FIBER

 

Studies on Fiber and Diabetes

Physiology and Clinical Effects

Fiber is divided into two general categories—water soluble and water insoluble. Soluble fiber lowers cholesterol.¹ For unknown reasons, diets higher in insoluble fiber appear to correlate better with protection against heart disease², however, soluble fibers can also lower blood sugar levels in people with diabetes, and some researchers find that increasing fiber decreases the body’s need for insulin—a good sign for diabetics.³ Recent research review reveals 50 grams are needed of mostly soluble fiber to really help people with diabetes.  As with heart disease, a clear mechanism to explain how insoluble fiber helps diabetics has not been identified. Nonetheless, diets high in insoluble fiber (from whole grains) associate with protection from adult-onset diabetes and the reduction of post prandial blood glucose.⁵

Insoluble fiber softens stool, which helps move it through the body in less time. For this reason, insoluble fiber is partially effective as a treatment for constipation.⁶ The reduction in “transit time” is thought to also explain why fiber is associated with protection from colon and other gastrointestinal (GI) cancers. However, the true relationship between fiber and colon cancer risk appears more complicated than first believed. For example, wheat bran has been reported in animal research to be significantly more protective than diets not containing wheat bran, but equally high in insoluble fibers.⁷ Fiber may have other anticancer effects unrelated to “transit time” or even to the GI tract.⁸ Some researchers believe that changes in bile acid metabolism in the GI tract may partially explain the special link between wheat bran and prevention of colon cancer,⁹ a protective link sometimes not found when scientists study total fiber or even total grain fiber intake and colon cancer incidence.¹⁰

Fiber also fills the stomach, reducing appetite. In theory, fiber should therefore reduce eating, leading to weight loss. However, studies have show that it is very individual and can show weight loss or not despite decreasing appetite.¹¹

Lignan, a fiber-like substance, has mild antiestrogenic activity. Probably for this reason, high lignan levels in urine (and therefore dietary intake) have been linked to protection from breast cancer in humans.¹²

Food Sources
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 soluble and insoluble fiber. The best source of lignan, by far, is flaxseed (not flaxseed oil, regardless of packaging claims to the contrary).

Deficiency Risk and Symptoms
Most people are fiber deficient. Eating white flour, white rice, and fruit juice (as opposed to whole fruit) all contribute to this problem. Many so-called whole wheat products contain mostly white flour. Read labels and avoid “flour” and “unbleached flour,” both of which are simply white flour. Junk food is also fiber depleted. The diseases listed above (plus colon and breast cancers) are much more likely to occur with low-fiber diets.

Recommended Dosage
Western diets generally provide approximately 10 grams of fiber per day. So-called primitive societies consume 40–60 grams per day. Increasing fiber intake similar to the “primitive” diets is desirable.

Contraindications
While individuals 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 most minerals. To minimize this effect, multimineral supplements should not be taken at the same time as a high-fiber meal.

Bran, an insoluble fiber, reduces the absorption of calcium enough to cause urinary calcium to fall.¹³ As a result of this interaction, kidney stones can sometimes be prevented simply by incorporating one-half ounce of bran per day into the diet.¹⁴ Before supplementing with bran, people should check with a doctor, because some people—even a few with kidney stones—don’t absorb enough calcium. For those people, supplementing with bran might deprive them of much-needed calcium.

Studies on Fiber and Diabetes (click here)

BACK

References:

1. Todd PA, Befield P, Goa KL. Guar gum: a review of its pharmacological properties and use as a dietary adjunct in hypercholesterolemia. Drugs 1990;39:917–28.
2. Jenkins DJA, Kendall CWC, Ransom TPP. Dietary fiber, the evolution of the human diet and coronary heart disease. Nutr Res 1998;18:633–52[review].
3. Anderson JW, Gustafson NS, Bryart CA, Tietyen-Clark J. Dietary fiber and diabetes. J Am Diet Assoc 1987;87:1189–97.
4. Nuttall FW. Dietary fiber in the management of diabetes. Diabetes 1993;42:503–8.
5. Salmeron J, Manson JAE, Stampfer MJ, et al. Dietary fiber, glycemic load, and risk of non-insulin-dependent diabetes mellitus in women. JAMA 1997;277:472–7.
6. Kritchevsky D. Protective role of wheat bran fiber: preclinical data. Am J Med 1999;106(1A):28S–31S.
7. Müller-Lissner SA. Effect of wheat bran on weight of stool and gastrointestinal transit time: a meta analysis. Br Med J 1988;296:615–7.
8. Jacobs DR Jr , Marquart L, Slavin J, Kushi LH. Whole-grain intake and cancer: an expanded review and meta-analysis. Nutr Cancer 1998;30:85–96.
9. Earnest DL, Einspahr JG, Alberts DS. Protective role of wheat bran fiber: data from marker trials. Am J Med 1999;106(1A):32S–7S.
10. Fuchs CS, Giovannucci EL, Colditz GA, et al. Dietary fiber and the risk of colorectal cancer and adenoma in women. N Engl J Med 1999;340:169–76.
11. 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.
12. Adlercreutz H, Fotsis T, Hekkinen R, et al. Excretion of the lignans enterolactone and enterodiol and of equol in omnivorous and vegetarian postmenopausal women and in women with breast cancer. Lancet 1982;ii:1295–9.
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. Brit J Urol 1986;58:592–5.

go back to Herbs page...