Effects of dietary vitamin E and high supplementation of vitamin C on plasma glucose and cholesterol levels

Weanling male Sprague Dawley rats were fed ad libitum a purified basal diet free of vitamins E and C. In Experiment I (4 weeks), 24 rats were divided into four groups with 2×2 factorial design. They were supplemented with 0 or 45 IU/kg diet of vitamin E, and O or 2.0 g/kg diet of vitamin C. In Experiment II (16 weeks), 36 rats were divided into six groups with 2×3 factorial design. Vitamin E was supplemented at the level of O or 45 IU/kg diet, and vitamin C was supplemented at the level of O, 1.5, or 3.0 g/kg diet, respectively. Plasma glucose level and cholesterol level were determined in both experiments. The plasma levels of glucose and cholesterol were significantly and negatively correlated. Plasma glucose level was significantly increased and plasma cholesterol level significantly decreased by the high supplementation of vitamin C with or without vitamin E in the diet. Vitamin E deficiency decreased plasma glucose level and increased plasma cholesterol level significantly with or without vitamin C supplementation. The groups with adequate level of vitamin E (45 IU/kg diet) and no vitamin C showed moderate plasma glucose and cholesterol levels.     

Effect of soy protein varying in isoflavone content on serum lipids in healthy young men

BACKGROUND: Previous research supports a role for soy protein in reducing serum lipids; however, few studies involved healthy male subjects or focused on soy isoflavones (or did both). OBJECTIVE: The objective was to ascertain the effects of soy protein varying in isoflavone content on serum lipids in healthy young men. DESIGN: Thirty-five males (x +/- SD age: 27.9 +/- 5.7 y) consumed milk protein isolate (MPI), low-isoflavone soy protein isolate (low-iso SPI; 1.64 +/- 0.19 mg aglycone isoflavones/d), and high-isoflavone SPI (high-iso SPI; 61.7 +/- 7.4 mg aglycone isoflavones/d) for 57 d each, separated by 4-wk washout periods, in a randomized crossover design. Blood samples were collected at the beginning and end of each treatment period, and total, LDL, and HDL cholesterol; triacylglycerols; apolipoprotein (apo) B; apo A-I; and C-reactive protein (CRP) were measured in serum. Twenty-four-hour urine samples were collected for 3 consecutive days at the end of each treatment period and analyzed for isoflavones. RESULTS: Urinary isoflavones were significantly greater with consumption of the high-iso SPI than with that of the low-iso SPI or MPI. The differences between the 3 treatments with respect to individual serum lipids were not significant, but the ratios of total to HDL cholesterol, LDL to HDL cholesterol, and apo B to apo A-I were significantly lower with both SPI treatments than with MPI treatment. CONCLUSION: Soy protein, regardless of isoflavone content, modulates serum lipid ratios in a direction beneficial for cardiovascular disease risk in healthy young men.     

健康儿童血清维生素E水平现状分析

目的 了解全国健康儿童血清维生素E水平状况,为合理膳食指导提供依据。 方法 利用反相高效液相色谱荧光检测法测定血清维生素E水平,对《维生素A、E水平与儿童反复呼吸道感染疾病发生、发展的相关性研究》课题组中保健门诊健康体检儿童的临床资料进行分析。 结果 符合入组标准儿童共41 964例,血清维生素E水平(9.12±2.96)mg/L,血清维生素E水平随年龄增加有减低趋势(P<0.001)。维生素E缺乏与不足占21.49%,其中,缺乏者仅为3.36%(1 409/41 964),不足儿童占18.13%(7 609/41 964)。不同年龄段儿童维生素E缺乏及不足比例不同,小于3岁组儿童维生素E缺乏、不足分别为4.1%、13.0%;3岁以上儿童维生素E缺乏、不足分别为2.5%、24.0%(P<0.001)。不同区域儿童血清维生素E水平存在差异,东部、中部儿童血清维生素E水平高于西部和东北部儿童(P<0.001)。 结论 我国婴幼儿维生素E营养状况良好,3岁及以上儿童维生素E缺乏及不足者占1/4,原因尚需进一步研究。     

Effects of dietary cholesterol and fat on serum non-cholesterol sterols according to different apolipoprotein E subgroups among healthy men

The impact of apo E phenotypes on applicability of relative cholesterol synthesis (lathosterol:cholesterol) and absorption (ratios of cholestanol, campesterol and sitosterol to cholesterol) during diets of various cholesterol and fat content is unclear. We examined and compared with each other both relative and absolute synthesis and absorption among twenty-nine men, of whom eight, nine and twelve had apo E phenotypes 2 (2/2, 2/3, 2/4), 3 (3/3) and 4 (3/4, 4/4), respectively. Serum lipids, lipoproteins, sterols and cholesterol metabolism were examined on four subsequent diets: high-cholesterol high-fat (home diet; HD), low-cholesterol low-fat (LCLF), high-cholesterol low-fat (HCLF) and low-cholesterol high-fat (LCHF). LDL-cholesterol (LDL-C) level was about 40 % lower (P < 0.05) in apo E2 than apo E3 and E4 groups irrespective of dietary fat and cholesterol. Serum proportions of phytosterols were determined apo E-dependently on LCLF and HCLF, and those of lathosterol, cholestanol and campesterol were increased in apo E2 and E3 groups (P < 0.05 for each v. HD). Serum proportion of sitosterol reflected almost consistently apo E phenotype (r range+0.308 to+0.383; P range 0.214-0.011). Relative cholesterol synthesis and absorption reflected respective absolute values during each diet in the apo E4 group (r range+0.713 to+0.893; P < 0.05 for each), but only during HD (r+0.594; P = 0.015) in the apo E2+E3 group. The consumption of a high amount of fat did not interfere with cholesterol metabolism or serum levels of LDL-C differently in apo E phenotypes. Surrogate sterol markers of cholesterol metabolism reflected absolute ones (especially in the apo E4 group) and apo E phenotypes despite variable amounts of dietary cholesterol and fat.     

Effects of dietary protein on growth and on plasma and liver vitamin A and E levels in young rats

The effects of dietary protein sources on rat plasma and liver vitamin A and E levels were studied in male weanling rats fed purified 20% protein diets for 28 days. Diets contained adequate amounts of all vitamins and minerals. The food efficiency values expressed as percentages of ANRC casein ranged from 85 to 99 with the exception of liver powder, which was 45. The liver vitamin A levels ranged from 131 to 320 μg/g. The liver vitamin A levels were higher for soy isolate, soy flour, blue-green algae (BGA) and liver powder than for ANRC casein (P<0.05). The high-lactose whey group had the lowest vitamin A levels; liver powder had the highest. The liver vitamin E levels ranged from 42 to 96 μg/g. The liver vitamin E levels with all protein sources, except wheat-milk and milk-egg-BGA, were lower than for ANRC casein (P<0.05). Liver vitamin E levels for textured soy protein, low-lactose whey and BGA were approximately 47% lower than for soy isolate, high-lactose whey and milk-egg-BGA, respectively. ANRC casein had the highest plasma vitamin A and E levels (P<0.05). Milk-egg-BGA, liver powder and BGA caused the greatest reductions in plasma vitamin E, 48, 59 and 88%, respectively. The results suggest that food processing and/or protein matrices may possibly affect liver and plasma vitamin A and E levels.     

Effects of a soy milk supplement on plasma cholesterol levels and oxidative DNA damage in men--a pilot study.

BACKGROUND: Phytoestrogens are a major component of Asian diets and may be protective against certain hormone-dependent cancers (breast and prostate) and coronary heart disease. They may also have antioxidant function in scavenging potentially harmful free radicals and thus decreasing oxidative attack on DNA. AIMS OF THE STUDY: A pilot study to determine the effects of a phytoestrogen supplement, in the form of soy milk, on plasma LDL and HDL cholesterol levels and DNA damage in men. METHODS: Ten healthy men participated in the study and were assigned to one of three groups consuming 1 litre of either soy milk, rice dream (vegetable protein control) or semi-skimmed cow's milk (animal protein control) each day for 4 weeks. RESULTS: The soy supplement caused significant increases in plasma genistein and daidzein concentrations despite considerable inter-individual variation (P < 0.001). Supplementation with soy resulted in a decrease in oxidative damage to DNA bases detected using the comet assay compared with controls (P < 0.05). However, there was no significant effect of the soy supplement on plasma cholesterol or triglyceride levels in comparison with control groups. CONCLUSIONS: A 4 week soy milk supplementation in healthy volunteers does not alter serum cholesterol levels but can have a protective effect against oxidative DNA damage in lymphocytes.     

