Daniel J. Scholfield

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.

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.

FEMALE RATS ARE PROTECTED AGAINST THE FRUCTOSE INDUCED MORTALITY OF COPPER DEFICIENCY

Abstract Experiments were conducted in copper deficient male and female rats fed diets containing fructose or starch in order to determine whether the same type of interaction between copper status and dietary carbohydrate found in male rats also occurs in the female rat. Mortality occurred only in the male rats fed the fructose diet deficient in copper with 40% of the animals dying during the 8 week study. Only anemia, hypercholesterolemia, increased BUN, heart hypertrophy and reduced body weight were observed in these animals which could be related to their mortality. Despite the increased mortality, plasma ceruloplasmin, erythrocyte SOD and hepatic copper concentrations were reduced to a similar extent in all rats regardless of the sex of the animals or of the type of dietary carbohdrate fed. The results of the present study indicate that although direct measurements of copper status of female rats fed fructose diet deficient in copper are similar to their male counterpart, they are apparently protected from the lethal consequences of the deficiency.

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.

Development of copper deficiency in rats fed fructose or starch: Weekly measurements of copper indices in blood

Abstract Copper deficiency was induced in weanling rats fed diets whose sole source of carbohydrates was starch or fructose for 7 weeks. Conventional parameters of copper status, plasma copper concentrations, ceruloplasmin activity, and erythrocyte superoxide dismutase (SOD) activity-were longitudinally monitored weekly to follow the development of the deficiency and to correlate these indices with the degree of severity of the deficiency. Although 30% of the rats fed a copper-deficient fructose diet died and no deaths occurred in rats fed the copper-deficient starch diet, plasma copper, ceruloplasmin, and SOD activities were reduced to a similar extent in all rats fed copper-deficient diets regardless of the type of dietary carbohydrate. Thus, none of the indices used accurately reflected the greater degree of deficiency or mortality in rats fed the fructose diet deficient in copper. The results of the present study underscore the need for more sensitive tests or alternative parameters to assess copper status in living animals.

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.

Food Amylose Content Affects Postprandial Glucose and Insulin Responses

ABSTRACT Beneficial reduction in glycemic response has been observed after consumption of some high-amylose foods. This study examined the effect of varying the moisture content and the particle size of the starch in a test food. Twelve men and 12 women consumed corn chips or corn muffins made with starch or starch plus cornmeal from standard corn (30% amylose, 70% amylopectin) or high amylose (70%) corn. Half of the subjects were hyperinsulinemic based on a prestudy glucose challenge. No gender differences were observed. The hyperinsulinemic subjects had significantly higher insulin and glucose responses and area under the curve as compared with the normal responders. Average glucose, insulin and glucagon were usually lower after muffins compared with chips or foods containing cornmeal. Insulin and glucose responses, but not glucagon, were significantly lower after the consumption of foods made with high-amylose compared with standard corn starch and in control versus hyperinsulinemic subjects. Average p...

Diets Containing Soluble Oat Extracts Reduce Urinary Malondialdehyde in Moderately Hypercholesterolemic Men and Women

Soluble oat extracts have been used successfully in a number of diet studies to lower plasma blood lipids. One of the mechanisms proposed for this reduction in lipids is the production of short-chain fatty acids in the large intestine, which, in turn, may inhibit low-density lipoprotein cholesterol synthesis, thereby limiting oxidation. Urinary excretion of malondialdehyde (MDA) is proportional to endogenous lipid peroxidation. The purpose of this report is to examine the effects of consuming oat extracts with low (1%) or high (10%) levels of soluble β-glucans on lipid peroxidation as measured by urinary malondialdehyde excretion. Twenty-four subjects with moderately elevated cholesterol levels (6.0 mmol/L) were selected for the study. A 1-week equilibration period was followed by two 5-week experimental periods during which defined diets contained the 1% or 10% oat extracts in a crossover design. Seventy-two-hr urine samples (3 × 24-hr) were collected at the end of each period. Urinary levels of MDA excreted were 10–18% of dietary MDA consumed. Consumption of either of the oat extracts resulted in highly significant reductions in urinary excretion of malondialdehyde (P < 0.0001). These data would support the hypothesis that oat extracts inhibit endogenous lipid peroxidation by reduction of MDA (a marker for fatty acid oxidation); however, because no significant differences were found in MDA excretion after subjects consumed the two levels of β-glucans, this is apparently not the responsible component. Further examination of this mechanism in the control of lipid metabolism is warranted.

The effects of natural dietary fiber from fruit and vegetables with oxalate from spinach on plasma minerals, lipids and other metabolites in men

Abstract Diets high in fiber and oxalate may result in decreased mineral bioavailability. However, increased fiber intake can reduce risk factors for some diseases. Twelve men were fed diets containing 25g or 5g of neutral detergent fiber with 450 mg/day of oxalic acid for six weeks each in a crossover design to determine whether plasma minerals and other metabolites would be affected. High dietary oxalate levels were fed throughout the study. The fiber sources were fruit and vegetables or their juices and spinach was the source of oxalate. Five minerals and cholesterol, triglycerides, uric acid, glucose and urea nitrogen (BUN) were measured in fasting plasma and correlated with fecal oxalate, mineral intake and apparent mineral balance. Fiber level had no effect on the plasma constituents. Plasma inorganic phosphorus (P 1 ) decreased (p=0.002), while BUN, calcium and copper increased (p i changes which occurred may have been related to ingestion of high levels of oxalate for eighty-four days.