Effects of a new low dose soy protein/β-sitosterol association on plasma lipid levels and oxidation

Summary. Background: High doses of soy protein are able to decrease plasma cholesterolemia significantly, but they unbalance daily protein intake and strongly modify nutritional habits in patients. Aim of the study: To evaluate the antihypercholesterolemic efficacy of a low dose soy protein product with added -sitosterol (rapport = 4:1) in 36 moderately hypercholesterolemic subjects. Methods: The study was divided into 3 separate periods of 40 days each: a stabilization diet period, followed by a treatment period during which all subjects took 10 g of the test product once daily and, finally, a wash out period. The following parameters were monitored: weight, dietary habits, plasma lipid levels, glycemia, uric acid, fibrinogenemia and antibodies against oxidized LDL (ox-LDL Ab). Results: From the end of the stabilization diet period to the end of the supplementation with the soy protein product with added -sitosterol we observed a 19.64 ± 20.32 mg/dL, 8.47 ± 54.61 mg/dL, 1.69 ± 10.92 mg/dL, and 7.06 ± 16.66 mg/dL mean ± SD decrease respectively in LDL-C (p < 0.001), TG (p = 0.358), VLDLs (p = 0.358) and apoB (p = 0.016) levels, associated with a 1.31 ± 8.08 mg/dL and 1.03 ± 19.09 mg/dL mean increase respectively in HDLC (p = 0.251) and apoAI (p = 0.749) plasma concentrations. The dietary supplementation did not influence Lp(a) (p = 0.984) and ox-LDL Ab (p = 0.953) plasma levels. A statistically significant correlation was observed for LDL-C plasma levels, between the end of the stabilization diet period and the end of the period of supplementation with soy proteins with added -sitosterols (p < 0.001). Conclusion: Although further long-term clinical studies are necessary before claims can be made regarding the therapeutic effects of the tested formulation, the preliminary findings regarding its efficacy and safety as an antihypercholesterolemic agent are encouraging.     

Long-term blood cholesterol-lowering effects of a dietary fiber supplement.

BACKGROUND: The study evaluated the blood cholesterol-lowering effects of a dietary supplement of water-soluble fibers (guar gum, pectin) and mostly non-water-soluble fibers (soy fiber, pea fiber, corn bran) in subjects with mild to moderate hypercholesterolemia (LDL cholesterol, 3.37-4.92 mmol/L). METHODS: After stabilization for 9 weeks on a National Cholesterol Education Program Step 1 Diet, subjects were randomly assigned to receive 20 g/d of the fiber supplement (n = 87) or matching placebo (n = 82) for 15 weeks and then receive the fiber supplement for 36 weeks. The efficacy analyses included the 125 subjects (58 fiber; 67 placebo) who were treatment and diet compliant. One hundred two (52 fiber; 50 placebo) completed the 15-week comparative phase. Of these subjects 85 (45 fiber; 40 placebo) elected to continue in the 36-week noncomparative extension phase. RESULTS: The mean decreases during the 15-week period for LDL cholesterol (LDL-C), total cholesterol (TC), and LDL-C/HDL-C ratio were greater (P < 0.001) in the fiber group. The mean changes from pre-treatment values in LDL-C, TC, and LDL-C/HDL-C ratio for subjects in the fiber group were -0.51 mmol/L (-12.1%), -0.53 mmol/L (-8.5%), and -0.30 (-9.4%), respectively. The corresponding changes in the placebo group were -0.05 mmol/L (-1.3%), -0.05 mmol/L (-0.8%), and 0.05 (1.5%), respectively. The fiber supplement had no significant effects (P > 0.05) on HDL cholesterol (HDL-C), triglyceride, iron, ferritin, or vitamin A or E levels. Similar effects were seen over the subsequent 36-week noncomparative part of the study. CONCLUSIONS: The fiber supplement provided significant and sustained reductions in LDL-C without reducing HDL-C or increasing triglycerides over the 51-week treatment period.     

Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms

The apparently smaller LDL cholesterol (LDL-C)-lowering effect of soy in recent studies has prompted the U.S. FDA to reexamine the heart health claim previously allowed for soy products. We therefore attempted to estimate the intrinsic and extrinsic (displacement) potential of soy in reducing LDL-C to determine whether the heart health claim for soy continues to be justified. The intrinsic effect of soy was derived from a meta-analysis using soy studies (20-133 g/d soy protein) included in the recent AHA Soy Advisory. The extrinsic effect of soy in displacing foods higher in saturated fat and cholesterol was estimated using predictive equations for LDL-C and NHANES III population survey data with the substitution of 13-58 g/d soy protein for animal protein foods. The meta-analysis of the AHA Soy Advisory data gave a mean LDL-C reduction of 0.17 mmol/L (n = 22; P < 0.0001) or 4.3% for soy, which was confirmed in 11 studies reporting balanced macronutrient profiles. The estimated displacement value of soy (13-58 g/d) using NHANES III population survey data was a 3.6-6.0% reduction in LDL-C due to displacement of saturated fats and cholesterol from animal foods. The LDL-C reduction attributable to the combined intrinsic and extrinsic effects of soy protein foods ranged from 7.9 to 10.3%. Thus, soy remains one of a few food components that reduces serum cholesterol (>4%) when added to the diet.     

Effects of soy as tofu vs meat on lipoprotein concentrations

OBJECTIVES: To investigate the effect of replacing lean meat with a soy product, tofu, on serum lipoprotein concentrations. STUDY AND DESIGN: Randomized cross-over dietary intervention study. SUBJECTS: Forty-two free-living healthy males aged 35-62 y completed the dietary intervention. Three additional subjects were non-compliant and excluded prior to analysis. INTERVENTIONS: A diet containing lean meat (150 g/d) was compared with one with 290 g/d tofu in an isocaloric and isoprotein substitution. Both diet periods were 1 month, and fat intake was carefully controlled. RESULTS: Seven-day diet records showed the two diets were similar in energy, macronutrients and fibre. Total cholesterol (mean difference 0.23 mmol/l, 95% CI 0.02, 0.43; P=0.03) and triglycerides (mean difference 0.15 mmol/l, 95% CI 0.02, 0.31; P=0.017) were significantly lower on the tofu diet than the lean meat diet. However, HDL-C was also significantly lower on the tofu diet (mean difference 0.08 mmol/l, 95% CI 0.02, 0.14; P=0.01) although the LDL-C:HDL-C ratio was similar. CONCLUSION: The effect on HDL-C and the small LDL-C reduction differ from some other studies, where fat was often less controlled, and the comparison was of soy as textured protein or soymilk against casein. This suggests a differential effect of the various proteins compared to the soy may influence the findings. In practice, the replacement of meat with tofu would usually be associated with a decrease in saturated fat and an increase in polyunsaturated fat and this should enhance any small benefits due to the soy protein. SPONSOR: Deakin University with some contribution from a Commonwealth Department of Veterans Affairs research grant. European Journal of Clinical Nutrition (2000) 54, 14-19     

Probiotic consumption does not enhance the cholesterol-lowering effect of soy in postmenopausal women

Numerous studies report that soy lowers cholesterol. Probiotic bacteria were also reported to lower total cholesterol (TC) and LDL cholesterol (LDL-C). We hypothesized that by altering intestinal microflora, probiotic consumption may also change phytoestrogen metabolism and enhance the effects of soy. To evaluate the independent and interactive effects of probiotic bacteria and soy on plasma TC, LDL-C, HDL cholesterol (HDL-C), and triglycerides (TG), 37 women with a baseline TC of 5.24 mmol/L were given the following 4 treatments for 6 wk each in a randomized crossover design: soy protein isolate (26 +/- 5 g soy protein containing 44 +/- 8 mg isoflavones/d); soy protein isolate + probiotic capsules (10(9) colony-forming units Lactobacillus acidophilus DDS-1 and Bifidobacterium longum); milk protein isolate (26 +/- 5 g milk protein/d); and milk protein isolate + probiotic. Soy consumption decreased plasma TC by 2.2% (P = 0.02) and LDL-C by 3.5% (P = 0.005), increased HDL-C by 4.2% (P = 0.006) and tended to decrease TG (P = 0.07) compared with milk protein intake. When divided according to initial TC concentration, soy effects were observed only in hypercholesterolemic women (TC > 5.17 mmol/L). In this subgroup, soy treatments decreased plasma TC by 3.3% (P = 0.01), LDL-C by 4.5% (P = 0.004), and TG by 10.6% (P = 0.02), and increased HDL-C by 4.2% (P = 0.02). When subjects were divided on the basis of plasma and urine concentrations of the isoflavone metabolite, equol, equol producers and nonproducers did not differ in baseline lipids or in the effects of soy. Probiotics did not lower cholesterol or enhance the effects of soy. These results confirm a beneficial effect of soy on plasma cholesterol in mildly hypercholesterolemic postmenopausal women independent of equol production status, but do not support an independent or additive effect of these particular probiotic bacteria.     

