The effects of an oral contraceptive on plasma growth hormone and glucose tolerance in two strains of rats.

Effects of an oral contraceptive on plasma growth hormone and glucose tolerance were studied in two strains of rats, Sprague-Dawley, a normal strain, and BHE, a carbohydrate-sensitive strain. Ethynyl estradiol and norgestrel, combined in a dose representative of the clinical preparation of Ovral were given for 21 days. Plasma growth hormone was measured following sodium pentobarbital stimulation. In both strains fasting blood glucose levels were unchanged following oral contraceptive therapy, however, a strain difference in response to a glucose load was found. With contraceptive steroid treatment, Sprague-Dawley rats developed an impaired tolerance to glucose during the latter part of the glucose tolerance test. BHE control animals had an abnormal response to a glucose load which improved with oral contraceptive therapy. No significant correlation between growth hormone changes and changes in glucose tolerance during contraceptive steroid treatment were observed. Both strains of rats receiving oral contraceptives gained less weight than their controls, however, the difference was statistically significant only in the Sprague-Dawley strain.

PIP: The effects of Ovral (norgestrel plus ethinyl estradiol) on plasma growth hormone (GH) levels and glucose tolerance were investigated in Sprague-Dawley and a carbohydrate-sensitive strain (BHE) of rats. Sodium pentobarbitol was used to stimulate GH production. Fasting blood glucose levels were not altered by treatment with Ovral in either strain. However, under a glucose load, Sprague-Dawley rats developed an impaired tolerance during the latter part of the glucose tolerance test, while treatment with the oral contraceptive improved an impaired response to glucose load in BHE animals. A good correlation between changes in GH and glucose tolerance during treatment could not be established. Sprague-Dawley rats had a significant (p less than .01) decrease in the rate of body weight increase compared with controls.

Plasma pyridoxal phosphate concentrations of men fed different levels of vitamin B-6.

The vitamin B-6 status of 12 white, 3 black, and 7 men of other races was evaluated utilizing plasma pyridoxal phosphate concentrations after the males had been on controlled diets for 8 wk. The diets contained averages of 1.22-1.67 mg/d vitamin B-6 as calculated from food composition tables. The actual mean vitamin B-6 content of these diets as analyzed with Saccharomyces uvarum was 0.75-0.98 mg/d; the mean daily protein intakes were 80.8-84.5 g. All subjects had plasma pyridoxal phosphate concentrations (67.6-125.8 nmol/L) well within the normal range; the values of the different race and dietary groups were similar. Vitamin B-6 requirements were satisfied by the consumption of diets analyzed to contain means of 0.75-0.98 mg/d of the vitamin as demonstrated by plasma pyridoxal phosphate levels indicative of adequate status. Dietary vitamin B-6 intakes should be determined by actual analyses when requirements are being determined.

Mineral retention in young men consuming soy-fiber-augmented liquid-formula diets.

The effect of a nutritionally complete liquid-formula diet without soy polysaccharide or with the fiber source at 20, 30, or 40 g/d on mineral retention in young men was examined. Addition of 20 g soy polysaccharide to the liquid formula significantly (p less than 0.05) improved the retentions of copper, iron, zinc, and magnesium over the diet without added fiber. The highest level of soy polysaccharide (40 g/d) resulted in significantly (p less than 0.05) lower Cu, Zn, Fe, and Mg retentions than did the 20-g diet and the 30-g diet had an intermediate effect. Except for slightly negative Cu (-0.1 +/- 0.4 mg) and Fe (-0.6 +/- 3.7 mg) retentions on the 40-g diet, retentions of all minerals remained positive throughout this study. The liquid-formula diet supplemented with 40 g soy polysaccharide could have a deleterious effect on mineral retentions in persons consuming the diet as their sole nutritional source.

Plasma lipid and lipoprotein cholesterol concentrations in adult males consuming normal and high cholesterol diets under controlled conditions.

Twenty-three young adult males were fed diets containing either 400 or 1400 mg of cholesterol per day under controlled conditions for 4 wk. There were minimal differences between the two diets in total protein, carbohydrate, fat, and the P/S fatty acid ratio. In both diets 400 mg of cholesterol was supplied from nonegg food sources; the additional 1000 mg of cholesterol was from four whole eggs. Blood samples were collected after a 12- to 14-h fast at the beginning of the study, weekly throughout the experimental period, and 1 wk after completion of the study. Plasma total cholesterol and triglycerides and high-density, low-density, and very low-density lipoprotein cholesterol levels were measured. No significant differences in plasma total cholesterol, triglycerides, and lipoprotein cholesterol levels were observed between groups at any time. However, plasma cholesterol and cholesterol content of individual lipoproteins varied considerably among the individual subjects fed the high cholesterol diet. The importance of changes in the properties and metabolic activity of individual lipoproteins induced by dietary cholesterol with or without gross changes in the cholesterol levels remains to be determined.

