Effect of whole soy and isoflavones daidzein on bone turnover and inflammatory markers: a 6-month double-blind, randomized controlled trial in Chinese postmenopausal women who are equol producers

Six-month double-blind randomized controlled trial in Chinese postmenopausal women aged 45-71 years who were equol producers, with pre- or stage 1 hypertension. Participants were recruited from local communities or health centers in China. Two active arms were analyzed: whole soy (N=90) and daidzein (N=90), alongside a placebo group.

Whole soy arm: 40 g soy flour daily as a solid beverage for 6 months, providing 12.8 g protein and 49.8 mg total isoflavones (23.2 mg daidzein and 19.4 mg genistein, aglycone equivalents), mixed with 300 ml water or beverage. Daidzein arm: 40 g low-fat milk powder plus 63 mg daidzein daily for 6 months, also mixed with 300 ml water or beverage. A low-fat milk powder placebo was used as the comparator.

Overall, whole soy and daidzein did not meaningfully improve bone turnover or most inflammatory markers in equol-producing Chinese postmenopausal women. Across groups, changes in the main bone markers were not significant for β-CTX (p=0.632), PINP (p=0.458), BALP (p=0.362), OST (change p=0.228), or 25(OH)D3 (change p=0.684). Inflammatory markers were also generally unchanged for IL-6, TNF-α, homocysteine, and transferrin. The main exception was hs-CRP, which decreased in the whole soy group (1.747 ± 2.041 to 1.411 ± 1.963; change p=0.022), while the daidzein group increased (1.260 ± 1.155 to 2.011 ± 3.262).

The trial was limited to a specific subgroup of equol-producing Chinese postmenopausal women with pre- or stage 1 hypertension, which limits generalizability. The intervention lasted 6 months, which may be too short to detect clinically important skeletal effects. Some outcome reporting is incomplete for comparing all arms, and adverse events/compliance were reported elsewhere rather than in the extracted text.