Soy food consumption does not lower LDL cholesterol in either equol or nonequol producers

BACKGROUND: Health claims link soy protein (SP) consumption, through plasma cholesterol reduction, to a decreased risk of heart disease. Soy isoflavones (ISOs), particularly in individuals who produce equol, might also contribute to lipid lowering and thus reduce SP requirements. OBJECTIVE: The objective was to examine the contributions of SP, ISOs, and equol to the hypocholesterolemic effects of soy foods. DESIGN: Nonsoy consumers (33 men, 58 women) with a plasma total cholesterol (TChol) concentration >5.5 mmol/L participated in a double-blind, placebo-controlled, crossover intervention trial. The subjects consumed 3 diets for 6 wk each in random order, which consisted of foods providing a daily dose of 1) 24 g SP and 70-80 mg ISOs (diet S); 2) 12 g SP, 12 g dairy protein (DP), and 70-80 mg ISOs (diet SD); and 3) 24 g DP without ISOs (diet D). Fasting plasma TChol, LDL cholesterol, HDL cholesterol, and triglycerides (TGs) were measured after each diet. RESULTS: TChol was 3% lower with the S diet (-0.17 +/- 0.06 mmol/L; P < 0.05) than with the D diet, and TGs were 4% lower with both the S (-0.14 +/- 0.05 mmol/L; P < 0.05) and SD (-0.12 +/- 0.05 mmol/L; P < 0.05) diets. There were no significant effects on LDL cholesterol, HDL cholesterol, or the TChol:HDL cholesterol ratio. On the basis of urinary ISOs, 30 subjects were equol producers. Lipids were not affected significantly by equol production. CONCLUSIONS: Regular consumption of foods providing 24 g SP/d from ISOs had no significant effect on plasma LDL cholesterol in mildly hypercholesterolemic subjects, regardless of equol-producing status.     

Pantethine, a derivative of vitamin B5 used as a nutritional supplement, favorably alters low-density lipoprotein cholesterol metabolism in low- to moderate-cardiovascular risk North American subjects: a triple-blinded placebo and diet-controlled investigation

Safety and efficacy of a biologically active derivative of vitamin B₅ (pantethine) on total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) metabolism was studied in North American subjects at conventional low to moderate cardiovascular disease (CVD) risk. A total of 120 subjects initiated a therapeutic lifestyle change (TLC) diet 4 weeks before randomization (baseline) and maintained the diet throughout a 16-week study period; at baseline, subjects were randomized in a triple-blinded manner to either pantethine (600 mg/d, baseline to week 8, and 900 mg/d, weeks 9-16) or identically labeled, nonbiologically active placebo (n = 60 per group). We hypothesized that pantethine would lower TC and low-density lipoprotein in low-CVD-risk North American subjects in a similar manner as reported in high-CVD-risk subjects studied mainly in Italy and Japan. While sustaining a TLC diet and in comparison with placebo, pantethine demonstrated significant (P < .005) and sustained reductions (from baseline to week 16) in TC (6 mg/dL, 0.16 mmol/L, 3%), LDL-C (4 mg/dL, 0.10 mmol/L, 4%), and apolipoprotein B (4 mg/dL, 0.04 g/L, 5%). Our data suggest that pantethine supplementation for 16 weeks (600 mg/d for weeks 1-8 then 900 mg/d for weeks 9-16) is safe and significantly lowers TC and LDL-C over and above the effect of TLC diet alone. Although the absolute magnitude of these effects was small in these low- to moderate-risk North Americans (4-6 mg/dL), the results are noteworthy as prior studies have shown that, for each 1 mg/dL (0.026 mmol/L) reduction in LDL-C, there is a concomitant 1% reduction in overall future CVD risk.     

