Serum lipid and apolipoprotein concentrations in healthy men on diets enriched in either canola oil or safflower oil

This randomized, blind study measured changes in serum lipid and apolipoprotein concentrations in 16 men consuming 39 +/- 1% of energy (en%) as fat either from safflower- or canola-oil-based diets for 8 wk. Initially, the men were stabilized for 3 wk on a typical American (baseline) diet. Compared with baseline, the vegetable-oil-based diets reduced serum total cholesterol 9-15% (P less than 0.002), low-density-lipoprotein (LDL)-cholesterol 12-20% (P less than 0.002), and apolipoprotein B-100 21-24% (P less than 0.001). There were no significant changes from baseline to the end of the study in serum triglycerides, total high-density-lipoprotein (HDL) cholesterol, HDL3 cholesterol, HDL2 cholesterol, or apolipoprotein A-I. These data suggest that even if total fat intake remains at 39-40 en%, many men show lowered LDL cholesterol if saturated fatty acid intake is minimized and that diets high in polyunsaturated fatty acids do not necessarily lower HDL-cholesterol concentrations.     

Effect of dietary monounsaturated fatty acids on plasma lipoproteins and apolipoproteins in women.

To determine the effects of dietary fat saturation on plasma lipoproteins, we studied 21 free-living normolipidemic women (13 pre- and 8 postmenopausal) on three consecutive diet periods. During the first 4 wk they consumed a saturated diet rich in palm oil and butter [19% saturated fatty acids (S), 14% monounsaturated fatty acids (M), and 3.5% polyunsaturated fatty acids (P)], followed by 6 wk of a monounsaturated diet rich in olive oil (11% S, 22% M, and 3.6% P), and 6 wk of a polyunsaturated diet rich in sunflower oil (10.7% S, 12.5% M, and 12.8% P). Compared with the diet rich in saturated fatty acids, both diets rich in unsaturated fatty acids had similar lowering effects on total and low-density-lipoprotein cholesterol. High-density lipoprotein cholesterol and apolipoprotein A-I were higher in the monounsaturated-rich period than in the polyunsaturated-rich (10.5% and 12.7% respectively, P less than 0.001) and the saturated-rich period (5.3%, and 7.9%, respectively, P less than 0.05). These effects were independent of menopause status. Our data show that at this level of fat intake (36% as calories), a monounsaturated-rich diet results in a less atherogenic lipid profile than either polyunsaturated- or saturated-rich diets.     

Fatty acid saturation of the diet and plasma lipid concentrations, lipoprotein particle concentrations, and cholesterol efflux capacity

BACKGROUND: The fatty acid content and saturation degree of the diet can modulate HDL composition and cholesterol efflux. OBJECTIVE: We studied the modifications in plasma lipoprotein particles and serum capacity to stimulate cholesterol efflux induced by different fatty acids. DESIGN: Seventeen women and 24 men followed in the same sequence 4 diets containing 35% of total energy as fat. The saturated fat diet contained 17% palm oil; the monounsaturated fat diet, 20.9% olive oil; the n-6 polyunsaturated fat diet, 12.5% sunflower oil; and the n-3 polyunsaturated fat diet, sunflower oil supplemented with 4-4.5 g fish oil/d. Each phase lasted 4-5 wk. RESULTS: In both sexes, apolipoprotein (apo) A-I concentrations were significantly lower with unsaturated fat diets than with the saturated fat diet, but concentrations of lipoproteins containing only apo A-I (Lp A-I) were lower only in the men. Concentrations of lipoproteins containing both apo A-I and apo A-II (Lp A-I:A-II) were lower with both polyunsaturated fat diets in the women but significantly higher in the men. Lp E concentrations were significantly higher with the 2 polyunsaturated fat diets. Lp E non-B particle concentrations were not modified in the men but were significantly higher in the women in both polyunsaturated fat phases. Lp C-III concentrations were higher with the saturated fat diet only in the men. The serum samples taken after the n-3 polyunsaturated fat phase were the most efficient for extracting cellular cholesterol in both sexes. CONCLUSIONS: The monounsaturated and polyunsaturated fat diets were healthier, producing a better lipid profile. The n-3 polyunsaturated fat diet increased the capacity of serum to promote the efflux of cholesterol from cells in culture.     

