immediately
after intestinal surgery. In some facilities, these diets consist of
foods that provide no more than 3 grams of fiber a day and that
do not increase fecal residue. A low- residue diet excludes, in
addition to, most fruits and vegetables, foods high in resistant
starch, milk products that contain signifi cant lactose, and foods
that contain fructose or sugar alcohols (such as sorbitol). These
foods contribute to colonic residue because some of their nutrients
may be poorly digested (such as the lactose in milk) or poorly
absorbed,example, sorbitol and fructose.
Some foods that do not actually leave residue in the colon are
considered low-residue foods because they increase stool volume or
provide a laxative effect. Milk and prune juice are examples. Milk
increases stool volume, and prune juice acts as a laxative.[4,3]
Some foods to be allowed in low residue diet plans include eggs,
soup broth, meats, chicken, fi sh and other proteins, carbonated
beverages, tea, coffee, custards,cottage cheese,ice cream, refi ned
carbohydrates as macaroni, pasta, white rice and crackers,cakes
and cookies.
Note that low residue diets should only be followed for limited
periods of time, or else they must be supplemented to avoid
nutritional defi ciencies.
Conclusion:
It is very important that the patient’s condition must be fully
understood, before any dietary fiber recommendations can be
given. Also, complete follow up of the patient is vital to reveal
any possible complications or defi ciencies, and to deal with them
accordingly.
References:
- Nutrition and Diet Therapy, 10th edition, By Ruth A. Roth
- Food and Nutrition by Don Ross, Oxford Book Company, 2010
- Clinical nutrition in practice by Nikolaos Katsilambros. [et al.].
- Contemporary Nutrition, 7th edition, By Gordan M. Wardlaw
and Ann M. Smith
- Understanding Normal and Clinical Nutrition, 8th Edition,
By Sharon Rady Rolfes, et al.
