Phytoestrogens, plant-derived compounds with estrogen-like activity, have been explored as a therapy for premenstrual syndrome (PMS) due to their potential to modulate hormonal fluctuations. The rationale is based on their structural similarity to endogenous estrogens, allowing them to bind to estrogen receptors and exert weak estrogenic or anti-estrogenic effects depending on endogenous hormone levels. Some traditional medicine systems have used phytoestrogen-rich plants to address female reproductive concerns, but the majority of evidence for PMS management comes from modern clinical interest rather than long-standing traditional use.

Scientifically, the evidence supporting phytoestrogens for PMS is limited and mixed. A few small randomized controlled trials and observational studies have investigated isoflavones (such as those from soy) or lignans (from flaxseed) for PMS symptom relief. Results have shown mild improvements in symptoms like breast tenderness and mood swings in some studies, but others found no significant benefit compared to placebo. Systematic reviews and meta-analyses conclude that while phytoestrogens may have a biological basis for effect, robust, high-quality clinical data are lacking. Major guidelines do not currently endorse phytoestrogens for PMS due to insufficient evidence. In summary, the scientific justification exists but is weak (evidence rating: 2/5), and more rigorous studies are needed to clarify their role.