Association between carbohydrate intake and serum lipids

BACKGROUND: The effect of dietary carbohydrate on blood lipids has received considerable attention in light of the current trend in lowering carbohydrate intake for weight loss. OBJECTIVES: To evaluate the association between carbohydrate intake and serum lipids. METHODS: Blood samples and 24-hour dietary and physical activity recall interviews were obtained from each subject at quarterly intervals for five consecutive quarters between 1994 and 1998 from 574 healthy adults in Central Massachusetts. Relationships between serum lipids and dietary carbohydrate factors were assessed using linear mixed models and adjusting for other risk factors known to be related to blood lipids. Both cross-sectional and longitudinal results were reported. RESULTS: Cross-sectional analysis results from this study suggest that higher total carbohydrate intake, percentage of calories from carbohydrate, glycemic index (GI) and/or glycemic load (GL) are related to lower high-density lipoprotein cholesterol (HDL-C) and higher serum triacylglycerol levels, while higher total carbohydrate intake and/or GL are related to lower total and low-density lipoprotein cholesterol (LDL-C) levels. In a one-year longitudinal analysis, GL was positively associated with total and LDL-C levels, and there was an inverse association between percentage of calories from carbohydrate and HDL-C levels. CONCLUSIONS: Results suggest that there is a complex and predominantly unfavorable effect of increased intake of highly processed carbohydrate on lipid profile, which may have implications for metabolic syndrome, diabetes, and coronary heart disease. Further studies in the form of randomized controlled trials are required to investigate these associations and determine the implications for lipid management.     

Carbohydrate intake and obesity

The prevalence of obesity has increased rapidly worldwide and the importance of considering the role of diet in the prevention and treatment of obesity is widely acknowledged. This paper reviews data on the effects of dietary carbohydrates on body fatness. Does the composition of the diet as related to carbohydrates affect the likelihood of passive over-consumption and long-term weight change? In addition, methodological limitations of both observational and experimental studies of dietary composition and body weight are discussed. Carbohydrates are among the macronutrients that provide energy and can thus contribute to excess energy intake and subsequent weight gain. There is no clear evidence that altering the proportion of total carbohydrate in the diet is an important determinant of energy intake. However, there is evidence that sugar-sweetened beverages do not induce satiety to the same extent as solid forms of carbohydrate, and that increases in sugar-sweetened soft drink consumption are associated with weight gain. Findings from studies on the effect of the dietary glycemic index on body weight have not been consistent. Dietary fiber is associated with a lesser degree of weight gain in observational studies. Although it is difficult to establish with certainty that fiber rather than other dietary attributes are responsible, whole-grain cereals, vegetables, legumes and fruits seem to be the most appropriate sources of dietary carbohydrate.     

Carbohydrate intake during exercise and performance

It is generally accepted that carbohydrate (CHO) feeding during exercise can improve endurance capacity (time to exhaustion) and exercise performance during prolonged exercise (>2 h). More recently, studies have also shown ergogenic effects of CHO feeding during shorter exercise of high intensity ( approximately 1 h at >75% of maximum oxygen consumption). During prolonged exercise the mechanism behind this performance improvement is likely to be related to maintenance of high rates of CHO oxidation and the prevention of hypoglycemia. Nevertheless, other mechanisms may play a role, depending on the type of exercise and the specific conditions. The mechanism for performance improvements during higher-intensity exercise is less clear, but there is some evidence that CHO can have central effects. In the past few years, studies have investigated ways to optimize CHO delivery and bioavailability. An analysis of all studies available shows that a single CHO ingested during exercise will be oxidized at rates up to about 1 g/min, even when large amounts of CHO are ingested. Combinations of CHO that use different intestinal transporters for absorption (e.g., glucose and fructose) have been shown to result in higher oxidation rates, and this seems to be a way to increase exogenous CHO oxidation rates by 20% to 50%. The search will continue for ways to further improve CHO delivery and to improve the oxidation efficiency resulting in less accumulation of CHO in the gastrointestinal tract and potentially decreasing gastrointestinal problems during prolonged exercise.     

