Polyunsaturated fatty acids may impair blood glucose control in type 2 diabetic patients.

Fifteen patients with Type 2 diabetes were given two diets rich in either saturated fat or polyunsaturated fat in alternate order over two consecutive 3-week periods on a metabolic ward. Both diets contained the same amount of fat, protein, carbohydrates, dietary fibre, and cholesterol. The proportions of saturated, monounsaturated and polyunsaturated fatty acids in the saturated fat diet were 16, 10, and 5%-energy and in the polyunsaturated fat diet (PUFA) 9, 10, and 12%-energy. The PUFA diet contained a high proportion of n-3 fatty acids. Metabolic control improved significantly in both dietary periods, due to both qualitative dietary changes and a negative energy balance. The serum lipoprotein concentrations decreased on both diets but the serum lipids were significantly lower after the PUFA diet (serum triglycerides -20%, p = 0.001; serum cholesterol -5%, p = 0.03; VLDL-triglycerides -29%, p less than 0.001; and VLDL-cholesterol -31%, p = 0.001) than after the saturated fat diet. Average blood glucose concentrations during the third week were significantly higher fasting (+15%, p less than 0.01), and during the day at 1100 h (+18%, p less than 0.001) and 1500 h (+17%, p = 0.002) on PUFA than on the saturated fat diet. Significantly higher blood glucose levels were also recorded with a standard breakfast, while the sum of the insulin values was lower (-19%, p = 0.01). HbA1c did not differ significantly between the two dietary periods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term effects of linoleic-acid-enriched diet on albuminuria and lipid levels in Type 1 (insulin-dependent) diabetic patients with elevated urinary albumin excretion

Summary We conducted a 2-year prospective randomised study to investigate the effects of a linoleic-acid-enriched diet on albuminuria and lipid levels in Type 1 (insulin-dependent) diabetic patients with elevated urinary albumin excretion (overnight urinary albumin excretion rate between 10 and 200 g/min). Thirty-eight patients were randomly assigned to increase dietary polyunsaturated: saturated fatty acids ratio to 1.0 by replacement of saturated fat with linoleic-acid-rich products (n=18, two dropouts, analysis was performed in n=16) or to continue their usual diet (n=20). The total fat and protein content of the diet was unaltered. Clinical characteristics, albuminuria, blood pressure, glomerular filtration rate, metabolic control and dietary composition were similar in the two groups at baseline. In the high linoleic acid diet group, linoleic intake rose from 7±4 to 11±2 energy % and polyunsaturated: saturated fatty acids ratio rose from 0.60±0.28 to 0.96±0.16 (p<0.001 compared to usual diet group). The median increase albuminuria was 58% (95% confidence interval, 13 to 109) during the first year (p<0.02) and 55% (95% confidence interval, 11 to 127) (p<0.01) during the second year. Glomerular filtration rate remained unaltered and filtration fraction tended to rise (p<0.05 compared to usual diet group). In the usual diet group, albuminuria did not significantly increase by 16% (95% confidence interval, -17 to 38) and glomerular filtration rate declined during the second year. Blood pressure tended to rise similarly in both groups. Multiple regression analysis showed an independent effect of the high linoleic acid diet on the progression of albuminuria as well as the lack of decrease in glomerular filtration rate. Low density lipoprotein cholesterol and apolipoprotein B levels decreased in the high linoleic acid diet group (p<0.05). High density lipoprotein cholesterol declined in both groups (p<0.05). It is concluded that a linoleic-acid-enriched diet reduces atherogenic lipoproteins but does not have a beneficial effect on and might even promote renal functional abnormalities in Type 1 diabetic patients with elevated urinary albumin excretion.     

Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU study

Aims/hypothesis. The amount and quality of fat in the diet could be of importance for development of insulin resistance and related metabolic disorders. Our aim was to determine whether a change in dietary fat quality alone could alter insulin action in humans. Methods. The KANWU study included 162 healthy subjects chosen at random to receive a controlled, isoenergetic diet for 3 months containing either a high proportion of saturated (SAFA diet) or monounsaturated (MUFA diet) fatty acids. Within each group there was a second assignment at random to supplements with fish oil (3.6 g n-3 fatty acids/d) or placebo. Results. Insulin sensitivity was significantly impaired on the saturated fatty acid diet (-10 %, p = 0.03) but did not change on the monounsaturated fatty acid diet ( + 2 %, NS) (p = 0.05 for difference between diets). Insulin secretion was not affected. The addition of n-3 fatty acids influenced neither insulin sensitivity nor insulin secretion. The favourable effects of substituting a monounsaturated fatty acid diet for a saturated fatty acid diet on insulin sensitivity were only seen at a total fat intake below median (37E %). Here, insulin sensitivity was 12.5 % lower and 8.8 % higher on the saturated fatty acid diet and monounsaturated fatty acid diet respectively (p = 0.03). Low density lipoprotein cholesterol (LDL) increased on the saturated fatty acid diet ( + 4.1 %, p < 0.01) but decreased on the monounsaturated fatty acid diet (MUFA) (–5.2, p < 0.001), whereas lipoprotein (a) [Lp(a)] increased on a monounsaturated fatty acid diet by 12 % (p < 0.001). Conclusions/interpretation. A change of the proportions of dietary fatty acids, decreasing saturated fatty acid and increasing monounsaturated fatty acid, improves insulin sensitivity but has no effect on insulin secretion. A beneficial impact of the fat quality on insulin sensitivity is not seen in individuals with a high fat intake ( > 37E %). [Diabetologia (2001) 44: 312–319] Received: 21 August 2000 and in revised form: 8 November 2000     

Substituting dietary saturated fat with polyunsaturated fat changes abdominal fat distribution and improves insulin sensitivity

Aims/hypothesis: British dietary recommendations are to decrease total fat intake to less than 30 % of daily energy intake and saturated fat to less than 10 %. In practice, it is difficult for people to make these changes. It may be easier to encourage people to switch from a diet rich in saturated fatty acids to one rich in polyunsaturated fatty acids. Methods: A total of 17 subjects – six people with Type II (non-insulin-dependent) diabetes mellitus, six non-obese and five obese people without diabetes – were randomised to spend two 5-week periods on a diet rich in saturated or in polyunsaturated fatty acids, in a crossover design. At the start of the study and after each dietary period, we assessed abdominal fat distribution using magnetic resonance imaging, insulin sensitivity using hyperinsulinaemic-euglycaemic clamps and fasting lipid parameters. Results: Dietary compliance, assessed by weekly 3-day dietary records and measurement of biochemical markers, was good. Energy and fat intake appeared to be reduced on the diet rich in polyunsaturated fatty acids although body weights did not change. Insulin sensitivity and plasma low density lipoprotein cholesterol concentrations improved with the diet rich in polyunsaturated fatty acids compared with the diet rich in saturated fatty acids. There was also a decrease in abdominal subcutaneous fat area. Conclusion/interpretation: If this result is confirmed in longer-term studies, this dietary manipulation would be more readily achieved by the general population than the current recommendations and could result in considerable improvement in insulin sensitivity, reducing the risk of developing Type II diabetes. [Diabetologia (2002) 45: 369–377] Received: 3 August 2001 and in revised form: 26 November 2001     

Effects of hypocaloric dietary treatment enriched in oleic acid on LDL and HDL subclass distribution in mildly obese women.

