Dietary fiber comes from the thick cell wall of plants. It is an indigestible complex
carbohydrate. Fiber is divided into two general categories-water soluble and water
insoluble.
Where is it found?
Whole grains are particularly high in
insoluble fiber. Oats, barley,
beans, fruit (but not fruit juice),
psyllium, and some vegetables contain
significant amounts of both forms of fiber and are the best sources of soluble fiber. The best
source of lignan, by far, is flaxseed (not
flaxseed oil, regardless of packaging claims to the contrary).
Why do dieters use it?*
Some dieters say that fiber
helps suppress their appetites.
What do the advocates say?*
Unlike laxatives, fiber can truly help regulate bowel patterns. If you choose to take a
fiber supplement, be sure you don’t inadvertently purchase a laxative supplement
instead. The labels on both types of supplements may say something like “regulates bowel
patterns.” While the featured ingredient of fiber supplements will likely be an
ingredient such as psyllium, the featured ingredient of laxatives tend to be herbal-based.
Such supplements are designed only for short-term constipation.
While there is weak evidence that fiber may promote a feeling of fullness, it seems to be
necessary to use it in conjunction with a diet and exercise program in order to be effective
for contributing to weight loss.
The best way to get fiber is from food. However, if you don’t include enough
fiber-rich food in your diet and choose to use a fiber supplement instead, choose a product
that has different types of fiber in it—both soluble and insoluble. When taking a fiber
supplement, be sure to stay well hydrated.
How much is usually taken by dieters?
Fiber supplements are one way to add fiber to a weight-loss diet. Several trials have shown
that supplementation with fiber from a variety of sources accelerated weight loss in people
who were following a low-calorie diet.1234
Other researchers found, however, that fiber supplements had no effect on body weight, even
though it resulted in a reduction in food intake.5 Supplementation with 3 to 4
grams per day of a bulking agent called glucomannan, with or without a low-calorie diet, has
promoted weight loss in overweight adults,678 while 2 to 3
grams per day was effective in a group of obese adolescents in another controlled
trial.9 However, guar gum, another type of fiber supplement, has not been effective
in controlled studies for weight loss or weight maintenance.1011
12
Are there any side effects or interactions?
While people can be allergic to certain
high-fiber foods (most commonly wheat), high-fiber diets are more likely to improve
health than cause any health problems. Beans,
a good source of soluble fiber, also contain special sugars that are often poorly digested,
leading to gas. Special enzyme products are
now available in supermarkets to reduce this problem by improving digestion of these
sugars.
Fiber reduces the absorption of many minerals. However, high-fiber diets also tend to be
high in minerals, so the consumption of a high-fiber diet does not appear to impair mineral
status. However, logic suggests that calcium,
magnesium and multimineral supplements should not be taken at the
same time as a fiber supplement.
Bran, an insoluble fiber, reduces the absorption of calcium enough to cause urinary calcium
to fall.13 In one study, supplementation with 10 grams of rice bran twice a day
reduced the recurrence rate of kidney stones
by nearly 90% in recurrent stone formers.14 However, it is not known whether other
types of bran would have the same effect. Before supplementing with bran, people should check
with a doctor, because some people—even a few with kidney stones—do not absorb
enough calcium. For those people, supplementing with bran might deprive them of much-needed
calcium.
People with scleroderma (systemic sclerosis) should consult a doctor before taking fiber
supplements or eating high-fiber diets. Although a gradual introduction of fiber in the diet
may improve bowel symptoms in some cases, there have been several reports of people with
scleroderma developing severe constipation and
even bowel obstruction requiring hospitalization after fiber supplementation.15
Are there any drug
interactions?
Certain medicines may interact with fiber. Refer to drug interactions for a list of those medicines.
*Dieters and weight-management advocates may claim benefits for fiber
based on their personal or professional experience. These are individual opinions and
testimonials that may or may not be supported by controlled clinical studies or published
scientific articles on fiber. For more complete and detailed information, including references
and safety information, see Fiber as a nutritional
supplement.
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. Marquette CJ Jr. Effects of bulk producing tablets on hunger intensity
in dieting patients. Obes Bariatr Med 1976;5:84–8.
2. Rossner S, von Zweigbergk D, Ohlin A, Ryttig K. Weight reduction with
dietary fibre supplements. Acta Med Scand 1987;222:83–8.
3. Ryttig KR, Tellnes G, Haegh L, et al. A dietary fibre supplement and
weight maintenance after weight reduction: a randomized, double-blind, placebo-controlled
long-term trial. Int J Obes 1989;13:165–71.
4. Solum TT, Ryttig KR, Solum E, Larsen S. The influence of a high-fibre
diet on body weight, serum lipids and blood pressure in slightly overweight persons. A
randomized, double-blind, placebo-controlled investigation with diet and fibre tablets
(DumoVital). Int J Obes 1987;11 Suppl 1:67–71.
5. Hylander B, Rössner S. Effects of dietary fiber intake before
meals on weight loss and hunger in a weight-reducing club. Acta Med Scand
1983;213:217–20.
6. Biancardi G, Palmiero L, Ghirardi PE. Glucomannan in the treatment of
overweight patients with osteoarthritis. Curr Ther Res 1989;46:908–12.
7. Vita PM, Restelli A, Caspani P, Klinger R. Chronic use of glucomannan
in the dietary treatment of severe obesity. Minerva Med 1992;83:135–9 [in Italian].
8. Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese
patients: a clinical study. Int J Obes 1984;8:289–93.
9. Livieri C, Novazi F, Lorini R. The use of highly purified
glucomannan-based fibers in childhood obesity. Pediatr Med Chir 1992;14:195–8
[in Italian].
10. Kovacs EM, Westerterp-Plantenga MS, Saris WH, et al. The effect of
addition of modified guar gum to a low-energy semisolid meal on appetite and body weight loss.
Int J Obes Relat Metab Disord 2001;25:307–15.
11. Beattie VA, Edwards CA, Hosker JP, et al. Does adding fibre to a low
energy, high carbohydrate, low fat diet confer any benefit to the management of newly
diagnosed overweight type II diabetics? Br Med J (Clin Res Ed)
1988;296:1147–9.
12. Pasman WJ, Westerterp-Plantenga MS, Muls E, et al. The effectiveness
of long-term fibre supplementation on weight maintenance in weight-reduced women. Int J
Obes Relat Metab Disord 1997;21:548–55.
13. Shah PJR. Unprocessed bran and its effect on urinary calcium
excretion in idiopathic hypercalciuria. Br Med J 1980;281:426.
14. Ebisuno S, Morimoto S, Yoshida T, et al. Rice-bran treatment for
calcium stone formers with idiopathic hypercalciuria. Br J Urol
1986;58:592–5.
15. Gough A, Sheeran T, Bacon P, Emery P. Dietary advice in systemic
sclerosis: the dangers of a high fibre diet. Ann Rheum Dis 1998;57:641–2.
The information presented in Healthnotes is for informational purposes
only. It is based on scientific studies (human, animal, or in vitro), clinical
experience, or traditional usage as cited in each article. The results reported may not
necessarily occur in all individuals. For many of the conditions discussed, treatment with
prescription or over the counter medication is also available. Consult your doctor,
practitioner, and/or pharmacist for any health problem and before using any supplements or
before making any changes in prescribed medications. Information expires June 2009.