Dietary medium-chain triacylglycerol prevents the postprandial rise of plasma triacylglycerols but induces hypercholesterolemia in primary hypertriglyceridemic subjects

BACKGROUND: Previous studies showed divergent results concerning the influence of medium-chain triacylglycerol (MCT) on lipoprotein metabolism. OBJECTIVE: The objective of this study was to compare the effects of MCT and corn oil on plasma lipids in primary hypertriglyceridemic patients. DESIGN: Ten subjects ate different proportions of corn oil and MCT for 12 wk. The subjects first ate a low-fat diet for 2 wk and during the next 4 wk, corn oil was added as the sole source of fat. Thereafter, for 2-wk periods, the subjects were sequentially fed corn oil and MCT mixed in the following proportions: 3:1, 1:1, and 0:1. Fasting plasma total cholesterol, triacylglycerol, and HDL-cholesterol concentrations were measured at the end of each period. At the end of the 100%-corn oil and of the 100%-MCT periods, subjects were fed a test meal containing the respective oil (40 g fat/m(2) body surface area) and total cholesterol and triacylglycerols were measured at 2-h intervals over 8 h; fasting lipoprotein composition was also measured. RESULTS: Compared with corn oil, MCT was associated with a higher mean (+/-SD) fasting total cholesterol concentration (6.39 +/- 1.14 compared with 5.51 +/- 0.98 mmol/L, respectively; P < 0. 05); non-HDL-cholesterol concentrations were also higher with MCT (5. 36 +/- 1.11 mmol/L) than with corn oil (4.51 +/- 0.92 mmol/L; P < 0. 005). In response to the liquid test meal, plasma total cholesterol did not change with either diet but triacylglycerols increased with the 100%-corn oil diet. CONCLUSIONS: MCT prevents the risk of pancreatitis due to postprandial hypertriglyceridemia but has the inconvenience of raising total cholesterol concentrations in primary hypertriglyceridemic subjects.     

Soy isoflavone intake lowers serum LDL cholesterol: a meta-analysis of 8 randomized controlled trials in humans

Clinical trials have noted hypocholesterolemic effects of soy protein intake, but the components responsible are not known. This meta-analysis of 8 randomized controlled trials was conducted to more precisely evaluate the effects of isoflavones on blood LDL cholesterol concentration independently of soy protein level. PubMed was searched for English-language "randomized controlled trial" articles published from 1966 to 2003 that described the effects of soy protein isolate (SPI) intake with measured isoflavone levels on blood lipids in humans using the search terms "soy protein," "isoflavones," and "cholesterol." From 31 articles identified by the search, 8 articles (with 10 low vs. high isoflavone comparisons) were selected for the meta-analysis. Subjects in each comparison consumed similar dietary fat, cholesterol, and fiber; the reported body weight of subjects did not change significantly during treatment. Serum LDL cholesterol concentration in subjects who consumed SPI (mean 50 g/d) with high isoflavone content (mean intake 96 mg/d) decreased by 0.15 mmol/L (95% CI: 0.08 to 0.23 mmol/L; P < 0.0001) compared with those who consumed the same SPI level with low isoflavone content (mean intake 6 mg/d). Decreases in serum LDL cholesterol concentration in hypercholesterolemic and normocholesterolemic subjects were 0.18 mmol/L (95% CI: 0.01 to 0.35 mmol/L; P = 0.03) and 0.14 mmol/L (95% CI: 0.06, 0.23 mmol/L; P = 0.0008), respectively. With identical soy protein intake, high isoflavone intake led to significantly greater decreases in serum LDL cholesterol than low isoflavone intake, demonstrating that isoflavones have LDL cholesterol-lowering effects independent of soy protein.     

A comparison of the effects of 2 doses of soy protein or casein on serum lipids,serum lipoproteins,and plasma total homocysteine in hypercholesterolemic subjects

BACKGROUND: Studies have shown that soy protein reduces some atherogenic lipid and lipoprotein concentrations, although lipoprotein(a) concentrations may be increased. The dose response of soy protein has not been established; neither has its effect on plasma total homocysteine. OBJECTIVE: Our objective was to evaluate the effect of 2 doses of soy protein on lipid, lipoprotein, and homocysteine concentrations. DESIGN: Four to 24 wk after being instructed to consume a lipid-lowering diet, 130 men and women with LDL-cholesterol concentrations > or = 4 mmol/L were studied during a parallel group trial in which 4 interventions were assigned randomly. Thirty grams isolated soy protein (ISP) and 10 g cotyledon fiber or 50 g ISP and 16.6 g cotyledon fiber or equivalent doses of casein and cellulose were consumed daily as a beverage for 16 wk. RESULTS: When the 2 groups who consumed ISP were compared with the 2 groups who consumed casein, the differences in the net changes from baseline to week 16 in the concentrations of LDL cholesterol and plasma total homocysteine were -0.26 mmol/L (95% CI: -0.43, -0.09 mmol/L; P = 0.01) and -0.8 micromol/L (-1.4, -0.2 micromol/L; P = 0.005), respectively. The effect of the ISP dose was not significant. There were no significant differences between the 2 ISP and the 2 casein groups in changes in lipoprotein(a), HDL-cholesterol, or triacylglycerol concentrations. CONCLUSIONS: Adding 30-50 g soy protein/d to a lipid-lowering diet significantly reduced LDL-cholesterol concentrations without increasing lipoprotein(a) concentrations. Plasma total homocysteine concentrations also decreased, suggesting a novel, possibly antiatherosclerotic effect.     

Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile

BACKGROUND: Convincing evidence shows that soy protein intake has beneficial effects on lipid changes, but it is unclear which components of soy protein are responsible. OBJECTIVE: We conducted a meta-analysis to identify and quantify the effects of soy protein containing isoflavones on the lipid profile. DESIGN: Twenty-three eligible randomized controlled trials published from 1995 to 2002 were identified from the PUBMED database (National Library of Medicine, Bethesda, MD). Weighted mean effect sizes were calculated for net changes in serum lipid concentrations by using fixed-effect or random-effect models. Pre-specified subgroup analyses were performed to explore the influence of covariates on net lipid change. RESULTS: Soy protein with isoflavones intact was associated with significant decreases in serum total cholesterol (by 0.22 mmol/L, or 3.77%), LDL cholesterol (by 0.21 mmol/L, or 5.25%), and triacylglycerols (by 0.10 mmol/L, or 7.27%) and significant increases in serum HDL cholesterol (by 0.04 mmol/L, or 3.03%). The reductions in total and LDL cholesterol were larger in men than in women. Initial total cholesterol concentrations had a powerful effect on changes in total and HDL cholesterol, especially in subjects with hypercholesterolemia. Studies with intakes >80 mg showed better effects on the lipid profile. The strongest lowering effects of soy protein containing isoflavones on total cholesterol, LDL cholesterol, and triacylglycerol occurred within the short initial period of intervention, whereas improvements in HDL cholesterol were only observed in studies of >12 wk duration. Tablets containing extracted soy isoflavones did not have a significant effect on total cholesterol reduction. CONCLUSIONS: Soy protein containing isoflavones significantly reduced serum total cholesterol, LDL cholesterol, and triacylglycerol and significantly increased HDL cholesterol, but the changes were related to the level and duration of intake and the sex and initial serum lipid concentrations of the subjects.     

Soy isoflavones lower serum total and LDL cholesterol in humans: a meta-analysis of 11 randomized controlled trials

BACKGROUND: Clinical trials have reported the cholesterol-lowering effects of soy protein intake, but the components responsible are not known. OBJECTIVE: This meta-analysis was primarily conducted to evaluate the precise effects of soy isoflavones on lipid profiles. The effects of soy protein that contains enriched and depleted isoflavones were also examined. DESIGN: PUBMED was searched for English-language reports of randomized controlled trials published from 1990 to 2006 that described the effects of soy protein intake in humans. Eleven studies were selected for the meta-analysis. RESULTS: Soy isoflavones significantly decreased serum total cholesterol by 0.10 mmol/L (3.9 mg/dL or 1.77%; P = 0.02) and LDL cholesterol by 0.13 mmol/L (5.0 mg/dL or 3.58%; P < 0.0001); no significant changes in HDL cholesterol and triacylglycerol were found. Isoflavone-depleted soy protein significantly decreased LDL cholesterol by 0.10 mmol/L (3.9 mg/dL or 2.77%; P = 0.03). Soy protein that contained enriched isoflavones significantly decreased LDL cholesterol by 0.18 mmol/L (7.0 mg/dL or 4.98%; P < 0.0001) and significantly increased HDL cholesterol by 0.04 mmol/L (1.6 mg/dL or 3.00%; P = 0.05). The reductions in LDL cholesterol were larger in the hypercholesterolemic subcategory than in the normocholesterolemic subcategory, but no significant linear correlations were observed between reductions and the starting values. No significant linear correlations were found between reductions in LDL cholesterol and soy protein ingestion or isoflavone intakes. CONCLUSIONS: Soy isoflavones significantly reduced serum total and LDL cholesterol but did not change HDL cholesterol and triacylglycerol. Soy protein that contained enriched or depleted isoflavones also significantly improved lipid profiles. Reductions in LDL cholesterol were larger in hypercholesterolemic than in normocholesterolemic subjects.     

