High-monounsaturated fatty acid diets lower both plasma cholesterol and triacylglycerol concentrations

BACKGROUND: Low-fat diets increase plasma triacylglycerol and decrease HDL-cholesterol concentrations, thereby potentially adversely affecting cardiovascular disease (CVD) risk. High-monounsaturated fatty acid (MUFA), cholesterol-lowering diets do not raise triacylglycerol or lower HDL cholesterol, but little is known about how peanut products, a rich source of MUFAs, affect CVD risk. OBJECTIVE: The present study compared the CVD risk profile of an Average American diet (AAD) with those of 4 cholesterol-lowering diets: an American Heart Association/National Cholesterol Education Program Step II diet and 3 high-MUFA diets [olive oil (OO), peanut oil (PO), and peanuts and peanut butter (PPB)]. DESIGN: A randomized, double-blind, 5-period crossover study design (n = 22) was used to examine the effects of the diets on serum lipids and lipoproteins: AAD [34% fat; 16% saturated fatty acids (SFAs), 11% MUFAs], Step II (25% fat; 7% SFAs, 12% MUFAs), OO (34% fat; 7% SFAs, 21% MUFAs), PO (34% fat; 7% SFAs, 17% MUFAs), and PPB (36% fat; 8% SFAs, 18% MUFAs). RESULTS: The high-MUFA diets lowered total cholesterol by 10% and LDL cholesterol by 14%. This response was comparable with that observed for the Step II diet. Triacylglycerol concentrations were 13% lower in subjects consuming the high-MUFA diets and were 11% higher with the Step II diet than with the AAD. The high-MUFA diets did not lower HDL cholesterol whereas the Step II diet lowered it by 4% compared with the AAD. The OO, PO, and PPB diets decreased CVD risk by an estimated 25%, 16%, and 21%, respectively, whereas the Step II diet lowered CVD risk by 12%. CONCLUSION: A high-MUFA, cholesterol-lowering diet may be preferable to a low-fat diet because of more favorable effects on the CVD risk profile.     

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.     

Fish consumption shifts lipoprotein subfractions to a less atherogenic pattern in humans

The effect of fish consumption on plasma lipoprotein subfraction concentrations was studied in 22 men and women (age > 40 y). Subjects were provided an average American diet (AAD, 35% of energy as fat, 14% as saturated fat, and 35 mg cholesterol/MJ) for 6 wk before being assigned to a National Cholesterol Education Program (NCEP) Step 2 high-fish diet (n = 11, 26% of energy as fat, 4.5% as saturated fat, and 15 mg cholesterol/MJ) or a NCEP Step 2 low-fish diet (n = 11, 26% of energy as fat, 4.0% as saturated fat, and 11 mg cholesterol/MJ) for 24 wk. All food and drink were provided to study participants. Consumption of the high-fish NCEP Step 2 diet was associated with a significant reduction in medium and small VLDL, compared with the AAD diet, whereas the low-fish diet did not affect VLDL subfractions. Both diets significantly reduced LDL cholesterol concentrations, without modifying LDL subfractions. Both diets also lowered HDL cholesterol concentrations. However, the high-fish diet significantly lowered only the HDL fraction containing both apolipoprotein (apo) AI and AII (LpAI:AII) and did not change HDL subfractions assessed by NMR, whereas the low-fish diet significantly lowered the HDL fraction containing only apo AI (LpAI) and the large NMR HDL fractions, resulting in a significant reduction in HDL particle size. Neither diet affected VLDL and LDL particle size. Our data indicate that within the context of a diet restricted in fat and cholesterol, a higher fish content favorably affects VLDL and HDL subspecies.     