Cholesterol-lowering effect of a low-fat diet containing lean beef is reversed by the addition of beef fat

The aim of this study was to differentiate between lean beef and beef fat as risk factors for elevated plasma cholesterol concentrations. Ten healthy weight-stable subjects (five men, five women) participated. Energy intake was kept constant over the 5-wk study. Total cholesterol concentrations fell significantly within 1 wk of commencing the very-low fat (9%) energy from fat) lean-beef (500 g/d) diet (5.91 +/- 0.47 to 4.72 +/- 0.42 mmol/L, p less than 0.001) and rose as beef drippings were added in a stepwise manner in weeks 4 and 5 (5.45 +/- 0.56 mmol/L in week 5). The changes in total cholesterol concentrations were due almost entirely to changes in the concentration of low-density lipoprotein cholesterol levels. These results indicate that it is the beef fat, not lean beef itself, that is associated with elevations in cholesterol concentrations and that lean beef can be included in cholesterol-lowering diets provided it is free of all visible fat and the saturated fatty acid content of the diet is low.     

The effect of daily consumption of coconut fat and soya-bean fat on plasma lipids and lipoproteins of young normolipidaemic men

The present paper reports the influence on plasma lipids of isoenergetic diets containing 30% of energy as fat, with a polyunsaturated: saturated fat ratio of 4.00 or 0.25, consumed for 8 weeks by twenty-five young normolipidaemic males. Approximately 70% of the fat energy was provided by the test fats: soya-bean fat and coconut fat. During the soya-bean-fat-eating period the total plasma cholesterol level fell significantly compared with baseline values (P less than 0.001) and during the coconut-fat-eating phase total plasma cholesterol level increased significantly compared with the soya-bean-eating period (P less than 0.001). On the soya-bean-fat diet, high-density-lipoprotein (HDL)-cholesterol decreased by 15% (range 6-35%) and plasma triacylglycerols decreased by 25% (range 13-37%). Results of the present study show that even when the proportion of total fat in the diet is low, a high intake of linoleic acid lowers both total plasma cholesterol and HDL-cholesterol, while a high intake of saturated fat elevates both these lipid fractions. Application of regression formulas to the present findings indicates that short-chain saturated fatty acids have a neutral effect on serum cholesterol.     

Comparative effects of a recommended lipid-lowering diet vs a diet rich in monounsaturated fatty acids on serum lipid profiles in healthy young adults.

This crossover study investigated the effects of two fat-reduced diets, one rich in monounsaturated fatty acids (MUFAs), the other rich in polyunsaturated fatty acids (PUFAs), on serum lipid profiles in 38 healthy young adults initially on a typical western diet. After being randomly assigned to two groups, the subjects received the MUFA or PUFA diet for 3-wk and then the other diet for 3 wk. Both test diets led to significant reductions in serum cholesterol, LDL cholesterol, and HDL cholesterol (P less than 0.001). Both reduced apolipoprotein B (P less than 0.001) and apolipoprotein A-I concentrations (P less than 0.01 for the MUFA, P less than 0.001 for the PUFA diet). Apolipoprotein A-I was significantly higher on the MUFA than on the PUFA diet. The ratio of apolipoprotein A-I to B significantly increased on both diets. Thus, a low-fat, MUFA-rich diet is as effective as a low-fat, PUFA-rich diet in lowering total and LDL cholesterol, but both also lowered HDL cholesterol concentrations. The MUFA-rich diet may be more advantageous than the PUFA-rich one because it does not lower apolipoprotein A-I concentrations as much as the PUFA-rich diet.     

Individual variability in cardiovascular disease risk factor responses to low-fat and low-saturated-fat diets in men: body mass index, adiposity, and insulin resistance predict changes in LDL cholesterol