OBJECTIVE: To study the effects of a carbohydrate-enriched (HiCarbo) or olive-oil-enriched (HiMUFA) hypocaloric diet on plasma lipoprotein levels and physical properties. DESIGN: A six-month follow-up dietary intervention study with a HiCarbo diet providing 60% of total calories as complex carbohydrates, 15% as proteins and 25% as fats [10% saturated (SFA); 7% monounsaturated (MUFA); 8% polyunsaturated fatty acids (PUFA)]; or a HiMUFA diet with 40% complex carbohydrates, 15% proteins and 45% fats (10% SFA; 27% MUFA; 8% PUFA). SUBJECTS: Twenty consecutive, mildly obese, normolipidemic premenopausal women (11 on HiCarbo and nine on HiMUFA diets) and 14 age- and sex-matched, lean controls. MEASUREMENTS: Body mass index (BMI), waist/hip ratio, plasma lipoproteins, apolipoprotein (apo) AI and B, LDL and HDL density distribution, and phospholipid fatty acid composition at baseline, and after 3 and 6 months on dietary treatment. RESULTS: Body weight progressively decreased during the first 3 months and then it stabilized during the following 3 months (-11% vs. baseline in both groups; P < 0.01). LDL-Cholesterol decreased significantly in both groups. HDL-Cholesterol increased significantly in the HiMUFA group, whereas a decreased level was observed in the HiCarbo group. At baseline the obese women had higher very low density lipoprotein (VLDL) and dense LDL-Cholesterol, and lower HDL2 cholesterol levels than the controls; these abnormalities persisted in the HiCarbo diet, whilst a significant decrease in the dense LDL associated with an increase in the HDL2 cholesterol was seen in the HiMUFA diet. HDL3 was not affected by either diet. The LDL/HDL-Cholesterol ratio was not affected by the HiCarbo diet, whilst it was significantly reduced after 6 months of HiMUFA diet as compared with baseline. Apo AI increased in the HiMUFA group, and decreased in the HiCarbo group. CONCLUSIONS: Both diets were effective in decreasing body weight. At steady weight conditions, only the HiMUFA diet improved LDL and HDL subclass distribution abnormalities present in mildly obese normolipidemic women.     

Comparison of the Effects on the Diurnal Blood Pressure,Glucose, and Lipid Levels of a Diet Rich in Monounsaturated Fatty Acids With a Diet Rich in Polyunsaturated Fatty Acids in Type 2 Diabetic Subjects

The influence on blood pressure, glucose metabolism, and lipid levels of an exchange of polyunsaturated fatty acids with monounsaturated fatty acids in the diet was compared in 16 Type 2 diabetic outpatients. In a cross-over study design the patients were randomly assigned to 3 weeks treatments with a diet containing 30% energy as monounsaturated fatty acids, or an isoenergetic diet with 30% energy as polyunsaturated fatty acids. The contents of total fat, satuarated fatty acids, cholesterol, and fibre were similar in the two diets. On the last days of the two diet periods, 24-h ambulatory blood pressure was measured and the responses of glucose, hormones, and lipids to a carbohydrate rich test meal were measured. As compared with the polyunsaturated fatty acids diet, the monounsaturated fatty acids diet reduced 24-h systolic (129 ± 11 vs 124 ± 8 mmHg (mean ± SD), p = 0.02) and diastolic blood pressure (76 ± 11 vs 73 ± 8 mmHg, p = 0.02). The two diets had similar, beneficial effects on glycaemic control, and cholesterol and lipoprotein concentrations. A diet rich in monounsaturated fatty acids has beneficial effects on the blood pressure, while similar effects on glucose and lipid levels are observed in normotensive Type 2 diabetic subjects.     

Diet and risk of Type II diabetes: the role of types of fat and carbohydrate

Although diet and nutrition are widely believed to play an important part in the development of Type II (non-insulin-dependent) diabetes mellitus, specific dietary factors have not been clearly defined. Much controversy exists about the relations between the amount and types of dietary fat and carbohydrate and the risk of diabetes. In this article, we review in detail the current evidence regarding the associations between different types of fats and carbohydrates and insulin resistance and Type II diabetes. Our findings indicate that a higher intake of polyunsaturated fat and possibly long-chain n-3 fatty acids could be beneficial, whereas a higher intake of saturated fat and trans-fat could adversely affect glucose metabolism and insulin resistance. In dietary practice, exchanging nonhydrogenated polyunsaturated fat for saturated and trans-fatty acids could appreciably reduce risk of Type II diabetes. In addition, a low-glycaemic index diet with a higher amount of fiber and minimally processed whole grain products reduces glycaemic and insulinaemic responses and lowers the risk of Type II diabetes. Dietary recommendations to prevent Type II diabetes should focus more on the quality of fat and carbohydrate in the diet than quantity alone, in addition to balancing total energy intake with expenditure to avoid overweight and obesity. [Diabetologia (2001) 44: 805–817]     

单不饱和脂肪酸膳食通过缓解氧化应激改善糖耐量正常人群的胰岛素敏感性

20例健康受试者分别接受单不饱和脂肪酸饮食、多不饱和脂肪酸饮食、饱和脂肪酸饮食3d,单不饱和脂肪酸可以改善机体的氧化应激状态,从而改善胰岛素敏感性.     