Low-fat and high-monounsaturated fatty acid diets decrease plasma cholesterol ester transfer protein concentrations in young, healthy, normolipemic men

BACKGROUND: Cholesterol ester transfer protein (CETP) mediates the transfer of cholesteryl esters from HDL to apolipoprotein (apo) B-containing lipoproteins. The possible atherogenic role of this protein is controversial. Diet may influence plasma CETP concentrations. OBJECTIVE: The objective was to determine whether the changes in plasma lipids observed after consumption of 2 lipid-lowering diets are associated with changes in plasma CETP concentrations. DESIGN:: We studied 41 healthy, normolipidemic men over 3 consecutive 4-wk dietary periods: a saturated fatty acid-rich diet (SFA diet: 38% fat, 20% saturated fat), a National Cholesterol Education Program Step I diet (NCEP Step I diet: 28% fat, 10% saturated fat), and a monounsaturated fatty acid-rich diet (MUFA diet: 38% fat, 22% monounsaturated fat). Cholesterol content (27.5 mg/MJ) was kept constant during the 3 periods. Plasma concentrations of total, LDL, and HDL cholesterol; triacylglycerol; apo A-I and B; and CETP were measured at the end of each dietary period. RESULTS: Compared with the SFA diet, both lipid-lowering diets significantly decreased plasma total and LDL cholesterol, apo B, and CETP. Only the NCEP Step I diet lowered plasma HDL cholesterol. Positive, significant correlations were found between plasma CETP and total (r = 0.3868, P < 0.0001) and LDL (r = 0.4454, P < 0.0001) cholesterol and also between changes in CETP concentrations and those of total (r = 0.4543, P < 0.0001) and LDL (r = 0.4554, P < 0.0001) cholesterol. CONCLUSIONS: The isoenergetic substitution of a high-saturated fatty acid diet with an NCEP Step I or a high-monounsaturated fatty acid diet decreases plasma CETP concentrations.     

Nutritional intake of women and men on the NCEP Step I and Step II diets.

Restriction of dietary fat and cholesterol are recommended for treating hyperlipidemia, but may alter vitamin or mineral intakes. We evaluated changes in nutrients of individuals taught the National Cholesterol Education Program (NCEP) Step II diet.

Subjects participated in a randomized controlled trial of the cholesterol-lowering effect of the NCEP Step II diet. Eligibility criteria included elevated fasting plasma LDL-cholesterol, no lipid-altering medications, and diet not already fat-modified. Subjects attended eight weekly dietitian-led classes. Four-day food records collected 6 months post-intervention were compared to baseline records.

Of 409 subjects with complete data, 123 met Step I and 166 met Step II diet criteria. Intakes of micronutrients associated with fruits and vegetables (beta-carotene and vitamin A, vitamin C, folic acid, magnesium, and potassium) increased on both diets. Patterns of decreased mean intake and/or fewer subjects consuming 2/3 Recommended Dietary Allowance were seen for calcium, vitamin E, and zinc.

NCEP Step I and II diets generally match or exceed unmodified diet for vitamin and mineral content. Premenopausal women do not appear to be at increased risk of low iron intake. Vitamin E intake decreases, although the significance is unknown in the context of lower fat intake and increased intake of other antioxidants. Diet counseling and materials should encourage sources of calcium for women, and zinc for both women and men.     

A controlled 2-mo dietary fat reduction and soy food supplementation study in postmenopausal women

BACKGROUND: Low intake of dietary fat and high intake of soy foods have been suggested to partly explain the lower breast cancer rates in Asia, perhaps because of lower endogenous estrogens. OBJECTIVE: The objective was to assess the hormonal and nonhormonal effects of diets resembling an Asian diet in terms of total fat and soy food contents. DESIGN: Fifty-seven postmenopausal women participated in a randomized, controlled, dietary intervention study. The subjects consumed a very-low-fat diet (VLFD; 11% of energy as fat), a Step I diet (25% of energy as fat) supplemented with soy food (SFD; 50 mg isoflavones/d), or a control Step I diet (CD; 27% of energy as fat) with no soy food. All diets were prepared at the General Clinical Research Center of the University of Southern California. Serum hormones and other markers were measured at baseline and every 2 wk during the 8 wk of intervention. RESULTS: There were no significant differences in total estradiol and sex hormone binding globulin at the completion of the intervention between women in the SFD and VLFD groups and those in the CD group. Serum insulin decreased significantly in the SFD group, and leptin decreased significantly in the SFD and VLFD groups; however, these changes did not differ significantly from the changes in the CD group. CONCLUSIONS: This study does not provide evidence that ingestion of soy food or a VLFD significantly reduces estrogen concentrations in postmenopausal women. However, short-term changes in diet may have significant and beneficial effects on blood insulin and leptin concentrations.     