BACKGROUND: Although reductions in total and saturated fat consumption are recommended to reduce the risk of cardiovascular disease, individual variability in plasma lipid responses exists. OBJECTIVE: Our aim was to determine the effect of adiposity and insulin resistance on the lipoprotein response to diets lower in total and saturated fat than the average American diet (AAD). DESIGN: A randomized, double-blind, 3-period crossover controlled feeding design was used to examine the effects on plasma lipids of 3 diets that differed in total fat: the AAD [designed to contain 38% fat and 14% saturated fatty acids (SFAs)], the Step I diet (30% fat with 9% SFAs), and the Step II diet (25% fat with 6% SFAs). The diets were fed for 6 wk each to 86 free-living, healthy men aged 22-64 y at levels designed to maintain weight. RESULTS: Compared with the AAD, the Step I and Step II diets lowered LDL cholesterol by 6.8% and 11.7%, lowered HDL cholesterol by 7.5% and 11.2%, and raised triacylglycerols by 14.3% and 16.2%, respectively. The Step II diet response showed significant positive correlations between changes in both LDL cholesterol and the ratio of total to HDL cholesterol and baseline percentage body fat, body mass index, and insulin. These associations were largely due to smaller reductions in LDL cholesterol with increasing percentage body fat, body mass index, or insulin concentrations. Subdivision of the study population showed that the participants in the upper one-half of fasting insulin concentrations averaged only 57% of the reduction in LDL cholesterol with the Step II diet of the participants in the lower half. CONCLUSION: Persons who are insulin resistant respond less favorably to Step II diets than do those who are insulin sensitive.     

Rice bran oil, not fiber, lowers cholesterol in humans

BACKGROUND: The cholesterol-lowering abilities of rice bran's fiber and oil apart from its fatty acid composition remain unclear. OBJECTIVE: The objective of the study was to assess the effects of defatted rice bran and rice bran oil in an average American diet on blood lipids in moderately hypercholesterolemic persons. DESIGN: Study 1 used a parallel-arm design. Twenty-six healthy volunteers consumed a diet with 13-22 g dietary fiber/d for 3 wk, and then 13 of the volunteers were switched to a diet with defatted rice bran to double the fiber intake for 5 wk. Study 2 was a randomized, crossover, 10-wk feeding study performed in 14 volunteers who consumed a diet with rice bran oil (1/3 of the total dietary fat) substituted for an oil blend that had a fatty acid composition similar to that of the rice bran oil. Serum lipids and factor VII were measured in both studies. RESULTS: Defatted rice bran did not lower lipid concentrations. In study 2, total cholesterol was significantly lower with consumption of the diet containing rice bran oil than with consumption of the control diet. Moreover, with consumption of the rice bran oil diet, LDL cholesterol decreased by 7% (P < 0.0004), whereas HDL cholesterol was unchanged. CONCLUSIONS: Rice bran oil, not fiber, lowers cholesterol in healthy, moderately hypercholesterolemic adults. There were no substantial differences in the fatty acid composition of the diets; therefore, the reduction of cholesterol was due to other components present in the rice bran oil, such as unsaponifiable compounds.     

Separate effects of reduced carbohydrate intake and weight loss on atherogenic dyslipidemia

BACKGROUND: Low-carbohydrate diets have been used to manage obesity and its metabolic consequences. OBJECTIVE: The objective was to study the effects of moderate carbohydrate restriction on atherogenic dyslipidemia before and after weight loss and in conjunction with a low or high dietary saturated fat intake. DESIGN: After 1 wk of consuming a basal diet, 178 men with a mean body mass index (in kg/m(2)) of 29.2 +/- 2.0 were randomly assigned to consume diets with carbohydrate contents of 54% (basal diet), 39%, or 26% of energy and with a low saturated fat content (7-9% of energy); a fourth group consumed a diet with 26% of energy as carbohydrate and 15% as saturated fat. After 3 wk, the mean weight loss (5.12 +/- 1.83 kg) was induced in all diet groups by a reduction of approximately 1000 kcal/d for 5 wk followed by 4 wk of weight stabilization. RESULTS: The 26%-carbohydrate, low-saturated-fat diet reduced triacylglycerol, apolipoprotein B, small LDL mass, and total:HDL cholesterol and increased LDL peak diameter. These changes were significantly different from those with the 54%-carbohydrate diet. After subsequent weight loss, the changes in all these variables were significantly greater and the reduction in LDL cholesterol was significantly greater with the 54%-carbohydrate diet than with the 26%-carbohydrate diet. With the 26%-carbohydrate diet, lipoprotein changes with the higher saturated fat intakes were not significantly different from those with the lower saturated fat intakes, except for LDL cholesterol, which decreased less with the higher saturated fat intake because of an increase in mass of large LDL. CONCLUSIONS: Moderate carbohydrate restriction and weight loss provide equivalent but nonadditive approaches to improving atherogenic dyslipidemia. Moreover, beneficial lipid changes resulting from a reduced carbohydrate intake were not significant after weight loss.     