Mediterranean and low-fat diets improve endothelial function in hypercholesterolemic men.

BACKGROUND: The regulatory function of the endothelium is altered in hypercholesterolemia, and the subsequent endothelial dysfunction plays a central role in the development of atherosclerosis. OBJECTIVE: To determine whether endothelial function in hypercholesterolemic patients is affected by replacing a saturated fat-enriched diet with a low-fat, low-saturated fat diet (the U.S. National Cholesterol Education Program stage 1 [NCEP-1] diet) or a diet rich in monounsaturated fat (such as that common in Mediterranean countries). DESIGN: Intervention dietary study with a baseline phase and two randomized crossover dietary periods. SETTING: Hospital Universitario Reina Sofía, Córdoba, Spain. PATIENTS: 22 hypercholesterolemic men. INTERVENTION: Patients followed a diet high in saturated fat, then were assigned in a crossover design to the NCEP-1 diet or a Mediterranean diet. Each dietary period lasted 28 days. MEASUREMENTS: Plasma P-selectin levels, lipid concentrations, and endothelial function. RESULTS: Compared with the saturated fat diet, flow-mediated dilatation increased during the Mediterranean diet but not during the NCEP-1 diet. In addition, levels of plasma cholesterol, low-density lipoprotein cholesterol, apolipoprotein B, and P-selectin decreased during the NCEP-1 and Mediterranean diets. CONCLUSION: In hypercholesterolemic men, diets low in fat (especially saturated fat) and diets rich in monounsaturated fats improve endothelial function.     

Maternal diet rich in saturated fats has deleterious effects on plasma lipids of mice

BACKGROUND AND OBJECTIVES: High dietary fat intake has been reported to cause an alteration in lipid metabolism that is associated with an increased risk of cardiovascular disease. In the present study, an animal model was used to evaluate the effects of feeding diets rich in different fatty acids to mothers during pregnancy and lactation, and the effects of the maternal diet on parameters of lipid metabolism in adult offspring. The interaction between the offspring's own diet and the programming due to the maternal diet was also evaluated. METHODS: Female C57BL/6 mice were fed a high-fat diet (20% fat [weight to weight]) rich in either saturated fatty acids (SFA) or polyunsaturated fatty acids (PUFA) for two weeks before mating, during pregnancy and until weaning. The offspring were divided into two groups; each group was fed a high-fat diet enriched in either SFA or PUFA for eight weeks after weaning. The groups were designated as SFA/SFA (diet of the mother/diet of the offspring), SFA/PUFA, PUFA/PUFA and PUFA/SFA. Blood and tissues were collected at the end of the eight-week feeding period after an overnight fast. RESULTS: The plasma total cholesterol and low density lipoprotein cholesterol concentrations were significantly higher in the SFA/SFA group than in all other groups, whereas the PUFA/PUFA group had the lowest total cholesterol and low density lipoprotein cholesterol concentrations. Plasma high density lipoprotein cholesterol concentrations were significantly higher in the PUFA/SFA group than in the PUFA/PUFA and SFA/PUFA groups, whereas plasma triglyceride concentrations were not different among the groups. CONCLUSIONS: The data suggest that high maternal dietary fat intake during pregnancy affects lipid metabolism in the adult offspring. However, it appears that the offspring's own diet is also important in maintaining the regulation of lipid metabolism.     