Effects of short-term aerobic conditioning and high cholesterol feeding on plasma total and lipoprotein cholesterol levels in sedentary young men.

The plasma total cholesterol (TC) and lipoprotein cholesterol concentrations of sedentary young men (n = 23) were determined during 4 wk of controlled feeding and 6 wk of supervised aerobic conditioning. Subjects were assigned to dietary treatments of 400 mg cholesterol per day (M) or 1400 mg cholesterol per day (H); both diets had a P/S ratio of about 0.6. Dietary groups M and H were subdivided into exercise (MX and HX) and sedentary (MS and HS) groups. Compared to the sedentary groups, MX and HX exhibited significant (p less than 0.01) improvements in cardiorespiratory fitness. After 2 and 4 wk of high cholesterol feeding, group HS exhibited significant (p less than 0.05) elevations in TC (+30 +/- 7 and +32 +/- 9 mg/dl) with nonsignificant increases in very low-density lipoprotein cholesterol and low-density lipoprotein cholesterol. Group HX exhibited consistent weekly increases in high-density lipoprotein cholesterol (HDL-C) (from 46 +/- 3 mg/dl, the base level, to 53 +/- 4 mg/dl at wk 4) with aerobic conditioning. By combining exercise and sedentary group data at each level of dietary cholesterol it was shown that TC and HDL-C levels significantly (p less than 0.05) increased by the 4th wk of high cholesterol feeding. The TC/HDL-C ratio significantly (p less than 0.05) increased for the sedentary subjects as compared to all the exercising subjects by wk 4 of controlled feeding.

Effect of coarse wheat bran fiber and exercise on plasma lipids and lipoproteins in moderately overweight men.

The effects of the American Association of Cereal Chemists coarse wheat bran fiber and exercise were evaluated in 20 males, aged 24 to 35 yr, and at least 10% above ideal weight. Thirteen of the subjects participated in a 4 mile walk-jog run program 3 times weekly. In a cross-over design with diets switched midway through the experiment, both the exercising and sedentary groups consumed isocaloric amounts of either white bread or white bread containing wheat bran (0.5 g/kg body weight). Plasma total and lipoprotein cholesterol and triglycerides, body weights, and percentage body fats were determined at 0, 6, and 12 wk. No consistent effects were observed as a result of the wheat bran feeding on any of the parameters measured. Exercise training tended to decrease body weights and percentage body fats, and was associated with significantly increased (p less than 0.05) plasma high-density lipoprotein cholesterol levels and high-density lipoprotein cholesterol to low-density lipoprotein cholesterol ratios. After a rise in triglycerides at wk 6, a significant decline (p less than 0.05) back to base-line values was observed at wk 12 for the exercised subjects.

Exercise capacity and nitrogen loss during a high or low carbohydrate diet.

Twelve obese women completed a maximal and an endurance exercise test (70% peak VO2) during a weight maintenance week. For the next 4 wk, the women consumed either a high (71%) carbohydrate (HC) or a low (33%) carbohydrate (LC), isonitrogenous very-low-calorie diet (VLCD) of 2,219 kJ (530 kcal).d-1. A supervised exercise session at 60% peak VO2 took place 3 times.wk-1 for 30 to 45 min. Peak VO2 and exercise endurance tests were repeated during the fourth week of the VLCD. One week of a 4,186 kJ (1000 kcal) diet followed the VLCD. The average weekly weight loss was 1.7 +/- 0.1 kg for the HC group and 2.0 +/- 0.2 kg for the LC group. Urinary nitrogen loss was greater for the LC group early in the VLCD but not different than HC over the entire experimental period. Serum cholesterol and high-density lipoprotein-cholesterol decreased in both groups but the ratio of these lipids improved over the treatment. Serum beta-hydroxybutyrate and uric acid increased significantly more for the LC than the HC group. Although absolute peak VO2 decreased, VO2 relative to body weight was maintained. Time to exhaustion improved by 36% for both groups in the endurance exercise tests. The endurance exercise R ratio was significantly more depressed by the LC than the HC treatment. In summary, both supervised treatments were effective in causing substantial weight reduction and improved blood lipid profiles in healthy young women but caused a net loss of body protein. Neither treatment compromised ability to participate in a thrice weekly exercise program. Although peak aerobic capacity did not increase, aerobic endurance at a fixed sub-maximal exercise load was improved.

Concentration of plasma cholesterol in beef cows and calves, milk production and calf gain.