A randomized controlled trial of dietary fiber intake on serum lipids

OBJECTIVE: Clinical trials have indicated that water-soluble fiber from oats reduces serum cholesterol among hypercholesterolemic patients on a low-fat diet. We examined the effect of dietary fiber intake on serum lipids among persons without hypercholesterolemia. DESIGN: Randomized controlled trial. SETTING AND SUBJECTS: We recruited 110 participants who were aged 30-65 years and had a serum cholesterol level < 240 mg/dl from community. INTERVENTION: Study participants were randomly assigned to receive 8 g per day of water-soluble fiber from oat bran or a control intervention. RESULTS: At baseline, the mean levels of serum cholesterol and other measured variables were comparable between the high-fiber and control groups. Over the 3-month intervention, mean changes (95% confidence interval (CI)) in total, HDL-, and LDL-cholesterol were -2.42 mg/dl (-8.90 to 4.05 mg/dl; P = 0.46), -0.24 mg/dl (-2.19 to 1.71 mg/dl; P = 0.81), and -1.96 mg/dl (-7.32 to 3.40 mg/dl; P = 0.47) in the fiber group and -0.02 mg/dl (-5.29 to 5.26 mg/dl; P = 0.99), 1.42 mg/dl (-0.74 to 3.59 mg/dl; P = 0.19), and -0.64 mg/dl (-5.30 to 4.03 mg/dl; P = 0.79) in the control group, respectively. The net changes (95% confidence interval) in total, HDL-, and LDL-cholesterol were -2.40 mg/dl (-10.6 to 5.81 mg/dl; P = 0.56), -1.66 mg/dl (-4.55 to 1.22 mg/dl; P = 0.26) and -1.33 mg/dl (-8.33 to 5.68 mg/dl; P = 0.71), respectively. CONCLUSIONS: Our study does not support the hypothesis that water-soluble fiber intake from oat bran reduces total and LDL-cholesterol in study participants with a normal serum cholesterol level.     

Food intake, serum lipids and amino acids of school children in agricultural communities in Japan

OBJECTIVE: To investigate the correlation among serum lipids, amino acids and diet of children in Japan where the mortality of ischemic heart disease is still very low. DESIGN: Cross-sectional study. SETTING: Two towns in Shimane prefecture, typical mountainous agricultural communities in the western part of the mainland of Japan. SUBJECTS: 514 children (10-15 y) in the communities were recruited. RESULTS: The mean cholesterol levels ranged from 3.9 to 4.4 mmol/l for boys and from 4.3 to 4.5 mmol/l for girls, and serum cholesterol level fell with age in boys. Serum cholesterol level of girls rose once between 11 and 13 y and fell gradually. Fish intake was positively correlated with serum omega-3 series fatty acids. Milk intake was negatively and soybean intake was positively correlated with omega-3/omega-6 series fatty acids ratio. Serum branched-chain amino acids were correlated negatively with serum polyunsaturated/saturated fatty acids ratio. CONCLUSIONS: Serum cholesterol level of children in agricultural communities in Japan has risen, and is probably affected by the change of food intake. Promoting the intake of soybean and fish, which are traditional Japanese foods, will be important in preventing atherosclerosis and ischemic heart disease. Attention should be paid to the relationship between branched-chain amino acids level in blood and fatty acids metabolism to verify the mechanism of the progress of atherosclerosis.     

Caffeine, blood pressure, and serum lipids

To study the effects of caffeine on serum lipids and blood pressure, we conducted a double-blind, randomized trial with two parallel groups in 69 young, healthy subjects. After a 3-wk run-in period, subjects were randomly assigned to one of two groups receiving either 4-6 140-mL cups filtered decaffeinated coffee per day and an equal number of pills containing 75 mg caffeine or 4-6 140-mL cups filtered decaffeinated coffee per day and an equal number of placebo pills, for 9 wk. In both groups caffeine intake from other sources was not allowed. The main finding of this study is that abstinence from caffeine for a period of 9 wk has no effect on either serum lipids or blood pressure.     