The effect of dietary fat content and composition on adipocyte lipids in normal and diabetic states

Cellular insulin resistance is a common feature of the diabetic and obese state. To determine the effect of dietary fat and the insulin resistant state of diabetes on adipose tissue composition, control and streptozotocin-induced diabetic rats were fed four diets differing in fat content (10 percent w/w or 20% w/w) and polyunsaturated to saturated fatty acid (P/S) ratios (0.2 or 2.0) for 6 weeks. At 3 weeks diabetes was induced in half the animals in each diet group. Increasing the fat content and P/S ratio of the diet increased the content of polyunsaturated fatty acids and decreased the contents of monounsaturated and omega-3 fatty acids. The higher level of C-18:2(6) and the lower levels of C20:4(6) and monounsaturated fatty acids observed in diabetic animals is consistent with altered desaturase enzyme activity. Diet and diabetes induced compositional changes in essential and non-essential fatty acids in the adipose tissue may alter the total body pools of available fatty acids for the synthesis of other lipids such as phospholipids.     

Increased cholesterylester transfer activity in complicated Type 1 (insulin-dependent) diabetes mellitus — its relationship with serum lipids

Summary In Type 1 (insulin-dependent) diabetes mellitus, macrovascular complications and the increased risk for cardiovascular disease in patients with microvascular complications may be related to alterations in plasma cholesterylester transfer. The activity of cholesterylester transfer protein, which mediates cholesterylester transfer between lipoproteins and lipoprotein lipid levels, was assessed in 7 normolipidaemic control subjects, 7 Type 1 diabetic control subjects without complications, 11 Type 1 diabetic patients with microvascular complications (retinopathy, incipient nephropathy) and in 7 Type 1 diabetic patients with macrovascular atherosclerotic lesions.The cholesterylester transfer activity was 30% higher in the diabetic groups with macrovascular and microvascular lesions than in the 2 control groups. Very low + low density lipoprotein cholesterol was higher in the 3 diabetic groups than in the non-diabetic control group. High density lipoprotein cholesterol was not different. The cholesterylester transfer activity was correlated positively with HbA1, urinary albumin excretion rate, serum cholesterol, very low + low density lipoprotein cholesterol and apolipoprotein B. The high density lipoprotein over very low + low density lipoprotein cholesterylester molar ratio was lower in the diabetic groups with micro- and macrovascular complications. A role for cholesterylester transfer activity in the lipoprotein abnormalities found in complicated Type 1 diabetes is suggested. A high cholesterylester transfer activity might be indicative of mechanisms which promote atherogenesis.     

A reduction in dietary saturated fat decreases body fat content in overweight, hypercholesterolemic males

BACKGROUND AND AIM: The effect of the quality of dietary fat on body composition is unknown. Our objective was to determine whether body composition is modified by the isocaloric substitution of a diet rich in saturated fat by a diet high in monounsaturated fat (Mediterranean diet) or a carbohydrate-rich diet in overweight subjects with hypercholesterolemia. METHODS AND RESULTS: The study involved 34 hypercholesterolemic males aged 18-63 years with a body mass index (BMI) of 28.2 (2.6), all of whom consumed a diet rich in saturated fat (SAT) for 28 days. They were then randomly divided into two groups of 17 subjects and underwent two dietary periods of 28 days each in a crossover design: a Mediterranean diet high in monounsaturated fat (MONO) and a carbohydrate-rich diet (CHO). The order of the diets was different for the two group. The CHO diet contained 57% CHO and 28% total fat (< 10% saturated fat, 12% monounsaturated fat and 6% polyunsaturated fat); the Mediterranean diet contained 47% CHO and 38% fat (< 10% saturated fat, 22% monounsaturated fat--75% of which was provided by olive oil- and 6% polyunsaturated fat). The variables measured at the end of each dietary intervention period were: 1) body composition by means of bioelectrical impedance; 2) plasma lipoproteins using enzymatic techniques; and 3) fatty acids in cholesterol esters by means of gas chromatography. BMI and the waist/hip ratio remained the same during the three dietary periods. A decrease in fat was observed when changing from a saturated fat diet (23.3 (6.3) kg) to a Mediterranean diet (20.8 (7.2) kg) (p < 0.05), or a carbohydrate-rich diet (20.6 (6.7) kg) (p < 0.05). Lean mass increased when changing from a SAT diet (58.4 (7.0) kg) to a CHO diet (60.2 (7.0) kg) (p < 0.05). CONCLUSION: The isocaloric substitution of a saturated fat-rich diet by a Mediterranean or carbohydrate-rich diet decreases total body fat in hypercholesterolemic males.     