Effects of medium-chain fatty acids and oleic acid on blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities

BACKGROUND: Dietary medium-chain fatty acids (MCFAs) are of nutritional interest because they are more easily absorbed from dietary medium-chain triacylglycerols (MCTs) than are long-chain fatty acids from, for example, vegetable oils. It has generally been claimed that MCFAs do not increase plasma cholesterol, although this claim is poorly documented. OBJECTIVE: We compared the effects of a diet rich in either MCFAs or oleic acid on fasting blood lipids, lipoproteins, glucose, insulin, and lipid transfer protein activities in healthy men. DESIGN: In a study with a double-blind, randomized, crossover design, 17 healthy young men replaced part of their habitual dietary fat intake with 70 g MCTs (66% 8:0 and 34% 10:0) or high-oleic sunflower oil (89.4% 18:1). Each intervention period lasted 21 d, and the 2 periods were separated by a washout period of 2 wk. Blood samples were taken before and after the intervention periods. RESULTS: Compared with the intake of high-oleic sunflower oil, MCT intake resulted in 11% higher plasma total cholesterol (P = 0.0005), 12% higher LDL cholesterol (P = 0.0001), 32% higher VLDL cholesterol (P = 0.080), a 12% higher ratio of LDL to HDL cholesterol (P = 0.002), 22% higher plasma total triacylglycerol (P = 0.0361), and higher plasma glucose (P = 0.033). Plasma HDL-cholesterol and insulin concentrations and activities of cholesterol ester transfer protein and phospholipid transfer protein did not differ significantly between the diets. CONCLUSIONS: Compared with fat high in oleic acid, MCT fat unfavorably affected lipid profiles in healthy young men by increasing plasma LDL cholesterol and triacylglycerol. No changes in the activities of phospholipid transfer protein and cholesterol ester transfer protein were evident.     

Plasma lipid and lipoprotein concentrations of men consuming a low-fat, high-fiber diet.

This study assessed the influence of a low-fat, high-fiber diet on blood lipid concentrations of 42 men with desirable or moderately elevated cholesterol concentrations. A low-fat diet (19% fat, 4% saturated fatty acids, 4.6 g fiber/MJ) was compared with a high-fat diet (41% fat, 15% saturated fatty acids, 2.0 g fiber/MJ) and with subjects' self-selected diets. Substituting the low-fat for the high-fat diet decreased total, low-density-lipoprotein, and high-density-lipoprotein cholesterol by 17-20%. Lipid changes between 6 and 10 wk were minor. A reduction in plasma cholesterol of greater than 0.52 mmol/L was achieved with the low-fat diet in 59% of men changing from their self-selected diets and in 79% changing from the high-fat diet. Percent reduction was independent of subjects' cholesterol classification. Results indicate that significant reductions in plasma cholesterol can be achieved by the majority of men committing to a low-fat, high-fiber diet.     

Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men

A randomised crossover study of eight overweight or obese men (aged 24-49 years, BMI 25.5-31.3 kg/m(2)), who followed two diets for 4 weeks each, was performed to determine whether substitution of saturated fat with monounsaturated fat affects body weight and composition. Subjects were provided with all food and beverages as modules (selected ad libitum) of constant macronutrient composition, but differing energy content. The % total energy from saturated fat, monounsaturated fat and polyunsaturated fat was 24, 13 and 3 % respectively on the saturated fatty acid (SFA)-rich diet and 11, 22 and 7 % respectively on the monounsaturated fatty acid (MUFA)-rich diet. MUFA accounted for about 80 % of the unsaturated fats consumed on both diets. Body composition, blood pressure, energy expenditure (resting and postprandial metabolic rates, substrate oxidation rate, physical activity), serum lipids, the fatty acid profile of serum cholesteryl esters and plasma glucose and insulin concentrations were measured before and after each diet period. Significant (P< or =0.05) differences in total cholesterol and the fatty acid composition of serum cholesteryl esters provided evidence of dietary adherence. The men had a lower weight (-2.1 (SE 0.4) kg, P=0.0015) and fat mass (-2.6 (SE 0.6) kg, P=0.0034) at the end of the MUFA-rich diet as compared with values at the end of the SFA-rich diet. No significant differences were detected in energy or fat intake, energy expenditure, substrate oxidation rates or self-reported physical activity. Substituting dietary saturated with unsaturated fat, predominantly MUFA, can induce a small but significant loss of body weight and fat mass without a significant change in total energy or fat intake.     

