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.
*Dieters and weight-management advocates may claim benefits for this supplement 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.
Dosage & Side Effects
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.1, 2, 3, 4 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,6, 7, 8 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.10, 11, 12
The most common adverse effects of dietary fiber are minor gastrointestinal symptoms. There have been several reports of allergic reactions to psyllium. In rare cases, obstruction of the large or small intestine has occurred in people consuming wheat bran or bran cereal.
Beans, a good source of soluble fiber, also contain special sugars that are often poorly digested, leading to gas.
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.13
Interactions with Supplements, Foods, & Other Compounds
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, which contains insoluble fiber, reduces the absorption of calcium enough to cause urinary calcium to fall.14 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.15 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.
Soluble fiber is found primarily in fruit, beans, and oats, but it is also available separately as pectin, oat bran, and glucomannan. Two sources of soluble fiber—pectin (found in fruit) and oat bran (a component of oatmeal also available by itself)—have been reported to interact with lovastatin.18 The fiber from these two sources appears to bind the drug in the gastrointestinal tract and reduce absorption of the drug as a consequence. People taking this drug should avoid concentrated intake of soluble fiber, as taking lovastatin with a high soluble-fiber diet leads to reduced drug effectiveness.
Propoxyphene may cause gastrointestinal (GI) upset. Propoxyphene-containing products may be taken with food to reduce or prevent GI upset.19 A common side effect of narcotic analgesics is constipation.20 Increasing dietary fiber (especially vegetables and whole-grain foods) and water intake can ease constipation.
Where to Find It
Whole grains are particularly high in insoluble fiber. Oats, barley, beans, fruit (but not fruit juice), psyllium, chia seed, 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).
The information presented in Aisle7 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 2014.
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