Gardner C D, Newell K A, Cherin R, Haskell W L
Stanford Center for Research in Disease Prevention and the Department of Medicine, Stanford University Medical School, Stanford, CA, USA.
Am J Clin Nutr. 2001 Apr;73(4):728-35. doi: 10.1093/ajcn/73.4.728.
Clinical trial data and the results of a meta-analysis suggest a hypocholesterolemic effect of soy protein. The effect may be partially attributable to the isoflavones in soy. Few studies have examined the separate effects of soy protein and isoflavones.
The objective of this study was to determine the effect of soy protein and isoflavones on plasma lipid concentrations in postmenopausal, moderately hypercholesterolemic women.
This was a randomized, double-blind, placebo-controlled clinical trial with 3 treatment groups. After a 4-wk run-in phase during which the women consumed a milk protein supplement, the subjects were randomly assigned to 12 wk of dietary protein supplementation (42 g/d) with either a milk protein (Milk group) or 1 of 2 soy proteins containing either trace amounts of isoflavones (Soy- group) or 80 mg aglycone isoflavones (Soy+ group).
LDL-cholesterol concentrations decreased more in the Soy+ group (n = 31) than in the Soy- group (n = 33) (0.38 compared with 0.09 mmol/L; P = 0.005), but neither of these changes was significantly different from the 0.26-mmol/L decrease observed in the Milk group (n = 30). The results for total cholesterol were similar to those for LDL cholesterol. There were no significant differences in HDL-cholesterol or triacylglycerol concentrations between the 3 groups.
The difference in total- and LDL-cholesterol lowering between the 2 soy-protein supplements suggests an effect attributable to the isoflavone-containing fraction. However, the unexpected LDL-cholesterol lowering observed in the Milk group, and the fact that there was no significant difference between either soy group and the Milk group, suggests that changes may have been due to other factors related to participation in the study.
临床试验数据和一项荟萃分析的结果表明大豆蛋白具有降胆固醇作用。这种作用可能部分归因于大豆中的异黄酮。很少有研究考察大豆蛋白和异黄酮各自的作用。
本研究的目的是确定大豆蛋白和异黄酮对绝经后、中度高胆固醇血症女性血浆脂质浓度的影响。
这是一项随机、双盲、安慰剂对照的临床试验，有3个治疗组。在为期4周的导入期内，女性食用乳蛋白补充剂，之后将受试者随机分配至3组，进行为期12周的膳食蛋白补充（42克/天），分别给予乳蛋白（乳蛋白组）或两种大豆蛋白之一，其中一种含微量异黄酮（大豆-组），另一种含80毫克苷元异黄酮（大豆+组）。
大豆+组（n = 31）的低密度脂蛋白胆固醇浓度下降幅度大于大豆-组（n = 33）（分别为0.38毫摩尔/升和0.09毫摩尔/升；P = 0.005），但这两组的变化与乳蛋白组（n = 30）观察到的0.26毫摩尔/升的下降幅度均无显著差异。总胆固醇的结果与低密度脂蛋白胆固醇相似。3组之间高密度脂蛋白胆固醇或三酰甘油浓度无显著差异。
两种大豆蛋白补充剂在降低总胆固醇和低密度脂蛋白胆固醇方面的差异表明，这种作用归因于含异黄酮部分。然而，乳蛋白组出现意外的低密度脂蛋白胆固醇降低，且大豆组与乳蛋白组之间无显著差异，这表明这些变化可能是由于参与研究的其他相关因素所致。
