Soy isoflavones improve plasma lipids in normocholesterolemic, premenopausal women

Abstract

Background: Soy consumption is known to reduce plasma total cholesterol and LDL cholesterol in hypercholesterolemic subjects, but the responsible soy components and the effects in normocholesterolemic subjects remain unclear. Objective: The effects of soy isoflavone consumption on plasma total cholesterol, HDL-cholesterol, LDL-cholesterol, triacylglycerol, apolipoprotein A-I, apolipoprotein B, and lipoprotein(a) concentrations and on LDL peak particle diameter were examined in normocholesterolemic, premenopausal women. Design: Thirteen healthy, normocholesterolemic, free-living, premenopausal female volunteers took part in this randomized, crossover-controlled trial. Each subject acted as her own control. Three soy isoflavone intakes (control: 10.0 ± 1.1; low: 64.7 ± 9.4; and high: 128.7 ± 15.7 mg/d), provided as soy protein isolate, were consumed for 3 menstrual cycles each. Total cholesterol, HDL cholesterol, LDL cholesterol, and triacylglycerol were measured over the menstrual cycle. Apolipoprotein A-I, apolipoprotein B, lipoprotein(a), and LDL peak particle diameter were evaluated in the midluteal phase. Results: Total cholesterol, HDL-cholesterol, and LDL-cholesterol concentrations changed significantly across menstrual cycle phases (P < 0.005). During specific phases of the cycle, the high-isoflavone diet lowered LDL cholesterol by 7.6-10.0% (P < 0.05), the ratio of total cholesterol to HDL cholesterol by 10.2% (P < 0.005), and the ratio of LDL to HDL cholesterol by 13.8% (P < 0.002). Conclusions: Isoflavones significantly improved the lipid profile across the menstrual cycle in normocholesterolemic, premenopausal women. Although of small magnitude, these effects could contribute to a lower risk of developing coronary heart disease in healthy people who consume soy over many years.

Probiotic capsules do not lower plasma lipids in young women and men

“…Although the clinical characteristics of subjects in the present study may have contributed to the lack of change observed in plasma lipids, other dietary substances (such as soy protein) have been shown to improve plasma lipids in young normocholesterolemic subjects (Wong et al, 1998;Merz-Demlow et al, 2000;McVeigh et al, 2006). In addition, prospective studies have reported a relationship between lipid concentrations within the normal range and future CHD (Klag et al, 1993;Strandberg et al, 2004), and current public health recommendations suggest lower goals for optimal plasma lipid concentrations (Expert Panel, 2001;Grundy et al, 2004).…”

Effect of soy and milk protein supplementation on serum lipid levels: a randomized controlled trial

“…Isoflavones are structurally similar to estradiol and have a high binding affinity for the primary estrogen receptors in the vascular wall, estrogen receptor-a and -b (Kuiper et al, 1998;Hodges et al, 2000;Aavik et al, 2001). Several clinical trials have indicated that isoflavones in soy protein may have an important role in lowering serum lipids (Baum et al, 1998;Crouse et al, 1999;Merz-Demlow et al, 2000;Gardner et al, 2001;Clerici et al, 2007). In addition, epidemiologic studies have documented that the Asian populations who consume soy foods as a dietary staple have a lower incidence of CVD than those who consume a typical Western diet (Beaglehole, 1990;Zhang et al, 2003;Sacks et al, 2006).…”

Comparison of a dietary portfolio diet of cholesterol-lowering foods and a statin on LDL particle size phenotype in hypercholesterolaemic participants

“…Two studies conducted in normocholesterolaemic and mildly hypercholesterolaemic women consuming their habitual diets reported that supplementation with isolated soya protein powder (low or high in isoflavones) had no impact on LDL-PPD 24,25 . We have shown in a more recent controlled study that consumption of soya protein produced an important redistribution of LDL from small to larger particles and a significant reduction in the proportion of LDL with a diameter ,25·5 nm (LDL % ,25·5 nm ) 22 .…”