Changing concepts in lipid nutrition in health and disease

Fat remains a hot topic because of concerns over associations between consumption of fats and the incidence of some chronic conditions including coronary artery disease, diabetes, cancer and obesity. Dietary fats serve multiple purposes. The effects of dietary fats generally reflect the collective influences of multiple fatty acids in the diet or food. This presentation highlights some recent developments on the role of dietary fats and oils in health and disease. Debate continues over the role of dietary modification in coronary prevention by lipid lowering. The degree to which a recommended diet will result in health benefits for an individual is difficult to predict, because the outcome will depend on the influence of other factors such as a person's genetic constitution, level of physical activity and total diet composition. There can now be little doubt about the importance of genetic factors in the etiology of cardiovascular disease, diabetes, obesity and cancer. The importance of antioxidant status in the prevention of cardiovascular disease as well as many cancers is being increasingly recognised. It is now evident that not all saturated fatty acids are equally cholesterolemic. Recent accounts evaluating palm oil's effects on blood lipids and lipoproteins suggest that diets incorporating palm oil as the major dietary fat do not raise plasma total and LDL cholesterol levels to the extent expected from its fatty acid composition. Palm oil is endowed with a good mixture of natural antioxidants and together with its balanced composition of the different classes of fatty acids, makes it a safe, stable and versatile edible oil with many positive health and nutritional attributes. In recent times, adverse health concerns from the consumption of trans fatty acids arising from hydrogenation of oils and fats have been the subject of much discussion and controversy. Trans fatty acids when compared with cis fatty acids or unhydrogenated fats have been shown to lower serum HDL cholesterol, raise serum LDL cholesterol and when substituted for saturated fatty acids, increase lipoprotein Lp (a) level, an independent risk factor for the development of coronary heart disease. The idea of which foods, nutrients and supplements are "healthy" is often being amended as new scientific data is presented and then simplified for the consumers. What was once perceived as a healthy diet is often no longer considered as such and vice versa. Dietary recommendations have to change with time and the evidence available. Nutritional recommendations should encourage eating a great variety of nutrient sources within our food supply in moderation. Various lifestyle options to improve health should also be promoted.     

Fatty acid composition and possible health effects of coconut constituents

The link between excessive consumption of dietary saturated fats and coronary heart disease (CHD) is now well established. Because of its high content of saturated fatty acids, the consumption of foods containing coconut oil may therefore be a risk factor for CHD. While the fatty acid composition of coconut oil is well established, relatively little is known about the other constituents of coconut: the milk, water, cream and meat fractions. In this study, we show that while the water fraction is low in lipid content, the milk contains about 24% of the fat content of oil and the cream and meat fractions about 34%. The other coconut constituents contain significant amounts of medium-chain triglycerides that are formed from fatty acids of chain length 8:0 to 14:0. It is these fatty acids, primarily 14:0, that are thought to be atherogenic. On the other hand, medium-chain triglycerides may be advantageous under some circumstances in that they are absorbed intact and do not undergo degradation and re-esterification processes. As a result, medium-chain triglycerides provide a ready source of energy and may be useful in baby foods or in diet therapy. Nevertheless, the possible negative effects of the saturated fatty acids and the absence of the essential fatty acid linolenic acid from all coconut constituents suggest that the coconut milk, oil and cream should not be used on a regular basis in adults.     

Choice of cooking oils--myths and realities

In contrast to earlier epidemiologic studies showing a low prevalence of atherosclerotic heart disease (AHD) and type-2 dependent diabetes mellitus (Type-2 DM) in the Indian subcontinent, over the recent years, there has been an alarming increase in the prevalence of these diseases in Indians--both abroad and at home, attributable to increased dietary fat intake. Replacing the traditional cooking fats condemned to be atherogenic, with refined vegetable oils promoted as "heart-friendly" because of their polyunsaturated fatty acid (PUFA) content, unfortunately, has not been able to curtail this trend. Current data on dietary fats indicate that it is not just the presence of PUFA but the type of PUFA that is important--a high PUFA n-6 content and high n-6/n-3 ratio in dietary fats being atherogenic and diabetogenic. The newer "heart-friendly" oils like sunflower or safflower oils possess this undesirable PUFA content and there are numerous research data now available to indicate that the sole use or excess intake of these newer vegetable oils are actually detrimental to health and switching to a combination of different types of fats including the traditional cooking fats like ghee, coconut oil and mustard oil would actually reduce the risk of dyslipidaemias, AHD and Type-2 DM.     

