Beneficial role of dietary phytoestrogens in obesity and diabetes

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 approximately 3%. 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.

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Soy Protein, Isoflavones, and Cardiovascular Health An American Heart Association Science Advisory for Professionals From the Nutrition Committee

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

To review international nutrition recommendations with a special emphasis on carbohydrate and fiber, analyze clinical trial information, and provide an evidence-based recommendation for medical nutrition therapy for individuals with diabetes. Relevant articles were identified by a thorough review of the literature and the data tabulated. Fixed-effects meta-analyses techniques were used to obtain mean estimates of changes in outcome measures in response to diet interventions. Most international organizations recommend that diabetic individuals achieve and maintain a desirable body weight with a body mass index of /=55%; protein, 12-16%; fat, <30%; and monounsaturated fat, 12-15%. The diet should provide 25-50 g/day of dietary fiber (15-25 g/1000 kcal). Glycemic index information should be incorporated into exchanges and teaching material.

Carbohydrate and fiber recommendations for individuals with diabetes: a quantitative assessment and meta-analysis of the evidence.

OBJECTIVE —Phytoestrogen consumption has been shown to reduce risk factors for cardiovascular disease. Type 2 diabetes confers an adverse cardiovascular risk profile particularly in women after menopause. The aim of this study was to determine whether a dietary supplement with soy protein and isoflavones affected insulin resistance, glycemic control, and cardiovascular risk markers in postmenopausal women with type 2 diabetes. RESEARCH DESIGN AND METHODS —A total of 32 postmenopausal women with diet-controlled type 2 diabetes completed a randomized, double blind, cross-over trial of dietary supplementation with phytoestrogens (soy protein 30 g/day, isoflavones 132 mg/day) versus placebo (cellulose 30 g/day) for 12 weeks, separated by a 2-week washout period. RESULTS —Compliance with the dietary supplementation was >90% for both treatment phases. When compared with the mean percentage change from baseline seen after 12 weeks of placebo, phytoestrogen supplementation demonstrated significantly lower mean values for fasting insulin (mean ± SD 8.09 ± 21.9%, P = 0.006), insulin resistance (6.47 ± 27.7%, P = 0.003), HbA 1c (0.64 ± 3.19%, P = 0.048), total cholesterol (4.07 ± 8.13%, P = 0.004), LDL cholesterol (7.09 ± 12.7%, P = 0.001), cholesterol/HDL cholesterol ratio (3.89 ± 11.7%, P = 0.015), and free thyroxine (2.50 ± 8.47%, P = 0.004). No significant change occurred in HDL cholesterol, triglycerides, weight, blood pressure, creatinine, dehydroepiandrosterone sulfate, androstenedione, and the hypothalamic-pituitary-ovarian axis hormones. CONCLUSIONS —These results show that dietary supplementation with soy phytoestrogens favorably alters insulin resistance, glycemic control, and serum lipoproteins in postmenopausal women with type 2 diabetes, thereby improving their cardiovascular risk profile.

https://care.diabetesjournals.org/content/diacare/25/10/1709.full.pdf

Beneficial effects of soy phytoestrogen intake in postmenopausal women with type 2 diabetes.

OBJECTIVE — Consumption of soy protein has recently been shown to improve the blood lipid levels in nondiabetic subjects. The purpose of this study was to evaluate if a dietary supplement of soy protein, isoflavones, and cotyledon fiber (Abalon) affects cardiovascular risk markers, blood glucose, and insulin levels in type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS — Twenty type 2 diabetic subjects participated in a crossover trial. They were randomized to double-blind supplementation for 6 weeks with Abalon (soy protein [50 g/day] with high levels of isoflavones [minimum 165 mg/day] and cotyledon fiber [20 g/day]) or placebo (casein [50 g/day] and cellulose [20 g/day]), separated by a 3-week wash-out period.

RESULTS — The results are expressed as means ± SD. The percentage mean treatment difference between Abalon and placebo demonstrated significantly lower mean values after Abalon for LDL cholesterol (10 ± 15%, P < 0.05), LDL/HDL ratio (12 ± 18%, P < 0.05), apolipoprotein (apo) B100 (30 ± 38%, P < 0.01), triglycerides (22 ± 10%, P < 0.05), and homocysteine (14 ± 21%, P < 0.01), whereas the total cholesterol value tended to be less significant but still lower (8 ± 15%, P < 0.08). No change occurred in HDL cholesterol, apo B100/apo A1 ratio, plasminogen activator inhibitor 1, factor VIIc, von Willebrand factor, fibrinogen, lipoprotein(a), glucose, HbAlc, or 24-h blood pressure.

CONCLUSIONS — These results indicate beneficial effects of dietary supplementation with Abalon on cardiovascular risk markers in type 2 diabetic subjects. This improvement is seen even in individuals with near-normal lipid values.

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Beneficial Effects of a Soy-Based Dietary Supplement on Lipid Levels and Cardiovascular Risk Markers in Type 2 Diabetic Subjects

Objectives: Soy protein intake has favorable effects on body weight and fat distribution in experimental animals but these effects have not been demonstrated in humans. To compare effects of soy- vs. milk-based meal replacements (MR) we assessed weight loss and serum lipoproteins changes for obese subjects who consumed low-energy diets (LED) including either milk-based or soy-based MR.Methods: Overweight or obese women and men (body mass indices 27–40 kg/m2) were randomly assigned to LED providing 1200 kcal/day, with consumption of five soy-based or two milk-based liquid MR for a 12-week weight loss trial. Serum lipoprotein measurements were obtained at baseline, 6 and 12 weeks.Results: For soy and milk MR groups, subject numbers were, respectively, 51 and 39 randomized and 30 and 22 completers. MR use averaged: soy, 3.7/day; and milk, 1.9/day. Weight losses for completers at 12 weeks were: soy MR, 9.0% of initial body weight (95% confidence intervals, 7.3–10.6%); and milk MR, 7.9% (5.8–8.8%) with no sign...