What are the long‐term benefits of weight reducing diets in adults? A systematic review of randomized controlled trials

BACKGROUND: Evidence is needed for the best long-term diet for weight loss, and improvement in cardiac risk and disease in obese adults. METHODS: We systematically reviewed randomized controlled trials (RCTs) in any language. We searched 13 databases and handsearched journals. Trials lasted 1 year or more. One investigator extracted the data and a second checked data extraction. Trial quality was assessed. RESULTS: Low fat diets (LFDs) produced significant weight losses up to 36 months (-3.55 kg; 95% CI, -4.54 to -2.55 kg). Blood pressure, lipids and fasting plasma glucose improved with these diets after 12 months. Four studies found that LFDs may prevent type 2 diabetes and reduce antihypertensive medication for up to 3 years. A very low calorie diet (VLCD, < 4.2 MJ day(-1)) was associated with the most weight loss after 12 months (-13.40 kg; 95% CI, -18.43 to -8.37 kg) in one small study with beneficial effects on asthma. There was no evidence that low carbohydrate protein sparing modified fasts (PSMFs) were associated with greater long-term weight loss than low calorie diets (LCDs, 4.2-6.7 MJ day(-1)) or VLCDs. PSMFs were, however, associated with greater lowering of fasting plasma glucose and HbA1c than LCDs. CONCLUSIONS: Little evidence supports the use of diets other than LFDs for weight reduction. With the increasing prevalence of morbid obesity, long-term follow-up in RCTs is needed to evaluate the effect of LCDs, VLCDs and PSMFs more fully.     

A monounsaturated fatty acid-rich pecan-enriched diet favorably alters the serum lipid profile of healthy men and women

Frequent consumption of nuts is associated with decreased risk of cardiovascular disease. We investigated the effect of pecans rich in monounsaturated fat as an alternative to the Step 1 diet in modifying serum lipids and lipoproteins in men and women with normal to moderately high serum cholesterol. In a single-blind, randomized, controlled, crossover feeding study, we assigned 23 subjects (mean age: 38 y; 9 women, 14 men) to follow two diets, each for 4 wk: a Step I diet and a pecan-enriched diet (accomplished by proportionately reducing all food items in a Step I diet by one fifth for a 20% isoenergetic replacement with pecans). The percentage of energy from fat in the two diets was 28.3 and 39.6%, respectively. Both diets improved the lipid profile; however, the pecan-enriched diet decreased both serum total and LDL cholesterol by 0.32 mmol/L (6.7 and 10.4%, respectively) and triglyceride by 0.14 mmol/L (11.1%) beyond the Step I diet, while increasing HDL cholesterol by 0.06 mmol/L (2.5 mg/dL). Serum apolipoprotein B and lipoprotein(a) decreased by 11.6 and 11.1%, respectively, and apolipoprotein A1 increased by 2.2% when subjects consumed the pecan compared with the Step I diet. These differences were all significant (P < 0.05). A 20% isoenergetic replacement of a Step I diet with pecans favorably altered the serum lipid profile beyond the Step I diet, without increasing body weight. Nuts such as pecans that are rich in monounsaturated fat may therefore be recommended as part of prescribed cholesterol-lowering diet of patients or habitual diet of healthy individuals.     

Comparison of monounsaturated fat with carbohydrates as a replacement for saturated fat in subjects with a high metabolic risk profile: studies in the fasting and postprandial states