Digestibility of cocoa butter and corn oil and their influence on fatty acid distribution in rats

The comparative bioavailability of cocoa butter (a predominantly saturated fat) and corn oil (a predominantly unsaturated fat) was determined in male Sprague-Dawley rats by analysis of total fecal lipids following ad libitum feeding of purified diets containing 5, 10 and 20% cocoa butter or corn oil for 2 wk. Fecal lipid elimination was significantly increased (P less than 0.05) in each cocoa butter group when compared with the corresponding corn oil group, resulting in lower digestibility coefficients for cocoa butter (59-72%) than for corn oil (93-97%). Body weight gain and food intake data were similar among all treatment groups. Fecal fatty acid profiles in rats fed corn oil diets consisted primarily of 27-34% palmitic acid (16:0), 22-32% stearic acid (18:0) and 25-37% oleic acid (18:1). Palmitic, oleic and linoleic acids were also the primary fatty acids stored in epididymal fat tissue from corn oil-fed rats. In contrast, fecal fatty acids in animals fed cocoa butter diets consisted of 31-37% palmitic acid and 58-64% stearic acid; oleic acid was the major fatty acid stored in epididymal fat tissue. These results indicate that the decreased digestibility of cocoa butter is largely a result of its fatty acid composition. This reduced bioavailability of cocoa butter may be at least partially responsible for its previously described neutral effect on serum cholesterol.     

Controlled evaluation of fat intake in the Mediterranean diet: comparative activities of olive oil and corn oil on plasma lipids and platelets in high-risk patients

Activities of low-fat diets with olive oil or corn oil on lipids and platelets were studied in 23 middle-aged patients with high atherosclerosis risk for 8 wk. The olive oil diet had a polyunsaturated-saturated ratio of 0.33 vs 1.28 for the corn oil diet. Plasma total cholesterol was reduced with corn oil, but high-density lipoprotein cholesterol levels were lower with corn oil and unchanged or raised by olive. Plasma apolipoprotein B levels were equally reduced by both diets; apolipoprotein AI and the apo AI:B ratio rose only with olive oil. Plasma-glucose levels were lowered significantly with olive oil. Changes in platelet function were characterized by a reduced sensitivity to arachidonic acid (particularly with corn oil) and to collagen (particularly with olive). An olive oil diet with a moderate fat intake (about 30% of total calories) leads to favorable plasma lipoprotein and platelet changes.     

Serum lipid response to the graduated enrichment of a Step I diet with almonds: a randomized feeding trial

BACKGROUND: Frequent consumption of nuts may lower the risk of cardiovascular disease by favorably altering serum lipid and lipoprotein concentrations. OBJECTIVE: We compared the effects of 2 amounts of almond intake with those of a National Cholesterol Education Program Step I diet on serum lipids, lipoproteins, apolipoproteins, and glucose in healthy and mildly hypercholesterolemic adults. DESIGN: In a randomized crossover design, 25 healthy subjects (14 men, 11 women) with a mean (+/- SD) age of 41 +/- 13 y were fed 3 isoenergetic diets for 4 wk each after being fed a 2-wk run-in diet (containing 34% of energy from fat). The experimental diets included a Step I diet, a low-almond diet, and a high-almond diet, in which almonds contributed 0%, 10%, and 20% of total energy, respectively. RESULTS: Inverse relations were observed between the percentage of energy in the diet from almonds and the subject's total cholesterol (P value for trend < 0.001), LDL-cholesterol (P < 0.001), and apolipoprotein B (P < 0.001) concentrations and the ratios of LDL to HDL cholesterol (P < 0.001) and of apolipoprotein B to apolipoprotein A (P < 0.001). Compared with the Step I diet, the high-almond diet reduced total cholesterol (0.24 mmol/L or 4.4%; P = 0.001), LDL cholesterol (0.26 mmol/L or 7.0%; P < 0.001), and apolipoprotein B (6.6 mg/dL or 6.6%; P < 0.001); increased HDL cholesterol (0.02 mmol/L or 1.7%; P = 0.08); and decreased the ratio of LDL to HDL cholesterol (8.8%; P < 0.001). CONCLUSIONS: Isoenergetic incorporation of approximately 68 g of almonds (20% of energy) into an 8368-kJ (2000-kcal) Step I diet markedly improved the serum lipid profile of healthy and mildly hypercholesterolemic adults. Total and LDL-cholesterol concentrations declined with progressively higher intakes of almonds, which suggests a dose-response relation.     

