Hypocholesterolemic Effect of Soymilk Supplementation with Usual Diet in Premenopausal Normolipidemic Japanese Women

doi:10.1006/pmed.2000.0714

Preventive Medicine

Volume 31, Issue 4, October 2000, Pages 308-314

https://doi.org/10.1006/pmed.2000.0714 Get rights and content

Abstract

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.

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Soybean products have been popular in the Asian countries for its high protein content (Takatsuka et al., 2000).
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and S.F.), 29 studies remained of which 11 were excluded due to different reasons. Finally, 18 studies (Azadbakht & Nurbakhsh, 2011; Beavers et al., 2009; Eslami et al., 2019; SH Faghih et al., 2011; S Faghih, Hedayati, Abadi, & Kimiagar, 2009; Gardner, Messina, Kiazand, Morris, & Franke, 2007; Keshavarz, Nourieh, Attar, & Azadbakht, 2012; Lukaszuk, Luebbers, & Gordon, 2007; Maleki et al., 2019; Miraghajani et al., 2012; Miraghajani et al., 2013; Mitchell & Collins, 1999; Mohammad‐Shahi, Mowla, Haidari, Zarei, & Choghakhori, 2016; Nourieh et al., 2012; Önning, Åkesson, Öste, & Lundquist, 1998; Onuegbu, Olisekodiaka, Onibon, Adesiyan, & Igbeneghu, 2011; Rivas, Garay, Escanero, Cia Jr, et al., 2002; Takatsuka et al., 2000) with 19 treatment arms were eligible for inclusion in the present meta-analysis. Five studies provided data for FBG (Gardner et al., 2007; Keshavarz et al., 2012; Maleki et al., 2019; Miraghajani et al., 2013; Önning et al., 1998), four articles for insulin (29,30,32, 35), seven trials for body weight (Azadbakht & Nurbakhsh, 2011; Eslami et al., 2019; SH Faghih et al., 2011; Keshavarz et al., 2012; Lukaszuk et al., 2007; Miraghajani et al., 2013; Mohammad‐Shahi et al., 2016), six studies for BMI (Azadbakht & Nurbakhsh, 2011; Eslami et al., 2019; S Faghih et al., 2009; Keshavarz et al., 2012; Lukaszuk et al., 2007; Mohammad‐Shahi et al., 2016), five trials for WC (Azadbakht & Nurbakhsh, 2011; Eslami et al., 2019; S Faghih et al., 2009; Keshavarz et al., 2012; Lukaszuk et al., 2007), five articles for blood pressure (Azadbakht & Nurbakhsh, 2011; Keshavarz et al., 2012; Maleki et al., 2019; Miraghajani et al., 2013; Rivas, Garay, Escanero, Cia Jr, et al., 2002), four studies for CRP (Eslami et al., 2019; Miraghajani et al., 2012; Mohammad‐Shahi et al., 2016; Nourieh et al., 2012) and IL-6 (Beavers et al., 2009; Miraghajani et al., 2012; Mohammad‐Shahi et al., 2016; Nourieh et al., 2012), and three trials for TNF-α (Beavers et al., 2009; Miraghajani et al., 2012; Mohammad‐Shahi et al., 2016) and fibrinogen (Keshavarz et al., 2012; Maleki et al., 2019; Miraghajani et al., 2012).
Soy milk contains some beneficial components such as isoflavones which can exert favorable effects on the cardiovascular health. The current study aimed to comprehensively evaluate the potential effects of soy milk consumption on cardiometabolic risk factors in adults.
Relevant articles published up to June 2020 were systematically retrieved from SCOPUS, PubMed/MEDLINE, EMBASE, and Web of Science databases. In our study, we included all the randomized controlled trials (RCTs) investigating the impact of soy milk consumption on various cardiometabolic risk factors in adults (age ≥ 18 years). A meta-analysis of the eligible studies was performed using the random-effects model.
The quantitative meta-analysis of 18 eligible RCTs (665 participants, age range 18–65 years) demonstrated that the consumption of soy milk significantly reduced systolic (P < 0.001) and diastolic (P = 0.002) blood pressure, total (P = 0.001) and low-density lipoprotein (P = 0.041) cholesterol, waist circumference (P = 0.005), C-reactive protein (P < 0.001), and tumor necrosis factor-alpha (P = 0.016). Significant between-study heterogeneity was found for the pooled effect sizes of blood pressure and low-density lipoprotein cholesterol. In addition, the subgroup analyses indicated that the decrease in systolic blood pressure (SBP) was more pronounced when soy milk was consumed for ≤ 4 weeks. However, there were no significant differences between soy milk and control groups for the other factors, namely body weight, body mass index (BMI), high-density lipoprotein cholesterol, triglycerides, fasting blood glucose (FBG), and fasting insulin, interleukin-6, and fibrinogen.