BACKGROUND: In subjects with a high prevalence of metabolic risk abnormalities, the preferred replacement for saturated fat is unresolved. OBJECTIVE: The objective was to study whether carbohydrate or monounsaturated fat is a preferred replacement for saturated fat. DESIGN: Fifty-two men and 33 women, selected to have any combination of HDL cholesterol < or = 30th percentile, triacylglycerol > or = 70th percentile, or insulin > or = 70th percentile, were enrolled in a 3-period, 7-wk randomized crossover study. The subjects consumed an average American diet (AAD; 36% of energy from fat) and 2 additional diets in which 7% of energy from saturated fat was replaced with either carbohydrate (CHO diet) or monounsaturated fatty acids (MUFA diet). RESULTS: Relative to the AAD, LDL cholesterol was lower with both the CHO (-7.0%) and MUFA (-6.3%) diets, whereas the difference in HDL cholesterol was smaller during the MUFA diet (-4.3%) than during the CHO diet (-7.2%). Plasma triacylglycerols tended to be lower with the MUFA diet, but were significantly higher with the CHO diet. Although dietary lipid responses varied on the basis of baseline lipid profiles, the response to diet did not differ between subjects with or without the metabolic syndrome or with or without insulin resistance. Postprandial triacylglycerol concentrations did not differ significantly between the diets. Lipoprotein(a) concentrations increased with both the CHO (20%) and MUFA (11%) diets relative to the AAD. CONCLUSIONS: In the study population, who were at increased risk of coronary artery disease, MUFA provided a greater reduction in risk as a replacement for saturated fat than did carbohydrate.     

Low fat and high monounsaturated fat diets decrease human low density lipoprotein oxidative susceptibility in vitro

Oxidative modification of low density lipoprotein (LDL) is thought to play an important role in the development of atherosclerosis. Some studies have found that LDL enriched in monounsaturated fatty acids (MUFA) are less susceptible to oxidation than LDL enriched in polyunsaturated fatty acids (PUFA). A high MUFA diet is an alternative to a lower-fat blood cholesterol-lowering diet. Less is known about the effects of high MUFA versus lower-fat blood cholesterol-lowering diets on LDL oxidative susceptibility. The present study was designed to evaluate the effects of men and women consuming diets high in MUFA (peanuts plus peanut butter, peanut oil and olive oil) on LDL oxidative susceptibility, and to compare these effects with those of a Step II blood cholesterol-lowering diet. A randomized, double-blind, five-period crossover design (n = 20) was used to study the effects of the following diets on LDL-oxidation: average American [35% fat, 15% saturated fatty acids (SFA)], Step II (25% fat, 7% SFA), olive oil (35% fat, 7% SFA), peanut oil (35% fat, 7% SFA) and peanuts plus peanut butter (35% fat, 8% SFA). The average American diet resulted in the shortest lag time (57 +/- 6 min) for LDL oxidized ex vivo, whereas the Step II, olive oil and peanuts plus peanut butter diets resulted in a lag time of 66 +/- 6 min (P < or = 0.1). The slower rate of oxidation [nmol dienes/(min x mg LDL protein)] observed when subjects consumed the olive oil diet (24 +/- 2) versus the average American (28 +/- 2), peanut oil (28 +/- 2) and peanuts plus peanut butter diets (29 +/- 2; P < or = 0.05) was associated with a lower LDL PUFA content. The results of this study suggest that lower-fat and higher-fat blood cholesterol-lowering diets high in MUFA have similar effects on LDL oxidative resistance. In addition, our results suggest that different high MUFA sources varying in the ratio of MUFA to PUFA can be incorporated into a high MUFA diet without increasing the susceptibility of LDL to oxidation.     

Lowering dietary saturated fat and total fat reduces the oxidative susceptibility of LDL in healthy men and women

