Phytoestrogens — from soy, flaxseed, and red clover — are among the most debated tools in perimenopause. A 2025 meta-analysis found soy isoflavones significantly improved mood, palpitations, and headaches, though hot flush effects were less consistent. Flaxseed lignans showed benefit in a randomised trial. Whether they work depends on your gut bacteria. Here's the honest evidence — including the breast cancer safety question most articles dodge.