牛奶和豆浆对男性青年血浆钙磷及激素影响

目的探讨分别饮用牛奶和豆浆对健康男性大学生血浆中钙、磷、胰岛素、葡萄糖、雌二醇和睾酮水平的影响。方法将36名大学生随机分为牛奶组、豆浆组,矿泉水组,每组12人,连续3周每天饮用指定样品1000mL,测定干预前后血浆中相关生化指标的变化。结果干预前3组间指标无明显差异;干预后牛奶组和豆浆组血钙水平分别上升了0.19和0.20mmol/L(P<0.005);豆浆组血磷水平(1.34±0.17)mmol/L明显高于矿泉水组(1.17±0.20)mmol/L(P<0.05);牛奶组血浆雌二醇水平(37.92±10.98)pg/mL明显高于矿泉水组(30.42±9.22)pg/mL(P<0.05);3组之间血浆胰岛素和血糖无明显差异。结论饮用牛奶后血钙水平在正常范围内有所上升;饮用豆浆后血钙、血磷均在正常范围内有所上升;饮用牛奶提高了雌二醇水平。     

Effects of feeding 4 levels of soy protein for 3 and 6 wk on blood lipids and apolipoproteins in moderately hypercholesterolemic men

BACKGROUND: Replacing animal protein with soy protein has been shown to reduce total and LDL-cholesterol concentrations in humans. However, the minimum amount of soy protein required for significant reduction of blood lipids is not known. OBJECTIVE: We evaluated the amount of soy protein needed to reduce blood lipids in moderately hypercholesterolemic men. DESIGN: Eighty-one men with moderate hypercholesterolemia (total cholesterol concentration between 5.70 and 7.70 mmol/L) were studied. After a 3-wk lead-in on a Step I diet, total cholesterol was measured and subjects were randomly divided into 5 groups. For 6 wk, each group received 50 g protein/d, which included isolated soy protein (ISP) and casein, respectively, in the following amounts: 50:0, 40:10, 30:20, 20:30, and 0:50 (control group) g. Blood was collected at baseline and weeks 3 and 6 of the intervention. RESULTS: At week 6, significant reductions (P < 0.05) from baseline compared with the control group were found for non-HDL and total cholesterol and apolipoprotein (apo) B for all ISP groups (except total cholesterol with 40 g ISP). At week 3, significant reductions (P < 0.05) were found in apo B for the groups that consumed >/=30 g ISP and in non-HDL cholesterol for the groups that consumed >/=40 g ISP. HDL-cholesterol, apo A-I, lipoprotein(a), and triacylglycerol concentrations were not significantly affected by dietary treatment. CONCLUSION: Our findings show that consuming as little as 20 g soy protein/d instead of animal protein for 6 wk reduces concentrations of non-HDL cholesterol and apo B by approximately 2.6% and 2.2%, respectively. 2000;71:-84.     

Effects of soya-bean protein and casein on serum cholesterol levels in rats

1. The effect of the soya-bean protein isolate and casein, both given 200 g/kg diet for 3-4 weeks, on serum cholesterol was compared in male rats. 2. Soya-bean protein exerted a hypocholesteramic effect only in a cholesterol-free low-fat (10 g maize oil/kg) diet, when the lowering action appeared independent of the strain of the rat or the feeding pattern. The results obtained with diets containing cholesterol or higher levels of fats or both showed no definite pattern of response. 3. Although the decrease in serum cholesterol appeared greater in alpha-lipoproteins than in beta-lipoproteins, the proportion of the former to total cholesterol remained almost unchanged. The concentration of serum apo A-I was significantly lower in rats given the vegetable protein. 4. Rats given soya-bean protein excreted significantly more neutral sterols. 5. The serum amino acid pattern did not reflect the difference in dietary protein. Addition of cholesterol to the diets modified the serum aminogarm, the decrease in threonine being most marked in both protein groups. 6. This study shows that the hypocholesteraemic action of soya-bean protein is easily modified by the type of diet.     

Effect of hyperbaric oxygen and vitamin C and E supplementation on biomarkers of oxidative stress in healthy men

The objectives of the present study were to evaluate the effect of normobaric and hyperbaric O2 (HBO) on plasma antioxidants and biomarkers of oxidative stress in plasma and urine and to investigate the effect of a 4-week vitamin C plus E supplementation on HBO-induced oxidative stress. Nineteen healthy men were exposed to HBO (100 % O2; 240 kPa) before and after 4 weeks' supplementation with 500 mg vitamin C plus 165 mg alpha-tocopherol equivalents. Exposure to 21 % O2 at 100 kPa served as intra-individual controls (control). Samples for the analysis of plasma antioxidants and oxidative stress biomarkers were collected before and immediately after each treatment. The present results showed that when compared with 'control', a single exposure to HBO resulted in a decrease of plasma vitamin C (P = 0.027) and an increase of lipid peroxides (P = 0.0008) and urinary 8-oxo-deoxyguanosine (8-oxodG) excretion (P = 0.006). Oxidative stress was not prevented by a 4-week supplementation with vitamins C and E. HBO-induced changes in plasma parameters correlated with basal antioxidant levels. The increase of urinary 8-oxodG after HBO plus supplementation correlated negatively with vitamin E intake (P = 0.023). We concluded that in healthy men HBO caused oxidative stress, which could not be prevented by dietary vitamin C plus E supplementation. The present data support the idea that HBO is a suitable model for oxidative stress in healthy volunteers.     