Carbohydrate intake and HDL in a multiethnic population

BACKGROUND: Ethnic differences in serum lipids are not explained by genetics, central adiposity, lifestyle, or diet, possibly because dietary carbohydrate has not been considered. OBJECTIVE: The aim was to evaluate the relation between carbohydrate intake and HDL and triacylglycerol concentrations in a multiethnic population. DESIGN: We conducted a population-based cross-sectional study of 619 Canadians of Aboriginal, South Asian, Chinese, and European origin with no previously diagnosed medical conditions. Energy-adjusted carbohydrate intake was measured by a validated food-frequency questionnaire. RESULTS: South Asians consumed the most carbohydrate, followed by European, Aboriginal, and Chinese persons. Mean (95% CI) HDL concentrations in the lowest and highest categories of carbohydrate intake after adjustment for age, sex, ethnicity, physical activity, smoking, the waist-to-hip ratio, body mass index, alcohol intake, and intakes of total energy, protein, and fiber were 1.21 mmol/L (1.16, 1.27 mmol/L) and 1.08 mmol/L (1.02, 1.13 mmol/L), respectively, and HDL cholesterol was significantly (P < 0.01) higher in the lowest tertile of carbohydrate intake than in the highest tertile. High carbohydrate intake was associated with higher fasting triacylglycerols (P = 0.04); the adjusted mean fasting triacylglycerol concentrations in the lowest and highest categories of carbohydrate intake were 1.43 mmol/L (1.28, 1.60 mmol/L) and 1.71 mmol/L (1.57, 1.87 mmol/L), respectively. Fewer servings of sugar-containing soft drinks, juices, and snacks were associated with higher HDL (P for trend = 0.02); the multivariate-adjusted mean HDL in the lowest and highest categories of carbohydrate intake was 1.22 mmol/L (1.17, 1.27 mmol/L) and 1.11 mmol/L (1.06, 1.26 mmol/L), respectively. CONCLUSIONS: Differences in HDL and triacylglycerols observed in different ethnic groups may be due in part to carbohydrate intake. Reducing the frequency of intake of sugar-containing soft drinks, juices, and snacks may be beneficial.     

Clinical effects of mandibular fixation on cholesterol intake and serum lipids: a case study

With cholesterol and saturated fat intake strictly controlled and monitored, the opportunity arose to study the effect of stress on the elevation of cholesterol levels (7). Results indicate significant increase in fasting lipids preoperatively (Table 1). Postoperatively, lipid levels dropped immediately and leveled out to a normal range for this patient and were maintained through the 6-month follow-up blood analysis. As lipids increased, the cardiovascular risk factors remained fairly consistent because of a similar elevation of all lipids. This supports the research that stress releases catecholamines, which raise free fatty acid levels in the blood stream (8,9). This case study does suggest that there is a relationship between elevated serum lipid levels and emotional stress (10). A total liquid diet for 6 to 8 weeks can modify cholesterol intake. This case study is unique because the patient consumed only low-cholesterol, low-saturated fat foods and liquids and nutritional supplements and was acutely aware of meeting nutritional requirements (6). The average patient undergoing oral surgery with mandibular fixation typically selects whole milk products, ice cream, and other high-cholesterol liquids in order to increase total caloric intake.     

The effect of milk and skim milk intake on serum lipids and apoproteins in young females

The effect of milk and skim milk intake on serum lipid and apoprotein levels was investigated in young females with consideration of each subject's menstrual period. When milk and dairy products were not allowed, the serum cholesterol concentration tended to decrease in high density lipoprotein (HDL) and very low density lipoprotein (VLDL), the triglyceride concentration tended to increase in HDL and low density lipoprotein (LDL), the phospholipid concentration showed no change, and the apoB, apoC-III and apoE significantly decreased. In the milk group, VLDL cholesterol and phospholipid concentrations were increased with a significant increase in the apoB concentration after intake of 200 ml/day of milk for one menstrual period, and these levels did not change when the milk intake was doubled. VLDL phospholipid increased and apoE decreased after the intake of 20 g/day of skim milk, and LDL cholesterol and HDL phospholipid concentrations tended to decrease when the skim milk intake was doubled.     

补钙对高胆固醇血症女性血脂影响

目的 观察钙剂补充对人体血浆胆固醇浓度及血脂状况的影响,为合理调整人群的膳食结构和营养素摄入量,降低血浆胆固醇浓度,防治心血管疾病提供基础依据.方法 在普通膳食的基础上,对10名高胆固醇血症女性每人每天补充1000 mg钙(碳酸钙),连续28d,以未补充钙剂的10名高胆固醇血症女性为对照,观察血脂各项指标的变化.结果 补钙结束时,补钙组各项血脂指标均低于对照组,但差异无统计学意义.自身对照的结果表明,补钙组除载脂蛋白A(ApoA)外,其他各项血脂指标的值均明显低于补钙前(P＜0.05),尤其是血浆总胆固醇浓度由补钙前的(5.78±0.65)mmol/L降至(5.16±0.61)mmol/L;而对照组除ApoA值明显增高外(P＜0.05),其他各项血脂指标均无明显改变.结论 在本实验条件下,每天为高胆固醇血症者补充1000mg钙有利于改善其血脂状况,特别是有利于降低血浆中胆固醇水平.     