The fatty acid composition of chylomicron remnants influences their propensity to oxidate

BACKGROUND AND AIM: Although the replacement of saturated with unsaturated dietary fat has been advocated as a means of reducing the risk of cardiovascular disease, diets high in polyunsaturated fatty acids (PUFAs) may increase lipid peroxidation, thus contributing to the pathogenesis of atherosclerosis. As the susceptibility of individual fatty acids to oxidation directly depends on their degree of unsaturation, and the oxidative modification of lipoproteins may be an important determinant of atherogenesis, the aim of this study was to evaluate the susceptibility to auto-oxidation and copper-mediated oxidation of chylomicron remnants (CMRs) enriched in n-3 or n-6 PUFA. METHODS AND RESULTS: The remnants were prepared in vitro from chylomicrons obtained from rats given an oral dose of fish or corn oil, using rat plasma containing lipoprotein lipase. Their propensity to oxidate and the extent of the oxidation were estimated by measuring the formation of conjugated dienes and the detrimental products of lipid peroxidation. The results showed that: 1) the corn oil CMRs contained a relatively high proportion of n-6 PUFA (mainly linoleic acid), whereas the fish oil CMRs contained more n-3 PUFA, mainly eicosapentanoic and docosahexaenoic acids; 2) n-3-rich CMRs have a significantly lower propensity to oxidate than n-6-rich CMRs despite their 50% lower alpha-tocopherol content and 40% higher unsaturation index. CONCLUSION: Our data indicate that the precise allocation of n-3 PUFA within the lipid core of CMRs may play a pivotal role in lowering the susceptibility to oxidation of fish CMRs by overcoming the effects of unfavourable alpha-tocopherol concentration. Eating n-3 rather than n-6 PUFAs seems to make CMRs more resistant against free radical attack, which may contribute to attenuating their potential atherogenic properties.     

Diet, lipids, and coronary heart disease

This review has highlighted some of the experimental studies in animals and humans that have shown an important link between dietary change and atherosclerosis. This relationship was further supported by population studies showing a key role for saturated fat intake in the determination of serum cholesterol level and the prediction of CHD. Recent data linking dietary cholesterol independent of serum cholesterol level to the prediction of CHD were discussed as well. Various components of the diet and their effects on lipid and lipoproteins were reviewed. The chief factors in the diet which raise cholesterol and low-density lipoprotein cholesterol (LDL-c) are dietary cholesterol, saturated fat, and excess calories leading to obesity. Dietary factors useful in lowering cholesterol and low-density lipoprotein cholesterol include monounsaturated fats, polyunsaturated fats, and dietary fiber, which can be substituted for saturated fats. The usefulness of a special class of polyunsaturated oil, the omega-3 fatty acids, in both lowering triglyceride levels and preventing thrombosis was also discussed. Although alcohol raises the HDL-c level, it is not clear that its use offers protection against CHD, and its risks clearly outweigh its advantages in this regard. Regular aerobic exercise is recommended as a healthier alternative to raising high-density lipoprotein cholesterol. Also discussed was postprandial lipemia, which may prove to be another indicator of risk of CHD. Finally, the recent NCEP dietary guidelines were discussed along with practical suggestions as to their implementation.     

Comparison of a high-carbohydrate and a high-monounsaturated fat, olive oil-rich diet on the susceptibility of LDL to oxidative modification in subjects with Type 2 diabetes mellitus.