Lipid response to a low-fat diet with or without soy is modified by C-reactive protein status in moderately hypercholesterolemic adults

Recent evidence suggests that individuals with high concentrations of C-reactive protein (CRP), a marker of inflammation, are less responsive to cholesterol-lowering diets. CRP concentrations are increased by oral estrogen; however, the effect of soy phytoestrogens on inflammation has not been studied comprehensively, especially in women receiving hormone replacement therapy (HRT). This study was conducted to determine whether adding soy to a low-fat, high-fiber diet affects CRP and interleukin (IL)-6, and to examine the association between CRP levels and lipid response in moderately hypercholesterolemic adults (men = 18, postmenopausal women = 14; 6 receiving HRT). After a 3-wk run-in period with consumption of a Step I diet (27% total fat, 7% saturated fat, 275 mg cholesterol), participants were randomly assigned to diets containing 25 g/d soy protein (+ 90 mg/d isoflavones) or 25 g/d milk protein for 6 wk in a crossover design. Lipids and lipoproteins, CRP, and IL-6 were measured at the end of each diet and participants were categorized into high (>3.5 mg/L) or low CRP groups based on a median split. The addition of soy or milk protein to the Step I diet did not affect lipids or inflammatory markers. Regardless of protein source, those with low CRP exhibited significant decreases in LDL cholesterol (-3.5%) and the LDL:HDL cholesterol ratio (-4.8%), whereas those with high CRP had significant increases in LDL cholesterol (+4.8%), the LDL:HDL cholesterol ratio (+5.2%), apolipoprotein B (+3.8%), and lipoprotein(a) (+13.5%) compared with the run-in diet. These results suggest that inflammation may not only attenuate lipid responses, but also aggravate dyslipidemia in hypercholesterolemic subjects consuming a cholesterol-lowering diet.     

Pasta naturally enriched with isoflavone aglycons from soy germ reduces serum lipids and improves markers of cardiovascular risk

Most studies of soy and cholesterol have tested foods made from purified soy proteins containing mainly isoflavone glycosides. Fermented soy foods have mainly isoflavone aglycons and account for a high proportion of the soy protein source in Asia, where there is an inverse relationship between soy intake and serum cholesterol. The aim of this study was to compare a novel soy germ pasta, naturally enriched in isoflavone aglycons as a result of the manufacturing process, with conventional pasta for effects on serum lipids and other cardiovascular risk markers. In this randomized, controlled, parallel study design of 62 adults with hypercholesterolemia who consumed a Step II diet that included one 80-g serving/d of pasta, we measured serum lipids, high sensitivity C-reactive protein (hsCRP), urinary isoprostanes, and brachial artery flow-mediated vasodilatation at baseline and after 4 and 8 wk. The pasta delivered 33 mg of isoflavones and negligible soy protein and led to a serum isoflavone concentration of 222 +/- 21 nmol/L; 69% of subjects were equol producers. Soy germ pasta reduced serum total and LDL cholesterol by 0.47 +/- 0.13 mmol/L (P = 0.001) and 0.36 +/- 0.10 mmol/L (P = 0.002) more than conventional pasta, representing reductions from baseline of 7.3% (P = 0.001) and 8.6% (P = 0.002), respectively. Arterial stiffness (P = 0.003) and hsCRP (P = 0.03) decreased and improvements in all the above risk markers were greatest in equol producers. All measures returned to baseline when patients were switched to conventional pasta. In conclusion, pasta naturally enriched with isoflavone aglycons and lacking soy protein had a significant hypocholesterolemic effect beyond a Step II diet and improved other cardiovascular risk markers.     

Soy protein and casein in cholesterol-enriched diets: effects on plasma lipoproteins in normolipidemic subjects

The effect of dietary plant protein vs animal protein on plasma lipoproteins was investigated in a crossover study. Eleven normal subjects consumed formula diets containing 20% of calories as soy protein or casein, 27% as fat, and 53% as carbohydrate: the average cholesterol intake was 500 mg/d. After an initial decrease in plasma cholesterol and low-density-lipoprotein cholesterol (LDL-C) on both diets, the concentration of LDL-C stabilized during the soy-protein diet at a 16% lower level than on the casein diet (p less than 0.02) whereas the concentration of high-density-lipoprotein cholesterol (HDL-C) was 16% higher (p less than 0.01). In a similar earlier study with a cholesterol intake of less than 100 mg/d, casein and soy protein had indistinguishable effects on lipoprotein levels. Our two studies together suggest that the level of cholesterol intake may determine whether plant and animal dietary proteins have similar or different effects on plasma LDL and HDL concentrations.     