The present study examined the effects of reducing dietary total fat and saturated fat (SFA) on LDL oxidative susceptibility in 27 healthy men and women (age 24-65 y). Each subject consumed each of three diets for 8 wk: an average American diet (AAD, 34% energy from fat, 15% from SFA), a Step-1 diet (29% fat, 9% SFA) and a very low SFA diet (Low-Sat, 25% fat, 6% SFA). In vitro LDL oxidation was assessed by copper-mediated oxidation, as measured by the kinetics of conjugated diene formation and lipid peroxide formation. Compared with the AAD, plasma LDL-cholesterol (LDL-C) and HDL cholesterol levels were 8% lower (P: = 0.16 and P: = 0.11, respectively), in subjects when they consumed the Step-1 diet and 11% (P: < 0.03) and 14% (P: < 0.057) lower, respectively, when they consumed the Low-Sat diet. Conjugated diene production and oxidation rate were 7% (P: < 0. 05) and 9% (P: < 0.05) lower, respectively. The reduction of lipid peroxide formation was 9% (P: < 0.05) in subjects when they consumed the Low-Sat diet vs. the AAD. In addition, lipid peroxide and conjugated diene formation were positively correlated with plasma total and LDL-C and apolipoprotein B (apo B) levels (r = 0.5-0.6, P: < 0.001), suggesting that quantity of LDL is an important determinant of oxidative modification. Furthermore, at the same level of apo B or LDL-C, LDL from subjects when they consumed either Step-1 or Low-Sat diets was less susceptible (P: < 0.05) to oxidation than those when they consumed the AAD, suggesting that qualitative changes also affect LDL oxidative susceptibility. Therefore, the benefits of lowering dietary SFA may extend beyond decreasing LDL-C levels and include favorable qualitative changes in LDL that further decrease risk of coronary heart disease.     

Reducing total dietary fat without reducing saturated fatty acids does not significantly lower total plasma cholesterol concentrations in normal males.

Forty-eight healthy male students ate an average American diet (AAD) with 37% of calories from fat and 16% from saturated fatty acids for 3 wk. During the next 7 wk, one-third of the students continued to eat the AAD, one-third switched to a 30%-fat diet with 9% saturated fatty acids (Step 1 diet), and one-third switched to a 30%-fat diet with 14% saturated fatty acids (Sat diet). The Step 1 group had a significant reduction in plasma total cholesterol (TC) (0.36 +/- 0.37 mmol/L) compared with the AAD group (0.07 +/- 0.39 mmol/L) and the Sat group (0.08 +/- 0.25 mmol/L). The Sat group did not differ from the AAD group. Changes in low-density-lipoprotein (LDL) cholesterol paralleled changes in total cholesterol. High-density-lipoprotein cholesterol fell significantly in the Step 1 group (0.11 +/- 0.08 mmol/L) compared with the AAD group. Plasma triglycerides did not differ between groups at the end of the randomized periods. In summary, reduction of dietary fat intake from 37% to 30% of calories did not lower plasma total and LDL cholesterol concentrations unless the reduction in total fat was achieved by decreasing saturated fatty acids.     

Iron supplementation does not affect the susceptibility of LDL to oxidative modification in women with low iron status

Elevated iron stores may or may not promote atherogenesis by increasing free radical formation and oxidative stress, but controlled diet and supplement trials are lacking. We tested the hypothesis that iron supplementation does not increase the susceptibility of LDL to undergo oxidative modification in women with low iron status. A randomized, double-blind, 2-period crossover study design (n=26) was used to examine the effects of the following diets on measures of LDL oxidation: average American diet (AAD) [36% of energy as fat; 15% saturated fatty acids (SFA)], and a Step 2 diet (26% fat; 7% SFA). In addition, subjects received either a supplement containing 160 mg of ferrous sulfate (50 mg elemental iron) or a placebo twice daily [supplement group received a total of 320 mg ferrous sulfate (100 mg elemental iron) daily]. After supplementation, serum ferritin differed between the supplement and placebo groups (P=0.008). Measures of LDL oxidation were not affected by supplement intake; however, they were affected by diet. Lag time was shorter after the women consumed the AAD diet than after the Step 2 diet (P<0.0001). The diets did not affect the rate of oxidation or total dienes. Although iron status was improved by aggressive iron supplementation, LDL oxidative susceptibility was not affected. As expected, lag time was increased after the women consumed the low fat, low SFA diet. Therefore, the results of this study do not support a relationship between iron status and LDL oxidation.     