AIMS: To compare the effects of a high-carbohydrate (CHO) diet and a high-monounsaturated fatty acid (MUFA) diet on LDL oxidative resistance in free-living individuals with Type 2 diabetes mellitus. METHODS: Twenty-two men and women out-patients with Type 2 diabetes, with mean age 61 years and in fair metabolic control (HbA1c<8.0%), were enrolled at a university hospital lipid clinic in a randomized, crossover feeding trial comparing two isocaloric diets for 6 weeks each: CHO (fat, 28% energy) and MUFA (fat, 40% energy) based on virgin olive oil. Outcome measurements were changes in LDL susceptibility to oxidation, body weight, glycaemic control, and lipoprotein profiles. RESULTS: Planned and observed diets were well matched. Participants preferred the MUFA diet over the CHO diet. The lag time of conjugated diene formation during Cu2+-induced LDL oxidation was similar after the CHO and MUFA diets (36.4 +/- 12.2 min and 36.0 +/- 13.7 min, respectively). Body weight, glycaemic control, total triglycerides, and total, LDL- and HDL-cholesterol levels also were similar after the two diets. Compared with the CHO diet, the MUFA diet lowered VLDL-cholesterol by 35% (P=0.023) and VLDL triglyceride by 16% (P=0.016). CONCLUSIONS: Natural food-based high-CHO and high-MUFA diets have similar effects on LDL oxidative resistance and metabolic control in subjects with Type 2 diabetes. A MUFA diet is a good alternative to high-CHO diets for nutrition therapy of diabetes because it also has a beneficial effect on the lipid profile and superior patient acceptance.     

Protective effect of dietary monounsaturated fat on arteriosclerosis: beyond cholesterol

The consumption of diets enriched in monounsaturated fat has been related to a lower rate of coronary heart disease. It is well known that this dietary model decreases LDL-cholesterol plasma levels when replacing a saturated fat enriched diet. For this reason, a high monounsaturated fat diet is now being advocated to prevent cardiovascular disease, especially in Mediterranean countries. However, some expert panels-the Joint Task Force of European and other Societies on Coronary Prevention and the International Task Force for Prevention of Coronary Heart Disease-recommend replacing dietary saturated fat by complex carbohydrates, limiting the intake of total fat to <30% of the energy and monounsaturated fat to no more than 10-15% of total calories, reaching a similar effect on LDL-cholesterol plasma levels to a high monounsaturated fat diet. The most appropriate nutritional model to prevent arteriosclerosis should be supported by research into other biological effects of both diets. Therefore, it is interesting to review the non-lipid effect of monounsaturated fat, starting with its influence on other cardiovascular risk factors, such as carbohydrate metabolism and blood pressure. Moreover, substantial evidence of the effect of dietary monounsaturated fat on a wide range of healthy benefits beyond cholesterol, which have been investigated in recent years, such as lipoprotein oxidation, coagulation, fibrinolysis and endothelium, will be discussed. Furthermore, many observational epidemiological studies suggest that a high intake of monounsaturated fat is associated with reduced coronary risk and this will be analyzed in accordance with the clinical evidence to discuss the best dietary model to prevent coronary artery disease.     

Lipid metabolism in pregnancy and its consequences in the fetus and newborn

During early pregnancy there is an increase in body fat accumulation, associated with both hyperphagia and increased lipogenesis. During late pregnancy there is an accelerated breakdown of fat depots, which plays a key role in fetal development. Besides using placental transferred fatty acids, the fetus benefits from two other products: glycerol and ketone bodies. Although glycerol crosses the placenta in small proportions, it is a preferential substrate for maternal gluconeogenesis, and maternal glucose is quantitatively the main substrate crossing the placenta. Enhanced ketogenesis under fasting conditions and the easy transfer of ketones to the fetus allow maternal ketone bodies to reach the fetus, where they can be used as fuels for oxidative metabolism as well as lipogenic substrates. Although maternal cholesterol is an important source of cholesterol for the fetus during early gestation, its importance becomes minimal during late pregnancy, owing to the high capacity of fetal tissues to synthesize cholesterol. Maternal hypertriglyceridemia is a characteristic feature during pregnancy and corresponds to an accumulation of triglycerides not only in very low-density lipoprotein but also in low- and high-density lipoprotein. Although triglycerides do not cross the placental barrier, the presence of lipoprotein receptors in the placenta, together with lipoprotein lipase, phospholipase A₂, and intracellular lipase activities, allows the release to the fetus of polyunsaturated fatty acids transported as triglycerides in maternal plasma lipoproteins. Normal fetal development needs the availability of both essential fatty acids and long chain polyunsaturated fatty acids, and the nutritional status of the mother during gestation has been related to fetal growth. However, excessive intake of certain long chain fatty acids may cause both declines in arachidonic acid and enhanced lipid peroxidation, reducing antioxidant capacity.     