Effect of dietary protein on vitamin E levels in erythrocytes and tissues of rats

The effect of dietary protein level on the transfer of alpha-tocopherol in blood to tissues including RBC was studied using rats. The first experiment comprised a 10% casein (low protein), 20% casein (normal) and 20% SPI (normal soybean protein) diet groups supplemented with 71.5 mg of alpha-Toc/kg diet. In Exp. 2 the relationship of the tissue alpha-Toc level and protein level in diets, as shown by recovery from vitamin E-deficient status after the administration of alpha-Toc for 3 days, was checked by adjusting the protein level in diets to 10%, 20% and 40% casein. In Exp. 1 alpha-Toc in RBC decreased significantly in the 10% casein and 20% SPI groups compared to the 20% casein group. Moreover, alpha-Toc in kidney, lung and muscle decreased significantly in the 10% casein and 20% SPI groups. alpha-Toc in liver in the 20% SPI group decreased significantly compared to the 20% casein group. In Exp. 2 similar results were observed (Table 4), but alpha-Toc in RBC showed only a tendency to decrease with the low protein diet. In Exp. 1 free cholesterol in RBC increased significantly in the 10% casein group compared with the other two groups.     

Effects of a progestogen and a sequential type oral contraceptive on plasma vitamin A, vitamin E, cholesterol and triglycerides.

Fasting blood samples were taken from 13 college students who had never been on oral contraceptives in two menstrual cycles. During the first cycle, the control cycle, each girl donated three blood samples; the first sample was given between days 1 and 5, the second sample between days 13 and 17, and the third sample between days 22 and 26 of the menstrual cycle. In the second menstrual cycle, the experimental cycle, nine girls were given Micronor, a progestogen type oral contraceptive and four girls were given Ortho-Novum SQ, a sequential type oral contraceptive. Four blood samples were obtained from each of the subjects: the first three samples were obtained in the three periods corresponding to those in the control cycle, and the fourth was taken 2 days after the subjects had stopped taking the oral contraceptive. Results showed that estrogen significantly raised plasma vitamin A and triglycerides. The progestogen, at low concentration, had little or no effect on these two lipid materials. At a higher concentration the progestogen enhanced the effect of the estrogen on plasma vitamin A and triglycerides. These effects were extended to at least 2 days after subjects had ceased taking the oral contraceptive. Plasma vitamin E levels in the subjects given Ortho-Novum SQ, were consistently but not statistically higher in the experimental cycle than in the control cycle. The correlation coefficient between vitamin E and triglycerides was statistically significant while those between the vitamin A and vitamin E and between vitamin A and triglycerides were not. Cholesterol was not affected by either Micronor or Ortho-Novum SQ.     

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.     

Effects of omega 3 fatty acids and vitamin E on hormones involved in carbohydrate and lipid metabolism in men.

Forty healthy men were fed diets providing 40% of energy from fat and a minimum of 25 mg vitamin E for 28 wk. During the first 10 wk diets were supplemented with placebo, 15 g mixed fat/d. During the second 10 wk placebo was replaced by 15 g fish-oil concentrate/d. During the last 8 wk 200 mg vitamin E/d was added to fish oil. Compared with placebo, fish-oil feeding significantly increased plasma glucose and decreased triacylglycerol, insulin, glucagon, growth hormone, and somatomedin C. The changes in plasma cholesterol, cortisol, and dehydroepiandrosterone sulphate (DHEA-S) were not significant. Fish oil plus vitamin E further decreased insulin, growth hormone, and DHEA-S and reversed the effect of fish-oil on somatomedin C. The changes in glucose, glucagon, growth hormone, and cortisol were not significant. Thus, changes in plasma glucose and lipids caused by dietary fish oil alone and with fish oil plus vitamin E appear to be due to alterations in hormones involved in carbohydrate and lipid metabolism.     

Oat bran lowers plasma cholesterol levels in mildly hypercholesterolemic men.