The effect of milk and skim milk intake on serum lipids and apoproteins in postmenopausal females.

The effects of milk and skim milk intake on serum lipids, apoprotein levels and fatty acid composition were investigated in postmenopausal females. After a 25-day intake of 200 ml/day of whole milk, the milk group had increased HDL and LDL cholesterol levels, with a slight decrease in the proportion of 18:0 fatty acids in the phospholipid fraction. The skim milk group, which had consumed 20 g/day of skim milk for 25 days, showed no changes. After intake of 400 ml/day of whole milk for 29 days, LDL, HDL and total cholesterol concentrations were even more increased and the VLDL-phospholipid concentration was decreased, with significant increases in apoA-I, apoA-II and apoB concentrations. In the skim milk group, consuming 40 g of skim milk per day for 29 days, total cholesterol, atherogenic index, HDL-triglyceride concentrations were decreased and HDL-phospholipid, apoA-I and apoA-II concentrations were increased. Daily skim milk consumption, which is effective in preventing osteoporosis, and careful selection of foods should be recommended for Japanese postmenopausal women who consume more than 200 ml/day of whole milk.     

Effect of a cooperative extension nutrition and exercise program for older adults on nutrition knowledge,dietary intake,anthropometric measurements,and serum lipids

The purpose of this study was to assess the impact of a nutrition and fitness program for older adults on their nutritional status. Twenty-four adult volunteers between the ages of 60 and 88 participated in a nutrition and exercise program. Pre- and post-program data were collected on nutrition knowledge, dietary intake using a 24-hour recall procedure, anthropometric values, serum lipids, and exercise patterns. After initial data collection, the subjects participated in a 12-week nutrition program. Nutrition knowledge scores increased significantly, with an average increase of 12%. Total dietary intake of fat did not significantly change following the program. However, there was a significant change in the type of fat consumed: saturated fat intake decreased and polyunsaturated fat intake increased. Percent of calories from carbohydrate, protein and fat averaged 51%, 19% and 30%, respectively. Body weight significantly decreased; however, there was not a significant decrease in % bodyfat, % overfat and pounds overweight. Both systolic and diastolic blood pressures significantly decreased, as did total cholesterol, LDL cholesterol and triglycerides. HDL cholesterol and % HDL cholesterol significantly increased. The number of days per week exercised, time exercised, and exercise intensity also significantly increased.     

调整饮食结构对痛风伴超重者血尿酸、血脂、肾功能及结局的影响

目的 探讨调整三大供能营养素比例及构成兼减轻体重对痛风伴超重者血尿酸、血脂水平及肾功能和结局的影响.方法 将6个月前至少经历1次痛风发作的非糖尿病男性伴超重的痛风患者67例纳入研究,按照随机数字表法将患者分为高蛋白研究组(每日给予能量6276 kJ,其中碳水化合物40％、蛋白质30％、脂肪30％,复合碳水化合物替代精制碳水化合物,单不饱和脂肪、多不饱和脂肪酸替代饱和脂肪酸,不计嘌呤含量)及低嘌呤对照组(热量同高蛋白研究组,其中碳水化合物60％、蛋白质10％、脂肪30％,嘌呤＜150 mg/d),研究开始及6个月后分别取血样检测血尿酸(UA)、血清总胆固醇(TC)、三酰甘油(TG)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、空腹血糖(FBG)、血肌酐(SCr)、血尿素氮(BUN)、白蛋白(ALB)、血清总蛋白(TP)、血红蛋白(Hb)水平及6个月内痛风发作次数.结果 61例患者完成研究(脱落率9.0％).膳食干预6个月后,患者体重减轻[(65.75±3.26)比(69.31±7.78)kg,P=0.043]、痛风发作次数减少(17比28次,P=0.000).与低嘌呤对照组比较,高蛋白研究组UA[(420.25±36.78)比(466.81±41.97)μmol/L,P=0.000)]、TC[(5.69±0.46)比(6.49±1.04)mmol/L,P=0.007)]、TG[(2.15±0.54)比(3.13±0.62)mmol/L,P=0.000)]和FBG[(5.63±0.82)比(6.49±0.64)mmol/L,P=0.000)]显著下降,HDL-C[(1.24 ±0.22)比(0.89±0.26)mmol/L,P=0.000)]、ALB[(41.56±5.37)比(37.08±5.94)g/L,P=0.014)]、TP[(72.97±5.41)比(67.27±7.87)g/L,P=0.005)]和Hb[(142.86±12.31)比(114.25±12.98)g/L,P=0.001)]显著升高.两组LDL-C[(3.55 ±0.80)比(3.73±0.72)mmol/L,P=0.445)]、SCr[(96.63±16.97)比(94.28±13.35)μmol/L,P=0.597)]和BUN[(4.89±1.25)比(4.46±1.21)mmol/L,P=0.208)]差异无统计学意义.干预后高蛋白研究组和低嘌呤对照组痛风发作次数分别下降48.48％和22.22％,两组痛风发作次数差异具有统计学意义(P=0.000).结论 调整痛风患者宏量营养素摄入比例兼减轻体重有利于降低患者UA水平、调节血脂、改善营养状况并减少痛风发作次数.     