不同脂肪酸饮食对大鼠肝脏xbp-1的影响

目的:探讨饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸饮食对大鼠肝脏X盒结合蛋白-1(XBP-1)的影响。方法:48只雄性Wistar大鼠随机分为4组:正常对照组(N组)、饱和脂肪酸饮食组(S组)、单不饱和脂肪酸饮食组(M组)、多不饱和脂肪酸饮食组(P组)。正常对照组给基础饲料(脂肪占10.3%);饱和脂肪酸饮食组的饲料是在基础饲料中添加15%猪油;单不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%茶油;多不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%豆油(脂肪占35.4%)。8周后4组各随机选8只大鼠行高胰岛素-正葡萄糖钳夹试验,同时留取空腹状态血清测定血脂、胰岛素等指标。肝脏XBP-1蛋白表达分别用Western blot法和免疫组化法测定。结果:①实验第8周末,与N组相比,P、M、S组大鼠进食量有所减少(P<0.05)。除外进食量的影响,与N组相比,S组血清总胆固醇(TC)、甘油三酯(TG)升高(P<0.05),M、P组差异无统计学意义(P>0.05);S、P组空腹胰岛素(FINS)、空腹血糖(FBG)升高,葡萄糖输注率(GIR)明显下降(P均<0.05),但S、P两组间无统计学意义(P>0.05);M...     

The role of essential fatty acids and prostaglandins.

The FAO/WHO Rome Report recommended an increase in the consumption of fat in countries where malnutrition is endemic; for maintenance, 3% of the dietary energy as essential fatty acids (EFA) may be adequate; in pregnancy and lactation an additional 1.5 to 2.4% energy as EFA is needed. For population at high risk for atherosclerosis and coronary heart disease (CHD) the recommendations were to decrease saturated fat in particular and increase EFA intake in the diet, reduce sugar, alcohol and cholesterol. These recommendations were similar to those of the Royal College of Physicians but the report went further by saying that EFA loss through industrial hydrogenation should be minimized and associated nutrients such as vitamin E and carotene should be restored if lost in processing. In terms of production, they asked for an increase in edible plant oils in developing countries and requested that intensive animal feeding and breeding should be corrected to avoid the excess accumulation of saturated fats. In addition, the Rome Report requested meaningful labelling of amounts and quality of fat in foods containing added fats. The basic aims of the Report were to state the position of lipid nutrition. The issue of the nutrient correction in terms of CHD cannot properly be discussed without taking into account the essential components which are needed for the integrity and development of the vascular system.     

膳食脂肪酸摄入及构成与心脑血管疾病相关性的研究进展

心脑血管疾病日趋严重地威胁着人类的健康和生命,而膳食中饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)、多不饱和脂肪酸(PUFA)的种类、数量及构成比与心脑血管疾病关系密切.膳食脂肪与心脑血管疾病的相互关系倍受国内外学者的关注.对各种膳食脂肪酸与心脑血管疾病关系的研究进展进行综述,提出防治心脑血管疾病较合理的膳食脂肪酸摄入原则.     

Trans fatty acids,HDL-cholesterol,and cardiovascular disease. Effects of dietary changes on vascular reactivity

A high consumption of trans fatty acids increases the risk of cardiovascular disease (CVD). We investigated whether this increase in risk was due to the decrease in serum HDL-cholesterol by trans fatty acids, because low concentrations of serum HDL-cholesterol also increase risk of CVD. Flow-mediated vasodilation (FMD) was used as an endpoint in dietary interventions that were designed to change the concentration of serum HDL-cholesterol within 4 weeks in healthy volunteers. Replacement of 10% of energy from saturated by trans fatty acids decreased serum HDL-cholesterol by 21 % and impaired FMD. However, a replacement of monounsaturated fats by carbohydrates did not impair FMD, although it decreased serum HDL-cholesterol by 13%. Acute postprandial impairments of FMD by either trans fats or saturated fats were not found, suggesting that long-term effects are responsible for the detrimental effect of trans fats on health. However, the role of serum HDL-cholesterol appears to be less than we expected.     