The effects of oat bran and wheat bran on plasma lipid concentrations were compared in a crossover study. Each bran (123 g oat bran or 54 g wheat bran) added nearly 18 g of nonstarch polysaccharide to a background diet containing about 10 g nonstarch polysaccharide. Twenty-three men (average plasma cholesterol level = 5.84 mmol/L, and low-density-lipoprotein (LDL) cholesterol level = 4.11 mmol/L) were randomly assigned to either the oat or wheat bran diet for 4 weeks and then changed to the alternate bran diet for a similar period. The oat bran diet produced significantly lower levels of plasma total cholesterol and LDL cholesterol: 5.65 +/- 0.16 and 3.88 +/- 0.15 mmol/L (mean +/- standard error) for oat bran vs 5.89 +/- 0.16 and 4.11 +/- 0.16 mmol/L for wheat bran. Food intake diaries showed that average consumption of total fat and saturated fat was identical during the two test periods, which excluded displacement of fat as an explanation for lowering of plasma cholesterol by oat bran. Our results indicate that in mildly hypercholesterolemic men, a diet high in soluble oat fiber can significantly lower plasma total cholesterol and LDL cholesterol and thus potentially lower the risk of coronary heart disease.     

Effects of vitamin C on high-density lipoprotein cholesterol and blood pressure.

Diet has been linked to cardiovascular disease risk by its influence on low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and blood pressure (BP). Recent evidence suggests that vitamin C may play a role in regulation of cholesterol and BP. The cross-sectional relationships of plasma ascorbic acid (PAA) with cholesterol and BP are described in three Boston area samples: 1) 249 males and 447 females (aged 60-100 years), 2) 100 Chinese-American males and 159 Chinese-American females (aged 60-96 years), and 3) 225 male and 192 female participants (aged 20-60 years) in a randomized field trial of vitamin C supplementation. Results indicate 3.7-9.5% higher levels of HDL-C, 4.1% lower levels of LDL-C, and 1.9-5.5% lower levels of BP with each 30 mumol/L increment in PAA. These relationships may be stronger at lower levels of PAA.     

Clinical characteristics and pharmacokinetics of purified soy isoflavones: single-dose administration to healthy men.

BACKGROUND: Soy isoflavones are potential cancer chemoprevention treatments. OBJECTIVE: We conducted safety studies of purified unconjugated genistein, daidzein, and glycitein, and defined pharmacokinetic parameters for their absorption and metabolism. DESIGN: Thirty healthy men ingested a single dose of 1 of 2 isoflavone preparations purified from soy. The delivered doses of genistein (1, 2, 4, 8, or 16 mg/kg body wt) were higher than those previously administered to humans. Formulation A was composed of 90 +/- 5% genistein, 10% daidzein, and 1% glycitein. Formulation B was composed of 43% genistein, 21% daidzein, and 2% glycitein. RESULTS: We observed no clinically significant behavioral or physical changes after treatment. We observed elevations in lipoprotein lipase and hypophosphatemia that were possibly related to the treatment but that were associated with no clinical toxicity. Considerable quantities of isoflavones were excreted in urine as conjugates. The terminal elimination rate, elimination half-life, area under the curve, maximum plasma concentration, apparent systemic clearance, and volume of distribution were estimated for genistein and daidzein. The mean elimination half-lives with both formulations were 3.2 h for free genistein and 4.2 h for free daidzein. The mean pseudo half-lives were 9.2 h for total genistein and 8.2 h for total daidzein. CONCLUSIONS: Dietary supplements of purified unconjugated isoflavones administered to humans in single doses exceeding normal dietary intake manyfold resulted in minimal clinical toxicity. Genistein and daidzein (free and total) were rapidly cleared from plasma and excreted in urine.     

Effects of vitamin E deficiency on the distribution of cholesterol in plasma lipoproteins and the activity of cholesterol 7 alpha-hydroxylase in rabbit liver

Vitamin E-deficient rabbits with signs of muscular dystrophy showed accumulation of cholesterol in muscle as well as elevation of plasma cholesterol. The increase in plasma cholesterol was detected in low density lipoprotein (LDL) and very low density lipoprotein (VLDL) but not in high density lipoprotein (HDL) fractions of plasma lipoproteins. In liver, the activity of cholesterol 7 alpha-hydroxylase, the key enzyme involved in degradation of cholesterol, was approximately one-fifth that of control rabbits. Cytochrome P-450 level of liver microsomes was also reduced significantly. These results suggested that accumulation of cholesterol observed in dystrophic muscle of vitamin E-deficient rabbits may be due to an increase in LDL and VLDL cholesterol, the plasma lipoproteins carrying cholesterol to peripheral tissue, and to a decrease in cholesterol 7 alpha-hydroxylase activity, whose activity may have been affected by the reduced level of cytochrome P-450.