Effects of Soy Protein Isoflavones on Lipid Profile and Serum Hormones in Hypercholesterolemic Men

Isoflavones are a group of phytoestrogens found mainly in soy bean and its products.Their actions on various tissues have motivated researchers to assess the possible related mechanisms and functions. The main objective of this study is to determine the metaboliceffects of purified alcohol-extracted soy protein isoflavones (SPI) on serum lipoproteinsand hormones of mild to moderate hypercholesterolemic male subjects. The effects of SPI on this type of patients and on the serum hormone levels have not been evaluated previously. 30 male volunteers were randomly divided into two groups in a doubleblind parallel randomized placebo-controlled trial (n=15). Group 1 received 50mg purified alcohol- extracted soy isoflavones solution and group 2 received placebo in a similarly colored solution for an 8-week period. Both groups were matched for age, duration of illness, medications, and diet. Data on other variables of each subject i.e. body mass index, smoking habits, blood pressure, and past medical history were also collected. LDL-, VLDL-, and HDL-cholesterol, Tg and thyroxine, triiodothyronine, FSH, testosterone and fasting blood sugar levels did not change significantly compared to their baseline levels. Total cholesterol decreased by 10 percent, (p=0.055). TSH levels in SPI group showed a significant rise after intervention (p<0.05), remaining, however,within normal range. These results indicate that alcoholextracted SPI without soy protein does not affect serum lipid profiles and hormones in hypercholesterolemic men. More trials with larger number of subjects conducted over a longer period of study are needed to confirm these findings.