Indication: Cardiovascular disease

Source: Am J Clin Nutr, February, 2006;

83(2):244-51.

Research: Previous research supports a role for soy protein in reducing serum lipids; however, few studies involved healthy male subjects or focused on soy isoflavones (or did both). The objective of this study was to ascertain the effects of soy protein varying in isoflavone content on serum lipids in healthy young men. Thirty-five males in their 20’s and 30’s consumed either a milk protein isolate (MPI), low-isoflavone soy protein isolate (low-iso SPI; 1.64 +/- 0.19 mg aglycone isoflavones per day), or a high-isoflavone SPI (high-iso SPI; 61.7 +/- 7.4 mg aglycone isoflavones per day) for 57 days each, separated by four-week washout periods, in a randomized cross-over design. Blood samples were collected at the beginning and end of each treatment period, and total, LDL and HDL cholesterol; triacylglycerols; apolipoprotein (apo) B; apo A-I; and C-reactive protein (CRP) were measured in serum. Twenty-four hour urine samples were collected for three consecutive days at the end of each treatment period and analyzed for isoflavones.

Results: Urinary isoflavones were significantly greater with consumption of the high-iso SPI than with that of the low-iso SPI or MPI. The differences between the three treatments with respect to individual serum lip-ids were not significant, but the ratios of total to HDL cholesterol, LDL to HDL cholesterol, and apo B to apo A-I were significantly lower with both SPI treatments than with MPI treatment. Therefore, researchers concluded that soy protein, regardless of iso-flavone content, modulates serum lip-id ratios in a direction beneficial for cardiovascular disease risk in healthy young men.