|
|
WHAT ABOUT DIETARY FIBER?Articles - Dr. Bernstein Shares His Insights Richard K. Bernstein, M.D., F.A.C.E., F.A.C.N., C.W.S. shares his insight on fiber from his new book. Click here to read WHAT ABOUT DIETARY FIBER?Diabetes Solution Revised and Updated 2007 A P P E N D I X A “Fiber” is a general term that has come to refer to the undigestible portion of many vegetables and fruits. Some vegetable fibers, such as guar and pectin, are soluble in water. Another type of fiber, which some of us call roughage, is not water soluble. Both types appear to affect the movement of food through the gut (soluble fiber slows processing in the upper digestive tract, while insoluble fiber speeds digestion farther down). Certain insoluble fiber products, such as psyllium, have long been used as laxatives. Consumption of large amounts of dietary fiber is usually unpleasant, because both types can cause abdominal discomfort, diarrhea, and flatulence. Sources of insoluble fiber include most salad vegetables. Soluble fiber is found in many beans, such as garbanzos, and in certain fruits, such as apples. I first learned of attempts at using fiber as an adjunct to the treatment
of diabetes about thirty years ago.At that time, Dr.David Jenkins, in England, reported that guar gum, when added to bread, could reduce the
maximum postprandial blood sugar rise from an entire meal by 36 percent
in diabetic subjects. This was interesting for several reasons. First of
all, the discovery occurred at a time when few new approaches to controlling
blood sugar were appearing in the medical literature. Second, I
missed the high-carbohydrate foods I had given up, and hoped I might
possibly reinstate some. I managed to track down a supplier of powdered
guar gum, and placed a considerable amount into a folded slice of bread.
I knew how much a slice of bread would affect my blood sugar, and so as Dr. Jenkins also discovered, however, that the chronic use of guar gum resulted in a reduction of serum cholesterol levels. This is probably related to the considerable recirculation of cholesterol through the gut. The liver secretes cholesterol into bile, which is released into the upper intestine. This cholesterol is later absorbed lower in the intestines, and eventually reappears in the blood. Guar binds the cholesterol in the intestines, so that rather than being absorbed, it appears in the stool. In the light of these very interesting results, other researchers studied
the effect of foods (usually beans) containing other soluble forms of
fiber.When beans were substituted for faster-acting forms of carbohydrate,
postprandial blood sugars in diabetics increased more slowly,
and the peaks were even slightly reduced. Serum cholesterol levels were
also reduced by about 15 percent. But subsequent studies, reported in
1990, have uncovered flaws in the original reports, casting serious
doubt upon any direct effect of these foods upon serum lipids. In any
event, postprandial blood sugars of diabetics were never normalized by Many popular articles and books have appeared advocating “highfiber” diets for everyone—not just diabetics. Somehow, “fiber” came to mean all fiber, not just soluble fiber, even though the only viable studies had utilized such products as guar gum and beans. In my experience, reduction of dietary carbohydrate is far more effective in preventing blood sugar increases after meals. The lower blood sugars, in turn, bring about improved lipid profiles. It is true, however, that low-carbohydrate vegetables are usually composed mostly of insoluble fiber and therefore contain far less digestible carbohydrate than starchy vegetables. Thus if we compare fiber to starch, there is great value in “high fiber.” Another food to join the high-fiber trend is oat bran. This has gotten
a lot of play in the popular press. A patient of mine started substituting
oat bran muffins for protein in her diet. Before she started, her
HgbA1C (see Chapter 2) was within the normal range and her ratio of
total cholesterol to HDL was very low (meaning her cardiac risk ratio
was low). After three months on oat bran, her HgbA1C became elevated
and her cholesterol-to-HDL ratio nearly doubled. I tried one of
her tiny oat bran muffins after first injecting 3 units of fast-acting insulin
(as much as I use for an entire meal). After 3 hours, my blood Beware of commercial “high-fiber” products that promise cholesterol reduction. If they contain carbohydrate, they must at least be counted in your meal plan and will probably render little or no improvement in your lipid profile. Fiber, like carbohydrate, is not essential for a healthy life. Just look at the Eskimos and other hunting populations that survive almost exclusively on protein and fat, and don’t develop cardiac or circulatory diseases.* * As the first edition of this book was going to press, a report appeared entitled “Dietary Fiber, Glycemic Load, and Risk of Non-Insulin-Dependent Diabetes in Women” (Jnl Amer Med Assoc 1997; 277:472–477). This study of 65,173 nurses and former nurses found a strong association between diets high in starch, flour, and sweet foods and the development of type 2 diabetes. Furthermore, consumption of minimally refined grain (such as bran without flour) lowered this risk. The combination of high glycemic foods and low intake of unrefined insoluble fiber was associated with a 2.5-fold higher incidence of diabetes. If you remember our discussion of beta cell burnout (pages 39–42), this should come as no surprise. ================================
|
 |
|
WHAT ABOUT DIETARY FIBER?
Get Adobe Acrobat Now