Balance of unsaturated fatty acids is important to a cholesterol-lowering diet: comparison of mid-oleic sunflower oil and olive oil on cardiovascular disease risk factors

OBJECTIVE: To evaluate the effects of a trans fat-free monounsaturated fatty acid-rich vegetable oil (NuSun sunflower oil, National Sunflower Association, Bismark, ND) that is a good source of polyunsaturated fatty acids (PUFA) and low in saturated fatty acids on lipid and lipoprotein levels and oxidative stress. DESIGN: A double-blinded, randomized, three period crossover, controlled feeding study. SUBJECTS/SETTING: Thirty-one men (n=12) and women (n=19) with moderate hypercholesterolemia who were 25 to 64 years of age. INTERVENTION: Experimental diets provided 30% fat (olive oil or NuSun sunflower oil contributed one half of the total fat), 8.3% vs 7.9% saturated fatty acid, 17.2% vs 14.2% monounsaturated fatty acid, and 4.3% vs. 7.7% PUFA (olive oil and NuSun sunflower oil, respectively), and 294 mg cholesterol. The control diet was an average American diet (34% fat, 11.2% saturated fatty acid, 14.9% monounsaturated fatty acid, 7.8% PUFA). Subjects consumed each diet for 4 weeks with a 2-week compliance break before crossing over to another diet. MAIN OUTCOME MEASURES: Lipid and lipoprotein levels were measured, and measures of oxidative stress, including lag time, rate of oxidation, total dienes, and lipid hydroperoxides, were assessed. STATISTICAL ANALYSIS: The mixed model procedure was used to test for main effects of diet, feeding period, and order of diets. Tukey-Kramer adjusted P values were used to determine diet effects. RESULTS: The NuSun sunflower oil diet decreased both total and low-density lipoprotein cholesterol levels compared with the average American diet and the olive oil diet. There was no effect of the olive oil diet compared with the average American diet. Total cholesterol decreased 4.7% and low-density lipoprotein cholesterol decreased 5.8% on the NuSun sunflower oil diet vs the average American diet. There was no effect of the experimental diets on triglyceride levels, rate of oxidation, total dienes, lipid hydroperoxides, or alpha-tocopherol. Lag time was the longest following the olive oil diet and shortest following the NuSun sunflower oil diet. CONCLUSIONS: The higher PUFA content appeared to account for the greater total and low-density lipoprotein cholesterol lowering and reduction in lag time of the NuSun sunflower oil diet. However, the fact that there were no differences in the resulting oxidation products suggests there were no adverse effects on low-density lipoprotein oxidation. Since PUFAs are important for cholesterol lowering, foods that replace saturated fatty acids should include a balance of unsaturated fatty acids.     

Walnuts lower serum cholesterol in Japanese men and women

Recent studies have shown that incorporating moderate quantities of walnuts into the recommended cholesterol-lowering diet in the U.S. decreased serum concentrations of total cholesterol in normal American men. To explore whether walnut consumption would also prove effective as part of the Japanese diet, we studied the effects of walnut consumption on serum lipids and blood pressure in Japanese subjects. We randomly assigned 20 men and 20 women to two mixed natural diets, each to be consumed for 4 wk in a crossover design. Both diets conformed to the average Japanese diet (reference diet) and contained identical foods and macronutrients, except that 12.5% of the energy of the walnut diet was derived from walnuts (43-57 g/d) (offset by lesser amounts of fatty foods, meat and visible fat). Total cholesterol concentration was 0.16 mmol/L lower for men (P = 0.05) and 0.21 mmol/L lower for women (P<0.01) when they consumed the walnut diet than when they consumed the reference diet. The LDL cholesterol concentrations were 0.18 mmol/L lower for men (P = 0.13) and 0.22 mmol/L lower for women (P<0.01) when they consumed the walnut diet. The ratio of LDL cholesterol to HDL cholesterol and the apolipoprotein B concentration were also lowered by the walnut diet (P<0.05). Blood pressures did not differ between the walnut and reference diet periods. Incorporating moderate quantities of walnuts into the average Japanese diet while maintaining the intake of total dietary fat and energy decreases serum total cholesterol concentrations and favorably modifies the lipoprotein profile in Japanese, particularly in women.     