Soy protein favorably affects LDL size independently of isoflavones in hypercholesterolemic men and women

We assessed the independent effect of soy protein relative to animal protein and of isoflavones on various electrophoretic characteristics of LDL particles. LDL particles were characterized by polyacrylamide gradient gel electrophoresis in 36 moderately hypercholesterolemic men and women (LDL cholesterol > 3.36 mmol/L). All subjects consumed in random order each of the four diets (soy protein depleted of isoflavones, soy protein enriched in isoflavones, animal protein with no added isoflavones, and animal protein with added isoflavones) for 6 wk. Consumption of soy protein was associated with a larger LDL peak particle size relative to animal protein (P < 0.01). Soy protein also decreased the cholesterol levels in LDL < 25.5 nm by 12.3% (P < 0.001) and increased cholesterol levels in LDL > 26.0 nm by 14.3% (P < 0.05) relative to animal protein. Isoflavones did not affect these LDL particle characteristics. Soy protein shifted LDL particle distribution to a less atherogenic pattern and this effect is independent of soy's isoflavone component.     

Hypocholesterolemic effect of soymilk supplementation with usual diet in premenopausal normolipidemic Japanese women

BACKGROUND: The hypocholesterolemic effect of soy protein concentrates on normolipidemic subjects still remains unclear. Our objective is to assess the effect of soymilk supplementation, a whole soy product, with usual diet on serum lipids in normolipidemic subjects. METHODS: We conducted a randomized controlled trial on 60 premenopausal normolipidemic Japanese women. After excluding 8 subjects whose initial serum concentration of total cholesterol or triacylglycerol was higher than 220 mg/dL (5.69 mmol/L) or 160 mg/dL (1.81 mmol/L), respectively, we encouraged the subjects in the soymilk-supplemented group (n = 27) to consume 400 mL (408 g) of commercial regular soymilk daily during two menstrual cycles. There were no significant differences in variables, including nutrient intake, between the soymilk-supplemented and control (n = 25) groups before the intervention. RESULTS: After the trial, we observed a significant decrease of 10.9 mg/dL, or 5.3%, in serum concentration of total cholesterol in the soymilk-supplemented group. During the intervention, nutrient intake assessment showed significant increases in nutrient densities of vitamin E, polyunsaturated fatty acids, isoflavones, and P/S ratio and decreases in total energy and nutrient densities of vitamin C and green tea in this group. A statistically significant decrease in serum total cholesterol could still be observed even after excluding the estimated hypocholesterolemic effects of soymilk's polyunsaturated fatty acids. CONCLUSIONS: Our results suggest the hypocholesterolemic effect of soymilk, a traditional whole soy product, in Asian countries in normolipidemic subjects.     

Oats and soy in lipid-lowering diets for women with hypercholesterolemia: is there synergy?

OBJECTIVES: To study possible synergistic effects of oats and soy on reducing total and low-density lipoprotein cholesterol (LDL-C) concentrations in human beings and the efficacy and feasibility of including these adjustments to a National Cholesterol Education Program Step I diet. SUBJECT/SETTING: One hundred twenty-seven postmenopausal women with moderate hypercholesterolemia were recruited from a large Midwestern workforce and senior centers in the surrounding community. Intervention and clinical visits were conducted in these same facilities. DESIGN: After a 3-week lead-in period on the Step I diet, participants were randomly assigned to 1 of 4 dietary treatments for an additional 6 weeks: an oats/milk group, a wheat/soy group, an oats/soy group, and a wheat/milk group. Clinical measurements included blood draws, body weight and height, blood pressure, and medical history data. Three-day food records were collected at baseline and Weeks 3 and 9 of the intervention. Randomization was stratified based on the status of hormone replacement therapy and was blocked with sizes 4 or 8 for group assignment. RESULTS: After 3 weeks on the Step I diet, total cholesterol, LDL-C, and triglyceride levels; total fat and saturated fat intake, dietary cholesterol intake, Keys score, and body mass index were all reduced. Following an additional 6 weeks on the Step I diet plus intervention, total cholesterol and LDL-C were further reduced for both the oats/soy group and oats/milk group. There were no significant further changes in total cholesterol, LDL-C, or high-density lipoprotein cholesterol levels in the wheat/soy and wheat/milk groups. Body mass index remained stable in all groups from Week 3 to Week 9. APPLICATIONS: Nonpharmacologic dietary interventions like the Step I diet are feasible in a community setting and can produce rapid and significant lipid-lowering benefits. Daily consumption of 2 servings of oats can contribute to further lipid alterations in this population although soy intake at this dose may not. Palatability and convenience are important considerations in achieving dietary adherence.     