Fat Profile of Jamaican Ackees,Oleic Acid Content and Possible Health Implications

Objective:

To re-investigate the composition of ackee oil and unequivocally determine its principal fatty acid components.

Methods:

Oil was extracted from the edible portion of ackees harvested in three different studies (I–III) by several analysts; studies I and II utilized composite samples from several trees while study III consisted of ackees from seven separate trees. The oils were either saponified and methylated or trans-methylated and the fatty acid methyl ester content analysed by gas chromatography-mass spectrometry (GC-MS). Relative fatty acid composition was quantified based on chromatographic peak areas while fatty acids were identified by mass spectrometry. The degree of unsaturation of the ackee oils was characterized by determination of the iodine value.

Results:

Gas chromatography-mass spectrometry data from the three studies were assessed. Relative fatty acid composition for the ackee oils was consistent across the three studies. The major fatty acid components were oleic acid (55.44%), palmitic acid (25.57%) and stearic acid (12.59%); linoleic acid was present in minor to undetectable amounts. An iodine value of 49 was determined which is consistent with the high oleic acid content of the ackee oil.

Conclusion:

The ackee samples analysed were rich in the monounsaturated fatty acid (MUFA) oleic acid. Consideration should be given to potential protective health effects of diets which include ackee.     

Dietary prevention of coronary heart disease. Effect of dietary fats on arterial thrombosis.

Epidemiological studies indicate that dietary saturated fats are implicated in coronary heart disease (CHD). Human prospective studies have shown that diets low in long chain saturated fatty acids and enriched in linoleic acid are beneficial in CHD-prevention. Experiments in animals have shown that such diets diminish atherosclerosis and the tendency to arterial thrombosis; they also lower the ability of platelets to aggregate in animals and in man. The mechanisms by which these diets produce these effects are not yet completely understood. Platelets and vascular prostaglandin-like substances may be involved as well as platelet membrane fluidity and platelet coagulant activities. On the basis of the available evidence, measures to decrease the intake of long chain saturated fatty acids (concomitant with an enhanced consumption of linoleic acid-rich products) are justified. Although certain marine oils may also have anti-thrombotic properties the possibility of undesirable side effects compels extensive investigation before their wide-spread use can be recommended.     

Effects of avocado as a source of monounsaturated fatty acids on plasma lipid levels.

To examine the effects of avocado on plasma lipid concentrations, a three-diet trial involving 16 healthy volunteers was carried out. A diet rich in monounsaturated fatty acids using avocado as their major source (30% of the total energy was consumed as fat: 75% of the total fat from the avocado), with restriction of saturated fats and less than 300 mg of cholesterol per day was evaluated. Subjects also were in a free-diet period with the addition of the same amount of avocado. Finally, volunteers received a low-saturated fat diet without avocado. The first and third diets were designed to simulate a usual diet and volunteers carried on their normal activities during the trial, only the three daily meals were eaten in our clinical unit. Diets lasted 2 weeks and they were assigned in a randomized order. In both rich-monounsaturated fat (RMF) and low-saturated fat (LSF) diets, there were similar reductions in the plasma total cholesterol and low-density lipoprotein cholesterol levels. The levels of high-density lipoprotein cholesterol significantly decreased (p < 0.05) after 2 weeks of the LSF and free monounsaturated-enriched (FME) diets. The plasma triacyglycerol levels lessened after RMF and FME diets, while LSF diet increased them. In total cholesterol and in low-lipoprotein cholesterol levels, there were statistically significant differences between the FME and the LSF diet periods. Avocado is an excellent source of monounsaturated fatty acid in diets designed to avoid hyperlipidemia without the undesirable effects of low-saturated fat diets on HDL-cholesterol and triacylglycerol concentrations.     

