Judith Hallfrisch

Mechanisms of the effects of grains on insulin and glucose responses.

Consumption of a number of grains and grain extracts has been reported to control or improve glucose tolerance and reduce insulin resistance. The inability of the body to maintain normal glucose levels or to require excessive levels of insulin to do so has been called glucose intolerance, impaired glucose tolerance and insulin resistance. These conditions are associated with obesity and may be preliminary steps in the progression to type 2 diabetes mellitus. Although dietary goals recommend the consumption of three servings of whole grains per day, average consumption in the United States is less than one serving per day. There are a number of mechanisms by which grains may improve glucose metabolism and delay or prevent the progression of impaired glucose tolerance to insulin resistance and diabetes. These mechanisms are related to the physical properties and structure of grains. The composition of the grain, including particle size, amount and type of fiber, viscosity, amylose and amylopectin content all affect the metabolism of carbohydrates from grains. Increasing whole grain intake in the population can result in improved glucose metabolism and delay or reduce the risk of developing type 2 diabetes mellitus. Whole grains can provide a substantial contribution to the improvement of the diets of Americans. A number of whole grain foods and grain fiber sources are beneficial in reduction of insulin resistance and improvement in glucose tolerance. Form, amount and method of cooking of these foods as well as the health characteristics, age and gender of the group of subjects studied are all important factors in the effectiveness of the foods in altering these responses. Dietary recommendations of health organizations suggest consumption of three servings a day of whole grain foods; however, Americans generally fall below this standard. Recent research using various grains and grain products effective in improving insulin resistance or lowering glycemic index will be discussed below by possible mechanisms of action.

Effect of beta-glucan level in oat fiber extracts on blood lipids in men and women.

OBJECTIVE An active hypolipidemic component in oats, the soluble fiber beta-glucan, has been concentrated in an oat fiber extract. The oat fiber extract has been used to replace fat in food products. This study was designed to determine if moderate levels of oat fiber extract could be incorporated into a typical diet and whether plasma lipids could be reduced by the amount of beta-glucan added to the diet. METHODS Oat fiber extracts containing low (1% by weight) or high (10% by weight) beta-glucan were fed to 23 mildly hypercholesterolemic subjects (seven men and 16 women). A maintenance diet was fed for 1 week followed by diet containing an oat extract for 5 weeks each in a crossover pattern. Five percent of the energy from fat in the maintenance diet was replaced with the oat extract in the experimental diets. Caloric intake was adjusted to try to maintain each subjects initial weight. Fasting blood was collected several days apart after separate 12 hour fasts the end of each period. Plasma was analyzed for triglycerides, total cholesterol, and lipoprotein cholesterol fractions. RESULTS HDL, HDL2, and VLDL cholesterol, and triglyceride levels after the oat extract diets were not significantly different from those after the maintenance diet. Total and LDL cholesterol levels decreased significantly (p < 0.001) from maintenance levels after both diets containing the oat extracts. Total cholesterol levels after the higher beta-glucan extract diet were significantly lower than those after the low beta-glucan diet. CONCLUSIONS Beneficial reduction of cholesterol was obtained with modest amounts of oat extract incorporated into the diet. A significant dose response due to beta-glucan concentration in the oat extract was observed in total cholesterol levels.

Reduced risk of Alzheimer’s disease with high folate intake: The Baltimore Longitudinal Study of Aging

Study findings have suggested an association between Alzheimers disease (AD) risk and several vitamins and have speculated about their use as preventive agents. Here, we examine whether total intake (intake from diet plus supplements) of antioxidant vitamins (E, C, carotenoids) and B vitamins (folate, B6, and B12) is associated with a reduced risk of AD.

Lipids Significantly Reduced by Diets Containing Barley in Moderately Hypercholesterolemic Men