The current systematic review and meta-analysis revealed that incorporating soy milk into the diet might favorably affect several cardiometabolic risk factors in both healthy and unhealthy individuals.
A meta-analysis of 46 studies identified by the FDA demonstrates that soy protein decreases circulating LDL and total cholesterol concentrations in adults
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Certain plant foods (nuts and soy protein) and food components (viscous fibers and plant sterols) have been permitted by the FDA to carry a heart health claim based on their cholesterol-lowering ability. The FDA is currently considering revoking the heart health claim for soy protein due to a perceived lack of consistent LDL cholesterol reduction in randomized controlled trials.
We performed a meta-analysis of the 46 controlled trials on which the FDA will base its decision to revoke the heart health claim for soy protein.
We included the 46 trials on adult men and women, with baseline circulating LDL cholesterol concentrations ranging from 110 to 201 mg/dL, as identified by the FDA, that studied the effects of soy protein on LDL cholesterol and total cholesterol (TC) compared with non-soy protein. Two independent reviewers extracted relevant data. Data were pooled by the generic inverse variance method with a random effects model and expressed as mean differences with 95% CI. Heterogeneity was assessed and quantified.
Of the 46 trials identified by the FDA, 43 provided data for meta-analyses. Of these, 41 provided data for LDL cholesterol, and all 43 provided data for TC. Soy protein at a median dose of 25 g/d during a median follow-up of 6 wk decreased LDL cholesterol by 4.76 mg/dL (95% CI: −6.71, −2.80 mg/dL, P < 0.0001; I² = 55%, P < 0.0001) and decreased TC by 6.41 mg/dL (95% CI: −9.30, −3.52 mg/dL, P < 0.0001; I² = 74%, P < 0.0001) compared with non-soy protein controls. There was no dose–response effect or evidence of publication bias for either outcome. Inspection of the individual trial estimates indicated most trials (∼75%) showed a reduction in LDL cholesterol (range: −0.77 to −58.60 mg/dL), although only a minority of these were individually statistically significant.
Soy protein significantly reduced LDL cholesterol by approximately 3–4% in adults. Our data support the advice given to the general public internationally to increase plant protein intake. This trial was registered at clinicaltrials.gov as NCT03468127.
Soy milk: A functional beverage with hypocholesterolemic effects? A systematic review of randomized controlled trials
2019, Complementary Therapies in Medicine
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Of the eight studies, 3 22,23,27 did not show any significant improvement in serum lipids following soy milk consumption. While 5 trials 19–21,28,29 reported significant changes in serum levels of TG, TC, LDL-C, and/or HDL-C. Bricarello et al. 19 reported that in comparison to the dairy milk, intake of 1-liter soy milk per day for 6 weeks resulted to a significant increase in serum HDL-C and conversely, a significant decrease in LDL-C in patients with primary hypercholesterolemia. Although, such a favorable effect was not found for serum TC and TG.
Current guidelines have highlighted the role of diet in conjunction with drug therapy in the management of dyslipidemia. Over the last two decades, the effect of soy milk, a derivative of soybean, on blood lipids has been the focus of nutritional researches. The present study aimed to provide a comprehensive review of clinical trials investigating the effect of soy milk on blood lipids.