Influence of type and amount of dietary lipid on plasma lipid concentrations in endurance athletes

Changes in plasma total cholesterol, triglyceride, and lipoprotein concentrations were assessed in three male endurance cyclists who consumed isoenergetic diets for 28-day periods in which carbohydrate, polyunsaturated fat, or saturated fat contributed about 50% of the daily energy intake. Dietary cholesterol was similar among the diets. Maximal aerobic capacity was maintained at 62 ml O2/(kg X min). Body weights were held within 3% of admission levels. The polyunsaturated fat diet significantly (p less than 0.05) reduced mean fasting plasma total cholesterol in comparison to the saturated fat and carbohydrate diets (160 versus 254 and 243 mg/dl, respectively). Similarly, the polyunsaturated fat diet depressed (p less than 0.05) mean plasma triglycerides relative to the saturated fat and carbohydrate diets (37 versus 62 and 79 mg/dl, respectively). No significant dietary effects were seen on high-density lipoprotein cholesterol. The observed changes in plasma total cholesterol were not significantly different than the values predicted by the Keys' equation, delta CHL = 1.35(2 delta S-delta P) + 1.5 delta Z. We conclude that under controlled conditions in which physical activity is constant l) dietary lipid differences influence fasting serum lipid and lipoprotein concentrations among men with high energy expenditures, and 2) the Keys' equation gives useful predictions of changes in plasma total cholesterol among vigorous men consuming different types and amounts of dietary lipid.     

Insulin-like growth factor I and low-density-lipoprotein cholesterol in women during high- and low-fat feeding.

In vitro studies suggest that insulin-like growth factor I (IGF-I) may modulate hepatic production and peripheral utilization of lipoproteins. We measured blood concentrations of IGF-I; total, high-density-lipoprotein, and low-density-lipoprotein (LDL) cholesterol; and apolipoproteins in 18 women with above average cholesterol after high- and low-fat diet periods. Total cholesterol fell 6% (P less than 0.02) during the low-fat diet because of reduced concentrations of LDL cholesterol (P less than 0.01). Serum concentrations of IGF-I were inversely correlated with total and LDL cholesterol and apolipoprotein B during both high-fat (r = -0.676, P less than 0.005; r = -0.745, P less than 0.001; and r = -0.504, P less than 0.04, respectively) and low-fat (r = -0.656, P less than 0.005; r = -0.757, P less than 0.001; and r = -0.695, P less than 0.001, respectively) diets. IGF-I increased with reduced fat intake in obese subjects only. Thus, IGF-I may contribute to the regulation of LDL cholesterol in mildly hypercholesterolemic women but may not mediate the beneficial response to reduced fat intake.     

Comparison between physiological effects of konjac-glucomannan and propionate in baboons fed "Western" diets

Dietary fiber and resistant starch are fermented by colonic bacteria to short-chain fatty acids (SCFA) such as acetic, butyric and propionic acid, which the colon absorbs. It has been suggested that the beneficial metabolic effects of dietary fiber may be mediated through propionate. We therefore compared the effects of a soluble dietary fiber concentrate, konjac-glucomannan (K-GM), and of propionate on plasma fibrinogen, serum and liver lipid, glucose tolerance, insulin response and liver glycogen in baboons. Twelve male baboons were fed a "Western" diet with or without K-GM (5%) or sodium propionate (2%) supplements for periods of 9 wk in a crossover, randomized order, with stabilization periods in between. Measurements were taken at baseline and after 4 and 9 wk of each study period. After 9 wk, total serum cholesterol levels were significantly higher than pretest values when baboons consumed the unsupplemented Western diet (25%, p less than 0.05) or the propionate diet (17%, p less than 0.05). Konjac-glucomannan prevented this increase. The high density lipoprotein cholesterol concentration increased with all experimental diets (p less than 0.05). The percentage of total cholesterol as high density lipoprotein cholesterol, was significantly higher with K-GM supplementation than with the other diets. Konjac-glucomannan supplementation also resulted in lower than baseline values for triglycerides (p less than 0.01) and circulating free fatty acids (p less than 0.05) after 9 wk. Only the propionate diet raised serum triglycerides significantly (by 6%) above baseline. Liver cholesterol concentration was 31-34% lower, and the area under the glucose tolerance curve was smaller with K-GM and propionate diets (p less than 0.05) than with the unsupplemented diet.(ABSTRACT TRUNCATED AT 250 WORDS)