Urinary albumin excretion rate and 24-h ambulatory blood pressure in NIDDM with microalbuminuria: effects of a monounsaturated-enriched diet

Summary Previous studies have shown that unsaturated fat-enriched diets may have a beneficial effect on blood pressure in non-insulin-dependent diabetic (NIDDM) patients, whereas little is known about the effects on albuminuria. In a 3-week cross-over design we compared the effects of a currently recommended high-carbohydrate diet (50% carbohydrate, 30% fat [10% monounsaturated fat]) vs a diet rich in monounsaturated fat (30% carbohydrate, 50% fat [30% monounsaturated fat]) on urinary albumin excretion rate, 24-h ambulatory blood pressure and metabolic control in ten NIDDM patients with persistent microalbuminuria. The 24-h ambulatory blood pressure was similar before and after both the high-carbohydrate diet (mean±SD: 145/78±25/10 vs 143/79±19/10 mmHg (NS) and the monounsaturated fat diet: 140/78±16/8 vs 143/79±15/8 mmHg (NS). No changes were observed in day or night-time blood pressures. Urinary albumin excretion rate was unaffected after 3 weeks' treatment by the diets: from (geometric mean ×/÷ tolerance factor) 32.4×/÷2.1 to 36.0×/÷1.9 g/min (NS) vs from 34.2×/÷1.9 to 32.1×/÷2.1 g/min (NS). Fasting plasma glucose, serum fructosamine and HbA_1c as well as lipid and lipoprotein concentrations were stable during both diets. Compared to the high-carbohydrate diet a reduction in the LDL/HDL cholesterol ratio was observed during the monounsaturated fat diet (p<0.03). In conclusion, compared to a high-carbohydrate diet, 3 weeks' treatment with a monounsaturated fat diet did not affect the levels of 24-h ambulatory blood pressure or albuminuria in microalbuminuric NIDDM patients. Moreover, glycaemic control and lipoprotein levels were unchanged, although a potential beneficial effect on the LDL/HDL-cholesterol ratio was noted. Monounsaturated fat represents an alternative in the diets of NIDDM patients especially when caloric intake is not a concern.Abbreviations UAE Urinary albumin excretion rate - NIDDM non-insulin-dependent diabetes mellitus - MUFA monounsaturated fatty acids - PUFA polyunsaturated fatty acids - ANOVA analysis of variance - CHO carbohydrate - CI confidence interval     

Is a low fat diet the optimal way to cut energy intake over the long-term in overweight people?

Successful weight loss depends on maintaining a sustained negative energy balance. This can be achieved on diets with a normal (40% energy) fat content as well as on low fat diets. Using a 'modified fat' (MF) diet enriched with monounsaturated fat (MUFA), body weight may be lost either by calorie counting, or by allowing ad libitum food intake with careful food selection. In the latter approach high energy, high MUFA foods (predominantly olive oil, but also may include nuts and avocado) should contribute no more than 20% total energy to the diet, and other foods should be selected to minimise meal energy density. This can be achieved simply by the consumption of a wide variety of vegetables and whole grain cereal foods. It is also important to restrict foods high in saturated fat and to encourage regular exercise. Such a 'modified fat' low energy diet designed for weight loss should also contribute numerous health benefits in relation to improved metabolic control in Type 2 diabetes and reduced cardiovascular disease risk (as the diet is not only rich in MUFA but also in a range of dietary antioxidants and other bio-active phytochemicals).