Controlling Blood Sugar to Regulate Body WeightJuly 2007
By Debra Fulghum Bruce, PhD
Those who struggle with obesity often suffer from dangerously elevated glucose (blood sugar) levels.
Beta-glucans (derived from oats and barley) slow the absorption of carbohydrates—enabling one to control blood sugar levels and induce the satiety needed to achieve healthy weight management.
Side benefits of controlling blood glucose include lowering harmful blood fats and C-reactive protein. When blood sugar levels are stabilized, metabolic syndrome and diabetes can be averted.
In this article, we explore how beta-glucans can protect against degenerative disease while offering a decisive advantage for those looking to take control of their blood sugar and their waistline.
Fiber-Deficient Diet Elevates Disease Risk
A number of health problems that plague aging adults—from high cholesterol to diabetes—can often be traced to inadequate levels of dietary fiber.1 Plant-derived fibers play many useful roles in the body, including binding with water to help propel partially digested foods through the intestinal tract. Principal dietary sources of fiber include whole grains, legumes, nuts, fruits, and vegetables.
Americans consume an average of about 14 grams of fiber each day—less than half the amount recommended by the American Diabetes Association for disease prevention and wellness.2 In recent decades, as consumption of processed food has greatly increased, fiber intake has similarly decreased. The result is that most Americans are severely deficient in dietary fiber, and thus at much higher risk of contracting disease. In fact, a diet rich in fiber—particularly from cereal grains—is associated with a 40-50% lower risk of coronary heart disease and heart attack.3
Fiber Modulates Post-Meal Blood Sugar Response
The meager amounts of fiber that characterize the modern Western diet are a potent contributor to aberrant blood sugar metabolism and the growing epidemic of insulin resistance, metabolic syndrome, and type II diabetes.
Currently, about 35 million Americans between the ages of 40 and 74 have impaired fasting glucose, and 16 million have impaired glucose tolerance. Because so many people have both conditions, the total number of adults aged 40 to 74 with pre-diabetes in the United States is estimated to be an astounding 41 million!7
We now know there is a direct link between ingesting carbohydrates and the resultant postprandial (after-meal) blood sugar response.8 After eating a large meal containing ample amounts of quickly absorbed carbohydrates and little soluble fiber, an individual may experience significant postprandial (after-meal) hyperglycemia, or high blood sugar.
How quickly blood sugar rises sometimes depends on the glycemic index of the food consumed. The glycemic index is a numerical system that ranks foods on a scale of 0 to 100, according to how quickly their ingestion increases blood glucose levels relative to pure glucose itself. Although different foods may supply the same amount of carbohydratesper serving, they can have very different glycemic indexes.
For example, highly processed foods such as white bread and doughnuts send blood sugar levels soaring, and have glycemic indexes of approximately 73-76.9 By contrast, naturally fiber-rich foods such as beans and raw pears slowly increase blood glucose and thus have far lower glycemic indexes, of approximately 29-38.9 Harvard studies suggest that the carbohydrate composition of foods plays a large role in their ability to promote or impair one’s health. High-glycemic-index foods that rapidly increase blood sugar contribute to the risk of heart disease and diabetes.10
However, not all fiber is created equal, especially when it comes to favorably influencing the glycemic index of foods. Scientists from the Agricultural Research Service found that barley fiber containing soluble beta-glucan fiber was more effective in regulating peak glucose response than wheat, a whole grain that contains no beta-glucans. They also noted beneficial reductions in glucose and insulin levels when oat-derived beta-glucans were ingested at mealtime.10 Other scientists have found that adding soluble fiber such as oat and barley beta-glucans to the diet helps modulate the after-meal rise in blood sugar, along with the insulin response to a meal containing carbohydrates.11-13
The low glycemic index values of oats or barley, both rich in beta-glucans, may stem from their ability to form a viscous gel with water in the gastrointestinal tract. This thick, gelatinous mixture delays the release of the stomach’s contents into the small intestine for further digestion. This contributes to slower production and release of insulin by the pancreas,14 as well as a slower rate of glucose uptake from the small intestine.15 Thus, the high viscosity of beta-glucans may play a critical role in reducing the more dangerous aspects of the glycemic response to a meal.
Fiber May Help Avert Metabolic Syndrome, Diabetes
Growing evidence suggests that soluble dietary fiber may play an important role in averting the dangers of metabolic syndrome, a precursor to diabetes associated with an elevated risk of cardiovascular disease.16 Metabolic syndrome refers to the constellation of metabolic abnormalities that includes abdominal obesity, high blood pressure, high blood sugar, high triglycerides, and low levels of beneficial high-density lipoprotein (HDL).
A study of the prevalence of metabolic syndrome in the Framingham Offspring Cohort found that it was significantly less common among those who ingested the most whole grains and cereal fiber.17 Given both the high fiber content and a low glycemic index attributed to whole-grain foods, increasing one’s intake of whole grains may reduce the risk of developing metabolic syndrome. Since metabolic syndrome commonly precedes full-blown type II diabetes, dietary intervention with whole-grain fibers may help keep diabetes at bay.
Dietary fibers also benefit those who already have type II diabetes. When diabetic patients consumed a healthy diet that substituted oat beta-glucans for some dietary fat, they exhibited notable improvements in metabolic parameters such as weight, HDL, and long-term blood sugar control.15
Beta-Glucans Lower Cholesterol, Improve Lipids
Many physicians have long advised their cardiac patients to consider adding soluble fiber to their meals in order to reduce cholesterol levels. According to both the Third Report of the Expert Panel on Detection, the Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III) and the American Heart Association,18,19 the gel-forming characteristic of soluble fiber has been shown to improve lipid profiles.20 In one meta-analysis, researchers determined that for every 1-gram increase in soluble dietary fiber, potentially dangerous low-density lipoprotein (LDL) was reduced by 2.2 mg/dL on average.21
In particular, beta-glucan fibers are thought to lower cholesterol by increasing the bulk, volume, and viscosity of the intestinal tract’s contents, thus altering cholesterol and lipoprotein metabolism in the liver. Beta-glucans increase the excretion of bile acids released from the gall bladder. These bile acids are made up of oxidized cholesterol. The liver uses cholesterol to make more bile, which has the net effect of decreasing the amount of harmful LDL circulating in the blood.4 Thus, beta-glucans not only lower cholesterol, but also help to maintain already-normal levels of cholesterol.
In a recent study in Venezuela, investigators set out to determine the effect of bread formulated with 6 grams of beta-glucans (oat-derived soluble fiber) on serum lipids of overweight men with mild to moderate hypercholesterolemia (high cholesterol). After eating a low-fat diet for one week, the men were divided into two groups. One group stayed on the American Heart Association (AHA) Step II diet with whole-wheat bread, while the other group remained on the AHA Step II diet containing high levels of monounsaturated fatty acids plus bread made with 6 grams of beta-glucan. It was suggested that all men exercise 60 minutes each day.22
After eight weeks, both groups of men reduced their body weight significantly. Those who ingested bread containing 6 grams of beta-glucans saw an impressive increase in their levels of beneficial HDL, which remained unchanged in the other group. Non-HDL cholesterol decreased in the beta-glucans group, and the total cholesterol/HDL ratio was reduced. While the diet with whole-wheat bread had no effect on fasting plasma glucose, the beta-glucans diet resulted in a decrease in fasting blood glucose. All of these improved lipid profiles reduced the risk of cardiovascular disease in the beta-glucans group.22