大豆蛋白和高钙摄入对高血胆固醇模型大鼠血脂水平的影响

目的探讨膳食大豆蛋白和/或高钙摄入对高血胆固醇模型大鼠血浆胆固醇及有关血脂指标的影响.方法用含5%猪油、1%胆固醇和0.25%胆碱的高脂饲料喂饲健康Wistar雌性大鼠,经14d诱发高血胆固醇以后,测血浆总胆固醇(TC),总甘油三酯(TG),高密度脂蛋白胆固醇(HDL-C)和载脂蛋白B(ApoB100)的浓度.然后,按体重和血浆胆固醇浓度将动物均衡分为4组,以2×2析因设计,分别喂饲含有酪蛋白和大豆分离蛋白及正常钙(0.59%)和高钙水平(1.12%)的纯合成高脂饲料.经21d喂养后,采血,测定指标同前.实验结果用SPSS统计软件进行方差分析.结果经14d诱导高血脂后,实验模型大鼠的TC水平为(4.10±1.11)mmol/L(n=24),而喂饲正常饲料的阴性对照鼠仅为(1.92±0.28)mmol/L(n=8),升高了2.14倍.又经21d喂饲含有处理因素的饲料后,酪蛋白组,酪蛋白加钙组,大豆蛋白组和大豆蛋白加钙组大鼠的TC水平分别为(10.56±2.74,7.99±2.19,5.48±0.51和6.81±0.98)mmol/L;ApoB100为(0.46±0.14,0.31±0.12,0.17±0.07和0.21±0.05)g/L.同酪蛋白组相比,其他3组动物的TC和ApoB100浓度显著降低.而各组间TG和HDL-C的变化均无显著性.结论膳食大豆蛋白和/或高钙摄入均可降低高血胆固醇模型大鼠的TC和ApoB100浓度,但对TG和HDL-C的作用不明显.大豆蛋白是这种作用的主要因素,但同时存在大豆蛋白和高钙摄入的相互作用.膳食大豆蛋白和高钙摄入的降血胆固醇机制还需要进一步探讨和研究.     

Energy intake and the appearance of 5,8,11-eicosatrienoic acid in serum lipids during parenteral nutrition without fat

During parenteral nutrition without fat, biochemical changes in fatty acid composition of serum lipids may occur, such as a decrease in the concentration of linoleic and arachidonic acid and an increase of 5,8,11-eicosatrienoic acid. In various reports on essential fatty acid deficiency in parenteral nutrition, the rates and degrees of these changes in fatty acid composition of serum lipids are different. We have tested the hypothesis that a relationship exists between the energy intake and the increase in 5,8,11-eicosatrienoic acid in parenteral nutrition without fat. The hypothesis is based on the assumption that mobilization of lipids from body fat, and thus of stored essential fatty acids, only takes place when energy intake is below requirements. Seventeen patients with gastrointestinal diseases were fed parenterally without fat during 1 to 5 weeks (mean 3.5 week). The energy supply to the patients varied from 88 to 222 kilo Joules per kilogram per day. In all patients, the fatty acid pattern of the serum phospholipid fraction was determined weekly. It appeared that those patients with the highest energy intake per kilogram body weight showed the lowest increase in 5,8,11-eicosatrienoic acid. In ten patients, energy was given as glucose and fructose, in seven patients as sorbitol. The type of carbohydrate investigated did not influence the changes in the fatty acid pattern. Results show further that the individual values of the concentrations of 5,8,11-eicosatrienoic acid and of arachidonic acid provide more information concerning the essential fatty acid status of a patient than the commonly used ratio of these two fatty acids.