Optimal diets for prevention of coronary heart disease

Context  Coronary heart disease (CHD) remains the leading cause of mortality in industrialized countries and is rapidly becoming a primary cause of death worldwide. Thus, identification of the dietary changes that most effectively prevent CHD is critical. Objective  To review metabolic, epidemiologic, and clinical trial evidence regarding diet and CHD prevention. Data Sources and Study Selection  We searched MEDLINE through May 2002 for epidemiologic and clinical investigations of major dietary factors (fat, cholesterol, omega-3 fatty acids, trans-fatty acids, carbohydrates, glycemic index, fiber, folate, specific foods, and dietary patterns) and CHD. We selected 147 original investigations and reviews of metabolic studies, epidemiologic studies, and dietary intervention trials of diet and CHD. Data Extraction  Data were examined for relevance and quality and extracted by 1 of the authors. Data Synthesis  Compelling evidence from metabolic studies, prospective cohort studies, and clinical trials in the past several decades indicates that at least 3 dietary strategies are effective in preventing CHD: substitute nonhydrogenated unsaturated fats for saturated and trans-fats; increase consumption of omega-3 fatty acids from fish, fish oil supplements, or plant sources; and consume a diet high in fruits, vegetables, nuts, and whole grains and low in refined grain products. However, simply lowering the percentage of energy from total fat in the diet is unlikely to improve lipid profile or reduce CHD incidence. Many issues remain unsettled, including the optimal amounts of monounsaturated and polyunsaturated fats, the optimal balance between omega-3 and omega-6 polyunsaturated fats, the amount and sources of protein, and the effects of individual phytochemicals, antioxidant vitamins, and minerals. Conclusions  Substantial evidence indicates that diets using nonhydrogenated unsaturated fats as the predominant form of dietary fat, whole grains as the main form of carbohydrates, an abundance of fruits and vegetables, and adequate omega-3 fatty acids can offer significant protection against CHD. Such diets, together with regular physical activity, avoidance of smoking, and maintenance of a healthy body weight, may prevent the majority of cardiovascular disease in Western populations.      

Plasma lipoprotein levels in vegetarians. The effect of ingestion of fats from dairy products

The influence of dairy foods in the diet on plasma levels of total, low-density lipoprotein, and high-density lipoprotein cholesterol (TC, LDL-C, and HDL-C, respectively) was studied in 75 adult lactovegetarians living in the northeastern United States. Dairy products were the major sources of dietary saturated fat and cholesterol. The plasma TC level was positively correlated with dietary saturated fat and dietary cholesterol, and inversely correlated with the ratio of polyunsaturated to saturated fats in the diet. Correlations between the LDL-C level and the nutrients were similar to those of the TC level. The HDL-C level was not significantly related to any nutrients in the diet. The cholesterol levels of the lactovegetarians were compared with those of strict vegetarians. Lactovegetarians had 24% higher LDL-C levels and 7% higher HDL-C levels than strict vegetarians. Analysis within and among vegetarian populations suggests that ingestion of fatty dairy products raises the LDL-C level on a percentage basis about three times more than it raises the HDL-C level.     

Dietary fish oils containing eicosapentaenoic acid and the prevention of atherosclerosis and thrombosis.

Recent epidemiologic studies have shown that rates of cardiovascular disease are lower in populations such as the Greenland Eskimos than in those that do not eat seafood, even though the levels of dietary fat intake are often similar. Dietary fish oils are rich in eicosapentaenoic acid (EPA), a polyunsaturated fatty acid of the omega-3 series. EPA has been shown to prolong bleeding time and to decrease platelet aggregation and blood viscosity. EPA inhibits the production of prostaglandins from endogenous arachidonic acid, which is associated with the formation of thromboxane A2 and may also dampen cyclo-oxygenase and lipoxygenase metabolites involved in mediating endothelial cell proliferation. Dietary fish oils are now available in the form of EPA-enriched capsules. Short-term trials in humans have shown that EPA significantly reduces the levels of plasma triglycerides and may increase the levels of high-density lipoproteins; however, no consistent effect on serum cholesterol levels has been shown. The results of evaluations of EPA's use in patients with renal disorders, mild hypertension, inflammatory disorders or hyperlipidemia have been promising. On the basis of the epidemiologic and biologic evidence dietary fish oils warrant further study in extensive clinical trials.     