Lipids significantly reduced by diets containing barley in moderately hypercholesterolemic men

OBJECTIVE: To determine whether barley, as the soluble fiber source, would beneficially change cardiovascular risk factors. Soluble fiber from oats has been recognized as beneficial in decreasing blood cholesterol levels. Although barley contains high amounts of soluble fiber, it is not consumed as extensively as oats. METHODS: Eighteen moderately hypercholesterolemic men (28-62 y) consumed a controlled equilibration diet (Step 1, 30% fat, 55% carbohydrate, 15% protein, < 300 mg cholesterol) for 2 weeks followed by the diet with about 20% of energy replaced with brown rice/whole wheat, (1/2) barley & (1/2) brown rice/whole wheat or barley (< 0.4 g, 3 g and 6 g added soluble fiber/2800 kcal, respectively) for 5 weeks in a Latin square design. Fasting blood was drawn twice weekly. Total cholesterol, HDL cholesterol, and triacylglycerols were measured enzymatically and lipid fractions were measured by nuclear magnetic resonance spectroscopy. RESULTS: Compared with prestudy concentrations, total cholesterol (14%, 17%, and 20%, respectively) and LDL cholesterol (17%, 17%, and 24%, respectively) were significantly lower (p < 0.0001) after the low, medium, and high-soluble fiber diets. Triacylglycerol was 6%, 10%, and 16% lower (p = 0.09) whereas HDL cholesterol (9%, 7%, and 18%) was higher (p < 0.001) after the experimental diets. Total cholesterol and LDL cholesterol after the high-soluble fiber diet were significantly lower than concentrations after the low- or medium-soluble fiber diets. Mean LDL particle number significantly decreased (p < 0.007) and the large LDL cholesterol fraction showed a trend toward lower concentrations (p = 0.06). CONCLUSION: Increasing soluble fiber through consumption of barley in a healthy diet can reduce cardiovascular risk factors.     

Sterol and nutrient excretion in ileostomists on prudent diets.

Nine ileostomists eating three diets (STAND, RESAT and EXFIB) were investigated in order to quantify the changes in sterol and nutrient excretion when shifting between a standard Western diet and two prudent diets. The RESAT diet had a moderate reduction in fat content to 30 per cent of energy, mainly through a reduction in saturated fat. The EXFIB diet had the same fat modification but in addition the dietary fibre content was raised to 3g/MJ according to current Swedish nutrition recommendations. The RESAT diet resulted in a lowered excretion of fat, but the excretion of nitrogen, energy, cholesterol and bile acids did not change compared with the STAND diet. The EXFIB diet resulted in a higher excretion of fat, nitrogen, energy and cholesterol compared with both the STAND and the RESAT diets (P less than 0.01). Bile acids showed no consistent excretion changes. Thus, a prudent diet, with moderate restricted total and saturated fat content, and a moderate increase in dietary fibre from natural food items, increased the excretion of cholesterol and fat from the small bowel when given to healthy ileostomists. A solely fat-modified prudent diet did not significantly change the pattern of excretion compared with a standard diet.     

Men and women differ in lipoprotein response to dietary saturated fat and cholesterol restriction

A diet restricted in saturated fat and cholesterol is recommended for subjects with elevated LDL cholesterol concentrations before and during drug therapy. Gender differences in lipoprotein subspecies response to such diets have not been studied in detail. We examined the effects of a diet low in total fat, saturated fat and cholesterol (Therapeutic Lifestyle Changes, TLC, diet: 26% of energy as fat, 4% as saturated fat, and 45 mg cholesterol/4.2 MJ), compared with an average American diet (AAD: 35% of energy as fat, 14% as saturated fat, and 147 mg cholesterol/4.2 MJ), on plasma lipoprotein subspecies in men and women. Each diet period lasted 6 wk. Body weight was kept constant during each diet period. Men (n = 19) and postmenopausal women (n = 14) >40 y old with moderate hypercholesterolemia participated in this study. Plasma lipoprotein concentrations were assessed by standardized methodology, and lipoprotein sizes were determined by gradient gel electrophoresis and NMR spectroscopy. The TLC diet resulted in greater reductions in total cholesterol and plasma apolipoprotein B concentrations in men than in women (-19% vs. -12%, P < 0.05, and -18% vs. -9%, P < 0.05, respectively). Postprandial triacylglycerol and LpAI:AII concentrations were reduced in men, but not in women (-15% vs. 8%, P < 0.05, and -9% vs. -2%, respectively, P < 0.05). Similar decreases in LpAI concentrations and LDL and HDL particle size were observed in men and women. These data are consistent with the concept that middle aged/elderly men may have a more favorable lipoprotein response to a low fat, low cholesterol diet than postmenopausal women.     

