Moderate intakes of intact soy protein rich in isoflavones compared with ethanol-extracted soy protein increase HDL but do not influence transforming growth factor beta(1) concentrations and hemostatic risk factors for coronary heart disease in healthy subjects.

BACKGROUND

Soybeans contain estrogenic isoflavones that may influence plasma concentrations of transforming growth factor beta(1) (TGF-beta(1)) and plasma lipid and hemostatic risk factors for coronary heart disease.

OBJECTIVE

We compared the effects of moderate intakes of soy protein containing intact phytoestrogens (high-isoflavone diet) and soy protein from which most of the phytoestrogens had been extracted (low-isoflavone diet) on active TGF-beta(1) concentrations and plasma lipid and hemostatic risk factors for coronary heart disease.

DESIGN

A randomized crossover trial was conducted in 22 young, healthy, normolipidemic subjects (5 men and 17 women) who consumed diets providing 56 or 2 mg isoflavones/d for 17 d each with a 25-d washout period between treatments. Fasting blood samples were obtained on days 13 and 14 of each treatment to measure plasma isoflavone, lipid, fibrinogen, and active TGF-beta(1) concentrations and factor VII coagulant and plasminogen activator inhibitor type 1 activities.

RESULTS

Plasma isoflavone concentrations were 100-999 times greater after the high-isoflavone diet than after the low-isoflavone diet (P < 0.05). Plasma HDL-cholesterol and apolipoprotein A-I concentrations were 4% (95% CI: 1%, 8%) and 6% (95% CI: 3%, 10%) higher, respectively, after the high-isoflavone diet than after the low-isoflavone diet (P < 0.01 for both).

CONCLUSION

Compared with soy protein from which most of the phytoestrogens have been extracted, soy protein with intact phytoestrogens increases HDL-cholesterol and apolipoprotein A-I concentrations but does not influence LDL-cholesterol, TGF-beta(1), or fibrinogen concentrations; factor VII coagulant activity; or plasminogen activator inhibitor type 1 activity in normolipidemic, healthy subjects.