de Santana MB, Mandarino MG, Cardoso JR, et al.. Association between soy and green tea (Camellia sinensis) diminishes hypercholesterolemia and increases total plasma antioxidant potential in dyslipidemic subjects. Nutrition., 2008;24: 562-568.

The food industry has shown an increasing interest in polyphenols (e.g., isoflavones and flavonoid found in tea [Camellia sinensis], wine [Vitis vinifera], and soy [Glycine max] products) because of their strong antioxidant potential, abundance in nature, and probable role in the prevention of several disorders associated with oxidative stress, such as cardiovascular disease, cancer, and neurodegenerative disorders. Polyphenols are "the most promising natural antioxidants" in terms of preventing atherogenic development, and their beneficial effects depend on the amount consumed and on bioavailability. Many studies have determined that the hypocholesterolemic effects of vegetable protein consumption, particularly soy, are attributable to the resultant increase in the fecal excretion of steroids. A high fecal excretion of steroids is thought to potentially increase biliary acid production from cholesterol, which results in a reduction in plasma cholesterol. The objective of this study was to evaluate the hypolipidemic and antioxidant effects of soy and green tea, independently and in combination, in dyslipidemic subjects.

One hundred men (n = 39) and women (n = 61) with a mean age of 52.2 plus/minus 12.2 years were recruited from a cardiology clinic in Londrina, Paraná, Brazil, and randomly assigned to 1 of 4 groups: soy group (n = 25; 50 g/day of kinako spread over 3 meals; 31.2 mg of isoflavones), green tea group (n = 25; 3 g in 500 mL of water/day ingested throughout the day; 145 mg of epigallocatechin-3-gallate), soy/green tea group (n = 25; same as soy and green tea groups), and control group (n = 25; standard hypocholesterolemic diet). The soy product was provided by the Brazilian Farming Research Company (Londrina, Paraná, Brazil), and the green tea was provided by Yamamotoyama (Midori Indústria de Chá Ltda., São Paulo, Brazil). The following variables were measured in all subjects at baseline and after 45 and 90 days of the intervention: body mass index, abdominal circumference, lipid concentrations, total plasma antioxidant capacity (TRAP), and lipid hydroperoxide formation.

TRAP improved significantly (P < 0.05) from baseline in the green tea, soy, and soy/green tea groups after 45 days of the intervention and in the green tea and soy/green tea groups after 90 days of the intervention; TRAP worsened in the control group at both 45 and 90 days. TRAP improved significantly by 17% in the green tea group after 90 days of the intervention. No significant differences in lipid hydroperoxide concentrations, in anthropometric measures, or in triglyceride, high-density-lipoprotein (HDL), and low-density-lipoprotein (LDL) concentrations were observed, except for a significant decrease in total cholesterol from baseline at 45 days (P = 0.002) and 90 days (P = 0.028) in the soy/green tea group.

The consumption of soy and green tea, independently or in combination, improved TRAP in the hypocholesterolemic subjects studied; however, only the combined consumption of these foods decreased total cholesterol concentrations. The lack of significant changes in HDL and LDL cholesterol and triglycerides may have resulted because the subjects were only moderately dyslipidemic. The authors conclude that this study "could not prove that the products used by the patients help avoid cardiovascular disorders; however, it contributed by providing a clearer understanding of how they might assist toward this end."

—Brenda Milot, ELS