Milk yield of 59 beef cows that calved in late September through November was measured monthly in early and late lactation and biweekly during midlactation. Milk yield was estimated by milking with a machine after over-night separation of cows from calves. Concentration of plasma cholesterol of cows and calves was measured when calves averaged 44, 93, 136, and 178 d of age (SD = 17 d). Cholesterol of calves also was measured 2 wk after weaning, when they averaged 220 +/- 2.3 d of age. Cholesterol of calves was highest at second and third samplings and dropped after weaning. The estimated intake of milkfat by calves, and to a lesser extent their intake of milk, was related positively to their plasma cholesterol as they approached weaning age. The relationship was not strong enough, however, for differences among calves in concentration of plasma cholesterol to identify accurately differences in milk yield of their dams. Within breed group, age of cow, and stage of lactation, the regression coefficients of milk yield on plasma cholesterol of cows were close to zero. The concentrations of plasma cholesterol in both cows and calves were highly repeatable, with the exception of samples that were collected when calves averaged 44 d of age. Although plasma cholesterol of calves was related positively to milk yield and milkfat yield in late lactation, the former trait was not an accurate indicator of the two latter traits.

Diet, hormonal, and metabolic factors affecting bone mineral density in adolescent amenorrheic and eumenorrheic female runners.

Seven adolescent female runners with secondary amenorrhea and six adolescent eumenorrheic female runners received dietary supplements of 1200 mg calcium carbonate and 400 IU vitamin D/d for 12 months. Bone mineral density (BMD) of the axial skeleton was measured by dual photon densitometry at the beginning and end of the 12 month period. Plasma estradiol and ionized calcium concentration were also determined. Bone mineral density decreased in two of the amenorrheic subjects, with the lowest estradiol values concurrent with the severest training regimen and highest calcium intake. There was a significant decrease in plasma estradiol concentration in the amenorrheic runners (p less than 0.05). Plasma ionized calcium and estradiol explained 99% of the variation in BMD (r2 = 0.999). A significant inverse relationship between plasma estradiol and miles run/week was observed (r2 = -0.748). Adolescent female runners who train extensively and have low plasma estradiol levels may be adversely affecting BMD despite supplemental calcium and vitamin D intake.

Plasma total and lipoprotein cholesterol, liver cholesterol and fecal cholesterol excretion in hamsters fed fiber diets.

The effect of dietary fibers on plasma lipids, liver cholesterol and fecal cholesterol excretion was investigated in hamsters. Male 9- to 11-wk-old Golden-Syrian hamsters (n = 155) were fed a purified hypercholesterolemic diet (0.1% cholesterol, 10% fat) for 5 wk to elevate plasma lipid concentrations. Sixteen animals with elevated plasma total cholesterol were randomly assigned to each treatment group: control, oat bran, guar gum, cellulose, xylan and terminal groups. After 4 wk of fiber diet consumption, the plasma total cholesterol concentrations were significantly decreased in the oat bran, guar gum and xylan groups (16, 12 and 15%, respectively) (P < 0.05). Plasma HDL cholesterol concentration was significantly decreased only in the guar gum group (12%) (P < 0.05). The combined plasma VLDL+LDL cholesterol concentrations were significantly lowered by the oat bran, xylan and cellulose diets (38, 34 and 40%, respectively) (P < 0.05). After 4 wk of control diet consumption, the liver cholesterol concentration quadrupled to 10.6 mumol cholesterol/g liver (P < 0.05). After 4 wk of consumption of the treatment diets, liver cholesterol was further increased (P < 0.05) only in the cellulose group, to 14.5 mumol cholesterol/g liver. The total fecal cholesterol excretion was the highest (P < 0.05) in the oat bran group. In the present study, oat bran, guar gum and xylan were effective hypocholesterolemic agents in hamsters.

Plasma B6 vitamer and 4-pyridoxic acid concentrations of men fed controlled diets.

A rapid and sensitive procedure is described for the analysis of all the B6 vitamers and 4-pyridoxic acid in human plasma utilizing reversed-phase high-performance liquid chromatography with ultraviolet and fluorometric detection. Pyridoxal phosphate values obtained by radiometric and chromatographic, ultraviolet and fluorometric, assays were highly correlated as were pyridoxine phosphate values determined using both detectors. Plasma B6 vitamer and 4-pyridoxic acid concentrations of 22 men fed diets containing 0.75-0.98 mg of vitamin B6 daily for eight weeks were in the range of reported values; pyridoxal phosphate was their predominant plasma B6 vitamer. This methodology should be useful in the assessment of vitamin B6 requirements.

Nutrition knowledge, opinions, and practices of coaches and athletic trainers at a division 1 university.