膳食补充单不饱和脂肪酸对2型糖尿病的干预效果

目的 研究膳食补充单不饱和脂肪酸(MUFA)对糖尿病患者的干预效果.方法 上海某社区185例2型糖尿病患者随机分为MUFA干预组(MUFA组,n＝125)和对照组(n＝60).MUFA组食用富含MUFA的茶油3个月,对照组仍食用习惯用油.所有患者分别于干预前和干预后3月检测血糖(空腹血糖和餐后2 h血糖)、空腹胰岛素和血脂水平,并就各项指标进行组内干预前后和组间的比较分析.结果 MUFA组干预3月后的空腹血糖、空腹胰岛素、血清总胆固醇和低密度脂蛋白胆固醇水平均明显低于干预前(P<0.05或P<0.01).组间比较显示,干预前两组各项指标比较差异无统计学意义(P>0.05);干预3月后,MUFA组空腹血糖、血清总胆固醇和低密度脂蛋白胆固醇水平均明显低于对照组(P<0.05).组内干预前后和组间比较显示,甘油三酯和高密度脂蛋白胆固醇水平均无明显变化(P>0.05).结论 膳食补充MUFA对2型糖尿病患者的糖、脂代谢有一定程度的改善作用.     

Associations of dietary fat, regional adiposity, and blood pressure in men

Mediterranean populations have low incidence rates of cardiovascular disease and hypertension that may be due, in part, to dietary factors, particularly a relatively high intake of monounsaturated fat as olive oil. In this study, nutritional components (as grams per 4200 kJ) (1 kcal = 4.2 kJ) from three-day food records were examined in association with resting blood pressure in a cross-sectional survey of 76 sedentary middle-aged American men, aged 30 to 55 years, with resting blood pressures below 160/100 mm Hg. Systolic and diastolic blood pressures correlated significantly and inversely with monounsaturated fat consumption. Polyunsaturated fat consumption also correlated inversely with diastolic blood pressure; however, this relationship became nonsignificant when adjusted for an index of regional adiposity that characterizes the male-type obesity pattern. Detailed analyses of specific fatty acids showed that the correlations with monounsaturates were specific to oleic acid, and the correlation with polyunsaturates was specific to linoleic acid. Multiple regression analysis suggested that 18.2% of the variance in systolic blood pressure and 23.2% of the variance in diastolic blood pressure were related to monounsaturated and polyunsaturated fat consumption and regional adiposity. Thus, increased consumption of monounsaturated fat is related inversely to resting blood pressure, although causality remains to be determined.     

Effect of dietary fatty acids on colon tumorigenesis induced by methyl nitrosourea in rats

To study the effect of dietary fatty acid on the colon tumorigenesis induced by methly nitrosourea in rats,male SD rats were fed five semi-synthetic diets composed of different proportions of beef tallow,soybean oil,alkana oil,corn oil and fish oil for 180 days.The experimental groups were injected with a solution of methyl nitrosourea in phosphate buffer intraperitoneally once a week for six weeks.The control groups were injected with phosphate buffer solution only.The incidence of colon cancer,the avergage volume of the tumors,proliferation cell nuclear antigen,cell kinetics,membrane lipid fluidity,alkaline phophatase activityes and the content of prostaglandin E2 in colon mucosa and the fatty acid of testis pad fat were measured at the end of the experiment.The results showed that the incidence of colon cancer and the average volume of tumors in animals fed with diets composed mainly of beef tallow,soybean oil were significantly higher than those that were fed fish oil.The most effective anticancer diet in our study contained saturated fatty acid,monounsaturated fatty acid and polyunsaturated fatty acid of fish oil in the proportion of 13.9%,16.4%and 68.8% respectively,Inhibition of colon tumorigensis appeared to be related to the regulation of membrane lipid fluidity,and a decrease in the proliferation of cell nuclear antigen in colon cells.In addition,a decrease was noted in the numer of cells in S phase and alkaline phosphatase activity,along with inhibition of arachidonic acid products and a corresponding decrease in the amount of prostaglandin E2.     