An electronic database searching including PubMed, EMBASE, Scopus, and CENTRAL was performed to extract all the records that were published up to May 2018 using MeSH terms and relevant keywords. Randomized clinical trials that had evaluated the effect of soy milk consumption on serum lipids including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) were eligible for inclusion to this systematic review.
Eight eligible trials comprising a total of 263 subjects were included in this review. Three studies reported no significant improvement in any of the serum lipid parameters following soy milk consumption. A significant decrease in serum TG, TC, and LDL-C was reported by 1, 1 and 3 trials. Also, 1 trial found that soy milk consumption was accompanied by a significant increase in HDL-C.
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However, the review has not separated the effect of isolated soy protein from soy protein contained in soya food/soy products, and the placebo groups also included non-protein controls. In contrast to our null findings, three clinical trials, with duration ranging from 40 days to 6 months, using soy products containing low dosage of soy protein (8–17 g) (soymilk [8], soy-rich diet [6] or soy protein added with β-sitosterol [7]), reported beneficial effects of soy on lipids, suggesting that the hypocholesterolaemic effect of soy might be due to the synergistic effects of various soy ingredients (unsaturated fatty acid, soy fibre, saponins, sterol, or phytic acid, etc.) other than soy protein alone. Soybean processing can alter the content of many naturally occurring components [25].
Observational studies note that regular dietary soy protein intake (6–11 g day⁻¹) has a significant association with lower blood lipids; however, these observations have not been confirmed by clinical trials. This study aimed to ascertain the effects of moderate intake of soy protein (15 g) with isoflavones or isoflavones alone on serum lipid profiles, inflammatory markers (C-reactive protein and uric acid) and composite cardiovascular risk in Chinese postmenopausal, prediabetic women.
A double-blind randomised, placebo-controlled trial was conducted among 180 postmenopausal Chinese women with prediabetes or early untreated diabetes, aged 46–70 years and, on average, 6.0 years since menopause. Participants were randomly assigned to one of the three arms to receive 15-g soy protein and 100-mg isoflavone (Soy group), or 15-g milk protein and 100 mg isoflavone (Iso group) or 15-g milk protein (placebo group) on a daily basis for 6 months. The results showed that no significant difference was observed in serum high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), total cholesterol (TC), triaclyglycerol (TG), high sensitive C-reactive protein and a composite 10-year cardiovascular risk between the three groups at both 3 and 6 months. Serum uric acid marginally increased by 1.22% in the Soy group and decreased by 4.28% and 4.82% in the Iso and placebo groups at 3 months (P = 0.087), but no difference was observed at 6 months (P = 0.264).
Soy protein with isoflavones or isoflavones alone at the provided dosage showed no significantly beneficial effects on measured cardiovascular risk factors in postmenopausal Chinese women with early hyperglycaemia.

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^☆: Supported by a grant from the Ministry of Health and Welfare, Japan.

²: To whom reprint requests should be addressed. Fax: +81-58-265-9020. E-mail: [email protected].

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Regular ArticleHypocholesterolemic Effect of Soymilk Supplementation with Usual Diet in Premenopausal Normolipidemic Japanese Women☆

Abstract

Lancet

Am J Clin Nutr

Lancet

Am J Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

Am J Clin Nutr

J Lipid Res

Nutr Rep Int

Atherosclerosis

Am J Clin Nutr

J Nutr

J Nutr

J Nutr

Food Chem Toxicol

J Am Diet Assoc

Am J Clin Nutr

Lancet

Am J Clin Nutr

Am J Clin Nutr

Regular Article
Hypocholesterolemic Effect of Soymilk Supplementation with Usual Diet in Premenopausal Normolipidemic Japanese Women☆