The purpose of this investigation was to assess nutrition knowledge, opinions, and practices of coaches and trainers at a Division I university. Participants (n = 53) completed questionnaires regarding nutrition knowledge, opinions, and practices. Descriptive statistics and analysis of variance were used to analyze data. Overall, participants responded correctly to 67% of nutrition knowledge questions. Participants who coached/trained female athletes tended to score better than respondents who coached/trained male athletes. Strength and conditioning coaches and participants with greater than 15 years of experience scored higher than other participants. Nutrition opinions/practices responses revealed that nutritional supplements were provided for all but 6% of participants' athletes. Participants rated body weight as more important than body composition to athletes' performances. Over 30% of participants perceived at least one case of disordered eating within the past year. Some participants (53%) felt that athletes may consume more nutritious meals on team-sponsored trips if given larger food allowances. Thirty percent of participants reported dietitians were available to them; the same percentage reported utilizing dietitians. Coaches and trainers are knowledgeable about some appropriate nutritional recommendations, but registered dietitians or qualified sports nutrition professionals may complement the nutrition-related education and counseling of athletes (23).

Effect of dietary fat and cholesterol on plasma lipids and lipoprotein fractions in normolipidemic men.

In a controlled feeding situation, male subjects were assigned to one of four treatment groups: low fat (31% of total kcal)/low cholesterol (193 mg/d) (LFLC), low fat/usual cholesterol (504 mg/d) (LFUC), usual fat (46% of total kcal)/low cholesterol (UFLC) and usual fat/usual cholesterol (UFUC) intake. For the first 2 wk of the 10-wk study all subjects consumed the UFUC diet. Subjects consumed experimental diets during wk 3-7 and resumed their customary intake during wk 8-10. Plasma total, high-density-lipoprotein (HDL), low-density-lipoprotein and very-low-density-lipoprotein cholesterol and triglycerides were determined weekly. A significant effect (P less than 0.05) of dietary fat on plasma total and HDL cholesterol was observed between the end of wk 2 and 7. Low fat intake resulted in 17 +/- 2 mg/dL lower total cholesterol and 10 +/- 1 mg/dL lower HDL cholesterol than the usual fat intake. Plasma lipids were not affected either by dietary cholesterol or by any interaction of dietary fat with cholesterol.

Carcass nitrogen as a predictor of protein requirement for mature female rats.

The minimal level of dietary protein required for maintenance of nitrogen equilibrium was investigated using Sprague-Dawley rats, 12 months of age. Rats were fed casein, supplemented with methionine, at levels ranging from 0.84 to 5.18% of the diet for 4, 8 or 12 weeks and were compared to a control group fed a similar diet containing 9.90% protein or to a baseline group fed a stock diet. The effect of dietary protein levels on total serum protein and on liver and carcass composition was assessed. Protein requirement levels with 95% confidence intervals were predicted by linear regression. Dietary protein levels of 2.14% or lower were not adequate to maintain body weight and serum protein levels, and animals fed these diets had elevated levels of liver lipid. Protein nutriture of rats fed 3.20% protein was generally intermediate between those fed 2.14% or less and those fed 3.62% or greater. Compared to carcass nitrogen, carcass water was not as reliable a parameter for determination of protein requirements. Using the baseline group for comparison and carcass nitrogen as the dependent variable, a dietary protein requirement was predicted for these animals of 3.91--4.19% with confidence intervals of 3.50--4.56% and 3.13--5.48%, respectively. This level is comparable to the maintenance protein requirement of 4% indicated by the National Research Council for adult rats.

Oat products and lipid lowering. A meta-analysis.

OBJECTIVES: To test the a priori hypothesis that consumption of oats will lower the blood total cholesterol level and to assess modifiers and confounders of this association. DATA SOURCES: A computerized literature (MEDLINE) search and the Quaker Oats Co identified published and unpublished trials as of March 1991. Raw data were requested for all trials. STUDY SELECTION: Trials were included in summary effect size estimates if they were randomized and controlled, if a formal assessment of diet and body weight changes occurred, and, if raw data were not received, if there was enough information in the published report to perform calculations. DATA SYNTHESIS: Twenty trials were identified. Using the methods of DerSimonian and Laird, a summary effect size for change in blood total cholesterol level of -0.13 mmol/L (-5.9 mg/dL) (95% confidence interval [CI], -0.19 to -0.017 mmol/L [-8.4 to -3.3 mg/dL]) was calculated for the 10 trials meeting the inclusion criteria. The summary effect size for trials using wheat control groups was -0.11 mmol/L (-4.4 mg/dL) (95% CI, -0.21 to -0.01 mmol/L [-8.3 to -0.38 mg/dL]). Calculation of Keys scores demonstrated that substituting carbohydrates for dietary fats and cholesterol did not account for the majority of blood cholesterol reduction. Larger reductions were seen in trials in which subjects had initially higher blood cholesterol levels (greater than or equal to 5.9 mmol/L [greater than or equal to 229 mg/dL]), particularly when a dose of 3 g or more of soluble fiber was employed. CONCLUSION: This analysis supports the hypothesis that incorporating oat products into the diet causes a modest reduction in blood cholesterol level.