Dietary fiber: in vitro methods that anticipate nutrition and metabolic activity in humans

Article Abstract:

Dietary fiber plays several complex roles in human nutrition. As a result, it is futile to discuss the sheer quantity of dietary fiber without considering which particular fiber is present, and it is useless to compare different fibers without a knowledge of the various functions of each. Since it is time-consuming and expensive to evaluate many different dietary fibers either in humans or experimental animals, it would be advantageous to devise laboratory methods which might provide insight into the effects which dietary fiber is thought to have within the living body. Researchers have now accomplished this by modeling in the laboratory the four basic functions of dietary fiber. The first two are, in fact, reasonably well understood. Dietary fiber decreases the rate at which glucose can diffuse and be absorbed by the intestines. Dietary fiber also increases the water-holding capacity of the feces, thereby increasing stool weight. However, two other important functions are less easily studied in the laboratory. Dietary fiber binds bile acids and dietary cholesterol; both these processes can have an effect on serum cholesterol. Bile acids are close chemical relatives of cholesterol. They are secreted in the bile, but are brought back into the body through the small intestine. If these bile acids adhere to dietary fiber, however, they may not be returned to the body and may instead be lost in the feces. Similarly, the cholesterol from a meal may not be absorbed if it is bound to fiber. These effects can contribute to the lowering of serum cholesterol. The fourth major function is the interaction of fiber with the fermentation occurring in the cecum. The cecum, a blind pouch at the junction between the small and large intestines, is essentially a bag of bacteria engaging in chemical breakdown of the fiber and other substances. This breakdown affects the function of the fiber during the very last stages of the digestive process. The process was modeled in the laboratory by mixing a bacterial nutrient broth with the dietary fiber and samples of bacteria from a patient's feces. When the laboratory methods were applied to samples of 10 different dietary fibers, the results were similar to, but not identical to, the results observed inside the digestive system. The laboratory methods will probably be useful for the preliminary evaluation of dietary fibers prior to more detailed nutritional studies. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Food, High-fiber diet, High fiber diet

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Psyllium fiber reduces rise in postprandial glucose and insulin concentrations in patients with non-insulin-dependent diabetes

Article Abstract:

Patients with diabetes have trouble controlling the amount of sugar (glucose) in their blood. Several studies have reported that soluble dietary fiber, when taken along with a meal, can reduce the amount of sugar and insulin (a hormone that controls blood sugar) in the blood of patients with non-insulin-dependent diabetes. However, in two other studies soy and psyllium fiber (two types of soluble fiber) did not lower blood levels of sugar and insulin in patients with diabetes. Therefore, a study was performed to determine if eating psyllium fiber along with a standard breakfast or dinner can lower blood sugar and insulin levels in 18 patients with non-insulin-dependent diabetes. The patients were not allowed to eat for 12 hours prior to the beginning of the study. At breakfast, the patients ate a standard meal that contained either psyllium fiber or a placebo. Five hours later, the patients ate a standard lunch without psyllium; and five hours after lunch, the patients ate a standard dinner that contained either psyllium fiber or a placebo. Blood sugar and insulin levels were measured before and after each of the meals. Compared with the placebo, the psyllium fiber reduced blood sugar and insulin levels by 14 percent and 12 percent, respectively, following breakfast. Also, the psyllium fiber reduced blood levels of sugar by 31 percent after lunch, and 20 percent following dinner, compared with the placebo. The same effects were observed in diabetic patients who were taking medication and those who were controlling their diabetes with a modified diet. It is concluded that psyllium fiber can reduce blood sugar and insulin levels following a meal in patients with non-insulin-dependent diabetes. (Consumer Summary produced by Reliance Medical Information, Inc.)

Type 2 diabetes, Psyllium

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Dietary fiber supplementation: effect on exocrine pancreatic secretion in man

Article Abstract:

Animal research has suggested that dietary fiber may influence the functioning of the pancreas. The pancreas is a gland located behind the stomach that secretes various enzymes and hormones involved in digestion and metabolism; pancreatic juice is secreted into the small intestine by way of ducts. The amount of pancreatic enzymes reaching the small intestine was measured in six adult male volunteers who followed a high-fiber diet for four weeks. Subjects ate 20 grams of supplemental dietary fiber per day in the form of biscuits, in addition to their usual diet. The fiber in the biscuits was primarily insoluble, the type found in wheat bran. The contents of the stomach and duodenum (part of the small intestine) were removed by tube and tested for concentration of pancreatic enzymes. Levels of pancreatic lipase, an enzyme involved in fat digestion, were significantly higher on the high-fiber diet, but other pancreatic enzymes were not affected. A high-fiber diet may be helpful in delaying pancreatic insufficiency in patients with chronic pancreatitis (inflammation of the pancreas). But in healthy individuals, an increase in pancreatic lipase is not likely to have any clinical significance because normal lipase secretion is in excess of the amount needed for digestion of fats.

Care and treatment, Research, Enzymes, Pancreas, Pancreatitis, Pancreatic secretions

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