Effects of pistachios on cardiovascular disease risk factors and potential mechanisms of action: a dose-response study

BACKGROUND: Nut consumption lowers cardiovascular disease (CVD) risk. Studies are lacking about the effects of pistachios, a nutrient-dense nut, on CVD risk factors, dose-response relations, and lipid-lowering mechanisms. OBJECTIVE: We evaluated the effects of 2 doses of pistachios, added to a lower-fat diet, on lipids and lipoproteins, apolipoprotein (apo)-defined lipoprotein subclasses, and plasma fatty acids. To investigate the mechanisms of action, we measured cholesteryl ester transfer protein and indexes of plasma stearoyl-CoA desaturase activity (SCD). DESIGN: In a randomized crossover controlled-feeding study, 28 individuals with LDL cholesterol > or = 2.86 mmol/L consumed 3 isoenergetic diets for 4 wk each. Baseline measures were assessed after 2 wk of a typical Western diet. The experimental diets included a lower-fat control diet with no pistachios [25% total fat; 8% saturated fatty acids (SFAs), 9% monounsaturated fatty acids (MUFAs), and 5% polyunsaturated fatty acids (PUFAs)], 1 serving/d of a pistachio diet (1 PD; 10% of energy from pistachios; 30% total fat; 8% SFAs, 12% MUFAs, and 6% PUFAs), and 2 servings/d of a pistachio diet (2 PD; 20% of energy from pistachios; 34% total fat; 8% SFAs, 15% MUFAs, and 8% PUFAs). RESULTS: The 2 PD decreased (P < 0.05 compared with the control diet) total cholesterol (-8%), LDL cholesterol (-11.6%), non-HDL cholesterol (-11%), apo B (-4%), apo B/apo A-I (-4%), and plasma SCD activity (-1%). The 1 PD and 2 PD, respectively, elicited a dose-dependent lowering (P < 0.05) of total cholesterol/HDL cholesterol (-1% and -8%), LDL cholesterol/HDL cholesterol (-3% and -11%), and non-HDL cholesterol/HDL cholesterol (-2% and -10%). CONCLUSIONS: Inclusion of pistachios in a healthy diet beneficially affects CVD risk factors in a dose-dependent manner, which may reflect effects on SCD.     

Consumption of a high-fat diet containing lard during the growth period in rats predisposes them to favorably respond to the diet in later life

To investigate whether preferential fat intake by adult rats could be linked to fat-feeding of rats during the growth period, this paper describes the next two studies. Three groups of 4-wk-old male rats in study 1 received one of three diets: control diet (CTD), low-fat high-carbohydrate diet (LFD), and high-fat low-carbohydrate diet (HFD). After 6 wk (dietary treatment period), 6 rats in each of the groups were sacrificed and the remaining rats were placed on a self-selection regimen of fat-protein diet (FPD) and carbohydrate-protein diet (CPD) for 3 wk (self-selection period). After the dietary treatment period, liver weight and plasma insulin concentration of the LFD group and perirenal fat tissue weight and plasma triacylglycerol and leptin concentrations of the HFD group were higher than those of the CTD group. Although no significant difference in fat energy ratio (F ratio) of combination diets self-selected by the three groups was observed, the F ratios of the combination diets were higher than that of the CTD. After the self-selection period, liver weight and plasma insulin concentration of the LFD group and plasma triacylglycerol concentrations of the HFD group decreased. These data suggested that the dietary selection pattern of the rats was associated with a reduced basal plasma insulin concentration. Three groups of rats in study 2 were placed on a self-selection regimen of the LFD and the HFD after being fed one of three diets (LFD, CTD and HFD) for 6 wk. Although the F ratio of the combination diet consumed by the CTD and the LFD groups was similar to that of the combination diet consumed by rats in study 1, the F ratio of the combination diet consumed by the HFD group was higher than that of other groups. These findings suggest that consumption of the fatty food during the growth period predisposed them to favorably respond to the diet that had become familiar to them in later life.     