Weight loss and lipid changes with low-energy diets: comparator study of milk-based versus soy-based liquid meal replacement interventions.

Obesity is increasing in epidemic proportions globally while current therapies continue to be suboptimal. In this investigation, weight loss in obese individuals after 24 weeks with different nutrition interventions was compared. The impact of intervention intensity was assessed. Inclusion criteria were established and a comprehensive literature review was performed. These nutrition interventions were identified and analyzable: meal replacements (MRs); energy-restricted (>1500 kcal/d) diets (ERDs); low-energy (800–1500 kcal/d) diets (LEDs); soy very low energy (<800 kcal/d) diets (VLEDs) referred to as SOYs; and VLEDs. Intensity was assessed using the following parameters: physician visits, clinic visits, and hours of class over 24 weeks; an intensity score represents an adjusted sum of the values. Weight losses at 24 weeks as percentage of baseline weights (95% confidence intervals) were as follows: MRs, 9.1% (5.7–12.5); ERDs, 8.5% (4.9–12.1); LEDs, 11.4% (8.9–13.1); SOYs, 16.5% (13.9–19.1); and VLEDs, 21.3% (20.1–22.5). Weight loss with SOYs was significantly greater than with MRs and ERDs; weight loss with VLEDs was significantly greater than with any other diet. Energy intake was the most significant (P<.0001) regression variable related to weight loss; however, the intensity of intervention (P=.0003) was significantly stronger than initial body weight or duration of treatment. Medically supervised VLEDs are the most effective intervention for facilitating substantial weight loss over 24 weeks. SOY may promote more rapid weight loss over the first 8 weeks than other interventions. MRs appear to be equally effective with ERDs and LEDs with lower levels of intervention intensity.

Structured weight-loss programs: Meta-analysis of weight loss at 24 weeks and assessment of effects of intervention intensity

Abnormal lipid levels contribute significantly to the risk of coronary heart disease, a major cardiovascular disease and a serious health problem. Various dietary and pharmacologic treatments have been devised to reduce elevated blood cholesterol levels. Soy protein, soluble fiber, and plant sterol/ester-containing margarines are promising new food-component candidates that may help to realize this goal. Of particular interest in this context is the LDL:HDL ratio, a strong predictor of cardiac events. This report is a review of more than 50 recent trials to determine how such dietary components and garlic affect the LDL:HDL ratio and other lipid parameters. Consumption of new soy products containing high, fixed levels of isoflavones, cotyledon soy fiber, and soy phospholipids (Abacor® and Abalon®) significantly reduced the LDL:HDL ratio by up to 27%. Soluble dietary fibers such as psyllium and beta glucan from oat bran had a variable effect on LDL-cholesterol levels in the studies analyzed. Plant sterol esters, when consumed in margarines, lowered the LDL:HDL ratio by up to 22%. On average, Abacor and Abalon reduced the LDL:HDL ratio by 20%, LDL cholesterol by 15%, total cholesterol by 10%, and triglycerides by 6%, and increased HDL cholesterol by 5%. The new soy-based supplements may therefore play a valuable role in reducing cardiovascular risk.

Effects of soy and other natural products on LDL:HDL ratio and other lipid parameters: a literature review.

Soy protein
is effective in lowering plasma
cholesterol, LDL cholesterol and
triglyceride concentrations. It has
not been conclusively answered,
whether and to what extent other
soy constituents may also contribute
to this effect. To
investigate the change in blood
lipid levels after application of two
soy-based supplements containing
soy protein either without
(SuproSoy®) or with (Abacor®) soy
fiber and phospholipids in a randomized
placebo-controlled triplearmed
study. 121 hypercholesterolemic
adults (66 females,
55 males) were recruited and randomly
assigned to one of three
treatments. Over 8 weeks they received
daily either 25 g soy protein
(as a component of the supplements
Abacor® or SuproSoy®) or
25 g milk protein (as a component
of placebo). Serum lipids were
measured at baseline and after 4, 6
and 8 weeks. After 8 weeks
of supplementation total cholesterol
levels were reduced by
8.0 ± 9.6% (Abacor®) and
3.4 ± 8.3% (SuproSoy®); LDL cholesterol
levels by 9.7 ± 11.7% (Abacor®) and 5.4 ± 11.6%
(SuproSoy®); and Apolipoprotein B
levels by 6.9 ± 14.6% (Abacor®)
and 4.0 ± 12.4 % (SuproSoy®).
Serum levels of HDL cholesterol
and triglycerides remained unchanged. A preparation
combining isolated soy protein
with soy fibers and phospholipids
showed twice the lipid-lowering effect
of a preparation containing
isolated soy protein alone. Therefore,
such soy-based supplements
can be useful in reducing the cardiovascular
risk.

A double-blind placebo-controlled clinical trial compares the cholesterol-lowering effects of two different soy protein preparations in hypercholesterolemic subjects.

Lars H. Hoie

Papers

Beneficial Effects of a Soy-Based Dietary Supplement on Lipid Levels and Cardiovascular Risk Markers in Type 2 Diabetic Subjects

Weight loss and lipid changes with low-energy diets: comparator study of milk-based versus soy-based liquid meal replacement interventions.

Structured weight-loss programs: Meta-analysis of weight loss at 24 weeks and assessment of effects of intervention intensity

Effects of soy and other natural products on LDL:HDL ratio and other lipid parameters: a literature review.

A double-blind placebo-controlled clinical trial compares the cholesterol-lowering effects of two different soy protein preparations in hypercholesterolemic subjects.