Objective: To determine whether barley, as the soluble fiber source, would beneficially change cardiovascular risk factors. Soluble fiber from oats has been recognized as beneficial in decreasing blood cholesterol levels. Although barley contains high amounts of soluble fiber, it is not consumed as extensively as oats. Methods: Eighteen moderately hypercholesterolemic men (28–62 y) consumed a controlled equilibration diet (Step 1, 30% fat, 55% carbohydrate, 15% protein, < 300 mg cholesterol) for 2 weeks followed by the diet with about 20% of energy replaced with brown rice/whole wheat, ½ barley & ½ brown rice/whole wheat or barley (< 0.4 g, 3 g and 6 g added soluble fiber/2800 kcal, respectively) for 5 weeks in a Latin square design. Fasting blood was drawn twice weekly. Total cholesterol, HDL cholesterol, and triacylglycerols were measured enzymatically and lipid fractions were measured by nuclear magnetic resonance spectroscopy. Results: Compared with prestudy concentrations, total cholesterol (14%, 17%, and 20%, respectively) and LDL cholesterol (17%, 17%, and 24%, respectively) were significantly lower (p < 0.0001) after the low, medium, and high-soluble fiber diets. Triacylglycerol was 6%, 10%, and 16% lower (p = 0.09) whereas HDL cholesterol (9%, 7%, and 18%) was higher (p < 0.001) after the experimental diets. Total cholesterol and LDL cholesterol after the high-soluble fiber diet were significantly lower than concentrations after the low- or medium-soluble fiber diets. Mean LDL particle number significantly decreased (p < 0.007) and the large LDL cholesterol fraction showed a trend toward lower concentrations (p = 0.06). Conclusion: Increasing soluble fiber through consumption of barley in a healthy diet can reduce cardiovascular risk factors.

Comparison of Hormone and Glucose Responses of Overweight Women to Barley and Oats

Objective: To determine the effect of particle size (flour vs. flakes) on glycemic responses after oats and barley (Prowashonupana cultivar), which contain high amounts of soluble fiber, are consumed by overweight women. Design: Ten women, average age 50 years and body mass index 30, consumed glucose (1 g/kg body weight) and four test meals (1 g carbohydrate/kg body weight; 2/3 of the carbohydrate from oat flour, oatmeal, barley flour, or barley flakes and 1/3 from pudding) in a Latin square design after consuming controlled diets for 2 days. Blood samples were collected at fasting and periodically after each meal. Results: Peak glucose and insulin levels after barley were significantly lower than those after glucose or oats. Glucose areas under the curve (AUCs) after test meals compared with AUCs after glucose were reduced after both oats and barley (29–36% by oats and 59–65% by barley) (p < 0.002). Insulin AUCs after test meals compared with glucose AUCs were significantly reduced only by barley (44–56%) (p < 0.005). Indexes for insulin resistance (HOMA, MFFM, Cederholm) after the oat and barley meals were not different from indexes after the glucose meal. Glucagon and leptin responses did not significantly differ for the carbohydrates tested. Conclusions: Particle size of the oats or barley had little effect on the glycemic responses. Both oat and barley meals reduced glycemic responses; the high soluble fiber content of this barley appeared to be a factor in the greater reduction observed.

Seasonal variation in plasma glucose and hormone levels in adult men and women.

Twenty-nine men and women collected diet records for 1 yr. Fasting blood samples were collected four times during the year so that each season of the year was represented. An oral glucose tolerance test was given in the spring and in the fall. Regardless of season men consumed significantly more kilocalories, carbohydrate, sugar, and starch than did the women. Men consumed more simple sugars in the fall than in the spring. No seasonal effect was observed for calories, total carbohydrate, or starch intake. Fasting glucose and insulin were higher in the fall than in the spring. Summed insulin levels after the oral glucose tolerance were significantly different by age and season. Summed insulin levels were significantly higher in older than younger subjects; men and older subjects had higher levels in the spring than in the fall. Fasting levels of thyroxine, free thyroxine, triiodothyronine, and glucagon varied significantly with the season. A significant sex by season interaction was observed in the thyroid hormones. It appears that seasonal variation as well as diurnal variation should be considered in evaluating hormone levels.

Effect of dietary sucrose and genotype on metabolic parameters of a new strain of genetically obese rat: LA/N-corpulent

Abstract A new strain of genetically obese rat, LA/N-corpulent ( cp ) was studied. Homozygous ( cp/cp ) corpulent and heterozygous ( cp/+ ) and homozygous ( +/+ ) lean young male rats were fed for 4 weeks diets containing 54% carbohydrate as either sucrose or starch. A genotype effect between corpulent and lean rats (corpulent > lean) was observed with food intake, weight gain, total fat pad weight and size, liver weight and size, activities of liver lipogenic enzymes, fasting levels of serum triglyceride, free fatty acid, total cholesterol and insulin, and response levels of serum insulin and glucose. Levels of insulin and triglyceride were 6 to 8 times greater in corpulent than lean rats. The magnitude of metabolic responses in lean rats was similar except for total fat pad weight and size which was greater in cp/+ than +/+ rats. A sucrose effect (sucrose > starch) was observed with weight gain, total fat pad weight and size, liver weight and size, activities of liver lipogenic enzymes, fasting level of serum triglyceride and response levels of serum insulin and glucose. The data demonstrate that corpulent ( cp/cp ) rats have metabolic characteristics similar to type IV hyperlipoproteinemia in humans and that these characteristics are magnified by feeding of sucrose.

Physiological Responses of Men and Women to Barley and Oat Extracts (Nu-trimX). II. Comparison of Glucose and Insulin Responses

ABSTRACT This study was designed to compare the glucose, insulin, and glucagon responses to consumption of high-soluble β-glucan compounds from oats and barley. After an initial medical evaluation that included blood and urine testing, 11 men and 11 women, nondiabetics, 35–57 years, were selected. Subjects consumed a controlled diet for three days. On the third day of five successive periods, subjects consumed 1 g/kg of body weight of carbohydrate as glucose or 0.66 g/kg of body weight pudding (predominantly sucrose) and 0.33 g/kg of body weight as oat bran, barley flour, oat or barley extract (Nu-trimX) in a Latin square design. Order of treatment was randomly assigned. Glycemic responses were calculated using the trapezoid method. Data were analyzed using mixed procedure analysis of variance program. Glucose responses to oats, barley, and both extracts, and areas under the curve were significantly lower than responses to the glucose solution (P < 0.0001). Insulin responses for the barley extract were lo...

The effect of particle size of whole-grain flour on plasma glucose, insulin, glucagon and thyroid-stimulating hormone in humans.

OBJECTIVE Although it is well known that consumption of whole-grain foods with higher fiber content results in beneficial health effects, most Americans usually prefer bread made with white flour. Changes in bread texture and undesirable intestinal responses have been reported as reasons for avoiding consumption of whole-grain foods or high-fiber menus. The purpose of this study was to determine whether consumption of bread made with ultra-fine-ground whole-grain wheat flour retained beneficial effects while reducing undesirable effects. METHODS Twenty-six men and women, 31 to 55 years of age, consumed glucose solutions or bread made with traditional white, conventional whole-grain wheat (WWF), or ultra-fine whole-grain wheat (UFWF) flour (1 g carbohydrate/kg body weight) in a Latin square design after two days of controlled diet. The effect on glycemic response was determined by comparing blood variables, after a tolerance test with white bread, WWF bread, and UFWF bread, with those after a glucose tolerance test. RESULTS Men and women had similar responses to all tolerances except postprandial TSH. Glucose and insulin levels one half hour after the glucose load were significantly higher than after any of the bread tolerances. Glucose, but not insulin, areas under the curve were significantly higher after the glucose load than areas after the three breads. Consumption of UFWF resulted in glucose and insulin responses, as well as areas under the curve, similar to those after consumption of conventional whole-wheat bread. CONCLUSION The particle size of whole grain wheat flour did not substantially affect glycemic responses.

Comparison of seven-day diet record with measured food intake of twenty-four subjects

Abstract A comparison was made between calorie intakes recorded for 7 days by 12 men and 12 women and the calorie levels they consumed during an 18-week controlled dietary study during which body weight was maintained. A large discrepancy was found in the calories consumed during the controlled study and the calories recorded on the 7-day record. The difference between average daily kilocalories women consumed during the study and the number on the diet record was more than 900. Men reported consuming about 500 kcal less per day than they consumed to maintain weight. Men and women both consumed about 43% carbohydrate, 16% protein and 41% fat. P/S ratio was about 0.4 and cholesterol intake was relatively low, averaging 415 mg in men and 335 in women. On the average, men met the RDA for all nutrients reported, but women had low intakes of iron, calcium, and vitamin A. The average number of daily meals consumed was 3.42. The subjects consumed an average of 16% of the calories between midnight and 11:00 AM, 32% between 11:00 AM and 4:00 PM, and 52% between 4:00 PM and midnight. These results indicate that there may be a wide range of calorie intakes at which subjects can maintain body weight. If caloric intakes recorded by the women are accurate and representative, they may have difficulty in obtaining necessary amounts of calcium, vitamin A, and iron without dietary changes or vitamin and mineral supplementation.