Increased intake of fruit and vegetables and a low-fat diet, with and without low-fat plant sterol-enriched spread consumption: effects on plasma lipoprotein and carotenoid metabolism

BACKGROUND: Regular intake of plant sterol (phytosterol)-enriched foods enhances the cholesterol lowering effect of diets. One side effect associated with plant sterol consumption is a modest reduction in plasma carotenoid concentrations. This study investigated the effect of consuming a low-fat National Cholesterol Education Programme (NCEP) Step 1 diet, including a low-fat plant sterol ester (PSE)-enriched spread on cholesterol metabolism to determine if specific dietary advice to increase daily fruit and vegetable intake could prevent reduced plasma carotenoid concentrations. MATERIALS AND METHODS: In this randomised, crossover double-blind trial, 48 hypercholesterolaemic men received 21 g day(-1) of a low-fat PSE-enriched spread or placebo for 3 weeks, interrupted by 3 weeks washout. Individuals also adhered to a NCEP Step 1 diet and repeated 3-day food diaries monitored adherence. Specific advice was provided to increase dietary fruit and vegetable intakes. Fasting blood samples were collected at pre- and post-intervention for lipoprotein and carotenoid analysis. RESULTS: Plasma total and low-density lipoprotein (LDL) cholesterol concentrations were significantly (P <0.05) reduced, by 4.6 and 7.1%, respectively, after the PSE-enriched low-fat spread. Plasma apo B concentrations were significantly (P <0.0005) lower after the PSE spread. PSE consumption was also associated with significantly (P <0.05) lower total plasma beta-carotene concentrations, but this change was not significant after lipid standardisation. PSE consumption had no effect on retinol, alpha-carotene, gamma-tocopherol, alpha-tocopherol, lutein, zeaxanthin, beta-crypyoxanthin or lycopene concentrations. CONCLUSION: Dietary advice to increase daily fruit and vegetable consumption may be effective in preventing a reduction in plasma carotenoid concentrations previously associated with PSE consumption. Further, PSE incorporated in a low-fat spread and consumed as part of a NCEP Step 1 diet are effective in reducing total and LDL cholesterol.     

Effect of synthetic triglycerides of myristic, palmitic, and stearic acid on serum lipoprotein metabolism.

OBJECTIVES: To determine relative effects of diets high in synthetic sources of myristic (14:0), palmitic (16:0) or stearic (18:0) acid on concentrations and metabolism of serum lipoproteins. DESIGN: Eighteen healthy women participated in a three-way cross-over study for five week periods separated by seven week washout periods, diets were assigned in random order. SUBJECTS: Premenopausal women, not on medication, were from three races (Caucasian, African-American, Asian) and four apolipoprotein E phenotype groups (3/3, 3/2, 4/3, and 4/2). INTERVENTION: During the first week the subjects consumed a baseline diet providing 11 energy (en)% saturated fat, 10en% polyunsaturated fat and 14en% monounsaturated fat. Followed by test diets with 19en% saturated fat (including 14en% test saturated fatty acid), 3en% polyunsaturated fat, and 14en% monounsaturated fat for four weeks. Synthetic fats (trimyristin, tripalmitin, and tristearin) were used in blends with natural fats and oils. RESULTS: Mean concentrations of serum total, esterified and LDL cholesterol were significantly lower after 18:0 than after 16:0 (n = 16-18, P < 0.01 for treatment effect). Myristic acid (14:0) had an intermediate effect. Receptor-mediated degradation of 125I-LDL in mononuclear cells obtained from the subjects was lower after 16:0 than after 14:0 and 18:0 (n = 16-18, P=0.05 for treatment effect). Differences in the digestibilities of the fats were not a major factor in the results. Strong cholesterolemic responses to the 16:0 diet were partly explained by apoE phenotype. CONCLUSIONS: As noted previously, stearic acid was neutral compared to 14:0 and 16:0. In contrast to studies involving natural fats, 14:0, fed as a synthetic triglyceride, was less cholesterolemic than 16:0 in a majority of subjects. ApoE phenotype influenced the cholesterolemic response particularly when diets high in 16:0 were eaten.