The effects of polyunsaturated fat vs monounsaturated fat on plasma lipoproteins

The effect on plasma lipoproteins of exchanging fat type within currently recommended reduced-fat diets was studied in a free-living group of 19 men and 20 women who consumed both a polyunsaturated fat-enriched diet and a monounsaturated fat-enriched diet, each for a 12-week period, with saturated fat and cholesterol held constant. Mean plasma concentrations of low-density lipoprotein cholesterol and low-density lipoprotein total mass (analytic ultracentrifuge), and high-density lipoprotein (HDL) cholesterol and HDL total mass, did not change significantly on exchanging fat type. However, HDL2 cholesterol concentration was 50% higher and HDL3 cholesterol concentration was 7% lower for polyunsaturated compared with monounsaturated fat. Mean total mass of HDL2 was also 23.5% higher and concentration of apolipoprotein B was 5.4% lower on transfer to the polyunsaturated fat diet. Contrary to frequent assertions, we find no advantage with respect to plasma HDL concentrations in using predominantly monounsaturated rather than polyunsaturated fats in subjects who consumed reduced-fat, solid-food diets.     

Serum cholesterol predictive equations in product development

The aim of the study was to incorporate trans fatty acids into predictive equations for serum cholesterol and compare their effects with the effects of the individual saturated fatty acids 12:0, 14:0 and 16:0. We have introduced trans fatty acids from partially hydrogenated soybean oil (TransV) and fish oil (TransF) into previously published equations by constrained regression analysis. Prior knowledge about the signs and ordering of existing regression coefficients were incorporated into the regression modelling by adding lower and upper bounds to the coefficients. Oleic acid (18:1) and polyunsaturated fatty acids (18:2, 18:3) were not sufficiently varied in the studies and the respective regression coefficients therefore set equal to those found by Yu et al. (Am J Clin Nutr 1995;61:1129-39). Stearic acid (18:0) considered to be neutral was not included in the equations. The regression analyses were based on results from four controlled dietary studies with a total of 95 participants and including 10 diets differing in fatty acid composition. The analyses resulted in the following equations where the change in cholesterol is expressed in mmol/L and the change in intake of fatty acids is expressed in E%: Delta Total cholesterol = 0.01 delta(12:0) + 0.12 Delta(14:0) + 0.057 delta(16:0) + 0.039 delta(TransF) + 0.031 delta(TransV)- 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3) and deltaLDL cholesterol = 0.01 delta(12:0) + 0.071 delta(14:0) + 0.047 delta(16:0) + 0.043 delta(TransF) + 0.025 delta(TransV) - 0.0044 delta(18:1) - 0.017 delta(18:2, 18:3). The test set used for validation consisted of 22 data points from seven recently published dietary studies. The equation for total cholesterol showed good prediction ability with a correlation coefficient of 0.981 between observed and predicted values. The equation has been used to reformulate margarines into "trans free" products all with more favourable effects on serum cholesterol than previous products. Also a cholesterol reducing margarine has been produced. When tested against butter in an open clinical trial among subjects with mild hypercholesterolemia the observed cholesterol-lowering effect of this margarine corresponded reasonably well with the predicted (0.77 vs. 0.64 mmol/L). We conclude that the equation has practical applicability and can be used to formulate and nutritionally optimise fat products as well as to evaluate already existing products on the market.     

模拟胃液条件下植物油对亚硝酸盐的作用

在体外模似胃液条件下.六种食用植物油均有效地消除了反应体系中的NaNO_2。消除作用与pH有关.pH3.0时作用最强,pH4.0时次之.植物油中起作用的主要成分可能为亚油酸等不饱和脂肪酸。期望这一结果能为亚硝胺前体分布广泛.而膳食脂摄入过低的食管癌高发地区的膳食脂的补充提供初步依据。     

Effects of Red Palm Oil on Serum Lipids and Plasma Carotenoids Level in Chinese Male Adults

Objective Effects of red palm oil on major plasma carotenoids, tocopherol, retinol and serum lipids were evaluated when used in Chinese diet. Methods Red palm oil group (RPO) composedof 20 male subjects(aged 18-32) and soybean oil group (SBO) composed of 22 male subjects