Study characteristic:
Ten articles assessed the effect of soy isoflavones (27, 28, 30, 33, 34, 46-48, 51, 55), nine articles assessed the effect of soy isoflavones plus soy protein (24-26, 31, 32, 35, 50, 53, 54), and four articles assessed the effect of both soy isoflavones and soy isoflavones plus soy protein (29, 36, 49, 52). Participants in eight articles received soy isoflavones plus soy protein by taking natural soy product (24-26, 29, 31, 32, 50, 52, 54). Seven articles had two intervention groups and one comparison group (24, 26, 29, 31, 36, 49, 52) and one article had two study groups (25), therefore; we considered every article as two separate articles and separate effect sizes were calculated from each study. In three studies by Llaneza, P et al., (48), Liu Z, M et al., (36), and Aubertin-Leheudre, M et al., (30) CRP concentration reported in regular period during intervention duration, so we calculated separate effect sizes for every treatment duration which CRP concentration was reported. In total, 33 datasets (17 datasets for soy isoflavones and 16 datasets for soy isoflavones plus soy protein) from 19 studies with 1407 subjects were analyzed in our meta-analysis.
Out of twenty-three articles, nine articles had cross-over design (24-27, 35, 46, 50, 53, 54) and fourteen articles had parallel design (28-34, 36, 47-49, 51, 52, 55). Soy isoflavones dose was from 10 mg/day to 160 mg/day and treatment duration ranged from 4 weeks to 96 weeks. Regarding subjects health status, thirteen RCTs indicated soy supplements effects among healthy postmenopausal women (24, 25, 27, 29, 32-35, 49, 50, 52, 53, 55), five RCTs among obese or overweight women (28, 30, 47, 48, 51), one article among postmenopausal women with abdominal obesity (54), two RCTs on postmenopausal women with metabolic syndrome (26, 31), and two articles on patients with diabetes (46) or prediabetes (36).