Role of Isoflavones in the Hypocholesterolemic Effect of Soy (original) (raw)
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The Journal of nutrition, 2004
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 concentrati...
Critical Reviews in Food Science and Nutrition, 2019
Background: Many randomized controlled trials (RCTs) have assessed the effects of soy products on serum lipids. However, the responsible soy components and the magnitude of effects in healthy or hypercholesterolemic postmenopausal women are unclear. This review assessed the quality of these RCTs and estimated the effects of isolated soy protein, isolated soy isoflavones and soy protein containing isoflavones on total cholesterol (TC), LDL-C, HDL-C, triglycerides (TG), Apolipoprotein (Apo) A-1 and Apo B among postmenopausal women. Design: Forty-six eligible randomized controlled trials published up to 20 May 2019 were identified from the PubMed, Web of Science and Scopus databases. Weighted mean effect sizes were calculated for net changes in serum lipid concentrations by using random-effect models. Specific subgroup analyses were performed to identify the effect of covariates on serum lipid changes. Results: Soy consumption was associated with significant decrease in TG (mean differences (MD): À5.04 mg/dl; 95% CI: À9.95, À0.13; P ¼ 0.044), TC (MD: À3.02 mg/dl; 95% CI: À5.56, À0.47; P ¼ 0.02), LDL-C (MD: À3.27 mg/dl; 95% CI: À6.01, À0.53; P ¼ 0.019) and HDL-C (MD: À2.28 mg/dl; 95% CI: À4.27, À0.29; P ¼ 0.025). The reduction in LDL-C, TG and HDL were larger in subjects consuming isolated soy protein than isolated soy isoflavones. There was a significant decrease in serum TG and HDL levels with dosages of >25 grams per day soy protein rather than lower dosages of soy protein. The reductions in Apo A-1 were significantly larger in hypercholesterolemic subjects than in healthy subjects. Conclusions: Isolated soy protein significantly reduced serum TG, TC, LDL-C, HDL-C and Apo-B levels in postmenopausal women. Isolated soy isoflavones had a significant lowering effect on serum TC and Apo B levels. Soy protein containing isoflavones significantly reduced TG, TC, LDL-C and Apo B levels. Therefore, hyperlipidemia risk reduction with soy products is not uniform and strongly depends on the protein and isoflavone content of soy products, duration and dosage of consumption.
Effect of Soy Isoflavones on the Serum Lipid Profile and Vascular Function
Soybeans are unique among the legumes because they are a concentrated source of isoflavones. A number of components of soy have been studied to investigate their potential effect on CVD. Soy proteins have been shoen to lower LDL-Cholesterol and to have neutral or slightly positive effect on HDL-Chloesterol. However, to what extend actually is the role of the isoflavone in this action remained contradictive. This review describes the characteristics and the nature of the soy isoflavones as well as covering the results from several studies to determine the effect of soy isoflavones on the serum lipid and vascular functions.
The American journal of clinical nutrition, 2002
Many of the benefits of soy have been attributed to soy isoflavones. The objective was to determine the effects of high- and low-isoflavone soy-protein foods on both lipid and nonlipid risk factors for coronary artery disease (CAD). Forty-one hyperlipidemic men and postmenopausal women participated in a study with three 1-mo diets: a low-fat dairy food control diet and high- (50 g soy protein and 73 mg isoflavones daily) and low- (52 g soy protein and 10 mg isoflavones daily) isoflavone soyfood diets. All 3 diets were very low in saturated fat (< 5% of energy) and cholesterol (< 50 mg/d). Fasting blood samples were drawn and blood pressure was measured at the start and end of each diet. No significant differences were seen between the high- and low-isoflavone soy diets. Compared with the control diet, however, both soy diets resulted in significantly lower total cholesterol, estimated CAD risk, and ratios of total to HDL cholesterol, LDL to HDL cholesterol, and apolipoprotein ...
Nutrition and Cancer, 2005
Consumption of soy protein has been associated with altered risk of developing endocrine-regulated cancers. This study was designed to assess the independent effect of soy relative to animal protein and soy-derived isoflavones on circulating estrogen and androgen concentrations in postmenopausal women and older men. Forty-two subjects (> 50 yr) with low-density lipoprotein cholesterol levels of ≥3.36 mmol/l were fed each of 4 diets in randomized order for 6 wk/phase. All food and drink were provided. Diets contained 25 g soy or common sources of animal protein/4.2 MJ containing trace or 50 mg isoflavones/4.2 MJ. At the end of each diet phase, concentrations of estrone sulfate, estrone, estradiol, testosterone, androstendione, dihydrotestosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate were measured. In postmenopausal women, concentrations of estrone were higher and its precursor, dehydroepiandrosterone, lower after consuming the soy compared with animal protein diets (P = 0.0396 and 0.0374, respectively). There was no significant effect of isoflavones on any of the hormones measured. In older men, dehydroepiandrosterone sulfate concentrations were lower after consuming the isoflavone (P = 0.0106) and higher after soy, compared with the animal protein diets (P = 0.0118). These data suggest that relatively large amounts of soy protein or soy-derived isoflavones had modest and limited sex-specific effects on circulating hormone levels.
The Journal of Nutrition, 2004
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 Ͼ 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 Ͻ 0.01). Soy protein also decreased the cholesterol levels in LDL Ͻ 25.5 nm by 12.3% (P Ͻ 0.001) and increased cholesterol levels in LDL Ͼ 26.0 nm by 14.3% (P Ͻ 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.
Effects of soy protein containing isoflavones on women's lipid profile: a meta-analysis
Revista de Nutrição, 2011
This study evaluated the effects of soy protein containing isoflavones on the lipid profile of women. A meta-analysis including 13 eligible randomized controlled trials was carried out. The literature was systematically searched for randomized controlled trials on the effects of soy protein containing isoflavones on the serum lipids of adult women. The main searched databases were PubMed, Cochrane Library, MedLine, Lilacs and Web of Science. Randomized controlled trials were included if they met the following criteria: published from 1966 to 2005, the study population consisted of women only, had either a crossover or a parallel design and the amounts of soy protein and isoflavones consumed were provided. Weighted mean effect sizes were calculated for net changes in serum lipid concentrations using fixed-effects and random-effects models. Prespecified subgroup analyses were performed to explore the influence of covariates on net lipid change. Soy protein with isoflavones was associa...
Arteriosclerosis, Thrombosis, and Vascular Biology, 2006
Soy protein and isoflavones (phytoestrogens) have gained considerable attention for their potential role in improving risk factors for cardiovascular disease. This scientific advisory assesses the more recent work published on soy protein and its component isoflavones. In the majority of 22 randomized trials, isolated soy protein with isoflavones, as compared with milk or other proteins, decreased LDL cholesterol concentrations; the average effect was Ϸ3%. This reduction is very small relative to the large amount of soy protein tested in these studies, averaging 50 g, about half the usual total daily protein intake. No significant effects on HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure were evident. Among 19 studies of soy isoflavones, the average effect on LDL cholesterol and other lipid risk factors was nil. Soy protein and isoflavones have not been shown to lessen vasomotor symptoms of menopause, and results are mixed with regard to soy's ability to slow postmenopausal bone loss. The efficacy and safety of soy isoflavones for preventing or treating cancer of the breast, endometrium, and prostate are not established; evidence from clinical trials is meager and cautionary with regard to a possible adverse effect. For this reason, use of isoflavone supplements in food or pills is not recommended. Thus, earlier research indicating that soy protein has clinically important favorable effects as compared with other proteins has not been confirmed. In contrast, many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat.