Soy isoflavones could have an effect on bone density, particularly in postmenopausal women. Meta-analyses have found that soy isoflavones increased markers of bone formation in postmenopausal women,[1][2] and a study that followed up with the participants after 3 years of treatment with genistein found that it could improve bone mineral density in osteopenic postmenopausal women.[3] These effects are most pronounced if soy isoflavones are taken earlier in menopause, and the effects are diminished if started later in menopause. There is no substantial evidence that soy isoflavones play a role in bone health in premenopausal women or in men.
While more clinical trials are needed to assess the appropriate timing and dosage and the clinical relevance of the effect soy isoflavones have on bone density, incorporating soy foods into the diet may be worthwhile for perimenopausal and postmenopausal women.[4][5]