大豆肽对大鼠离体工作心脏血流动力学的影响

目的:观察大豆肽对正常和经异丙肾上腺素预处理的大鼠离体工作心脏的作用。方法:采用改良的Langendorff心脏灌流装置,通过主动脉压力(AP),心室内压(LVSP),舒末压(LVEDP),左室内压最大上升或下降速率(±dp/dtmax),主动脉流量(AF),冠脉流量(CF),心率(HR)等血流动力学指标的变化来考察大豆肽0.03、0.10和0.30 mmol/L对正常大鼠离体工作心脏和0.1 mmol/L大豆肽对经异丙肾上腺素预处理的大鼠离体工作心脏的影响。结果:大豆肽0.03、0.10和0.30 mmol/L皆能降低正常大鼠AP,LVSP,LVEDP,±dp/dtmax,AF,并且增加CF,而对HR没有明显的影响;大豆肽0.1 mmol/L能降低经异丙肾上腺素处理的大鼠离体工作心脏AP,LVSP,LVEDP,±dp/dtmax和HR。结论:大豆肽具有负性肌力作用,且能拮抗异丙肾上腺素对大鼠离体工作心脏的正性肌力作用。     

Fat-free foods supplemented with soy stanol-lecithin powder reduce cholesterol absorption and LDL cholesterol

OBJECTIVE: The objective of this work was to show that fat-free, lecithin-formulated soy stanols lower cholesterol absorption and serum LDL cholesterol. DESIGN: Reduction in cholesterol absorption was measured in paired single-meal tests with or without formulated soy stanols (acute test), and changes in serum lipids were investigated in a 10-week, randomized, double-blind parallel trial in which formulated stanols or lecithin vehicle were given three times daily for the last 4 weeks (chronic test). SUBJECTS/SETTING: Forty-five normal or mildly hypercholesterolemic subjects were recruited for both studies. The 21 subjects (16 female, 5 male; mean age 32.5 years) in the absorption studies had the following mean lipid values: LDL cholesterol, 2.79 mmol/L and total cholesterol, 4.73 mmol/L. For the lipid reduction, 24 subjects (16 female, 8 male; mean age 50.6 years) were enrolled with mean LDL cholesterol and total cholesterol of 3.72 mmol/L and 5.66 mmol/L, respectively. INTERVENTION: Reduction in cholesterol absorption was measured using a lemonade beverage or egg whites that contained 625 mg stanols. Throughout the chronic study, subjects followed the American Heart Association Step I diet. During the 4-week treatment phase, subjects consumed daily a lemonade-flavored beverage containing either placebo or formulated soy stanols (1.9 g). MAIN OUTCOME MEASURES: Inhibition of cholesterol absorption was determined from the difference in plasma deuterated cholesterol enrichment after a test meal containing stanol-lecithin and one with lecithin vehicle only. In the chronic study, the primary endpoints were changes in LDL and total cholesterol. STATISTICAL ANALYSES PERFORMED: Paired or unpaired t tests were used to determine statistical significance. RESULTS: Stanol-lecithin reduced cholesterol absorption by 32.1% (P=.0045, n=10) and by 38.2% (P=.0022, n=11) when delivered in a lemonade-flavored beverage and in egg whites, respectively. Reduction in cholesterol absorption was strongly related to the initial level of absorbed cholesterol tracer in serum (r(s)=-0.739). Stanol-lecithin given in a beverage reduced total serum cholesterol by 10.1% (P=.0019, n=24) and LDL cholesterol by 14.3% (P=.0016, n=24). APPLICATIONS/CONCLUSIONS: Powdered soy stanol-lecithin lowers cholesterol absorption and LDL cholesterol when consumed in fat-free foods.