Phytoestrogens

Phytoestrogens are plant compounds found in soy foods like tofu, tempeh, edamame, and soy milk. Their structure resembles the hormone oestradiol, so they can weakly attach to oestrogen receptors in the body. For years this led to worry that soy might be risky, especially around hormone-sensitive conditions, but the bone research actually tells a more reassuring story.

Randomised trials looking at soy isoflavone supplements in postmenopausal women found modest improvements in bone mineral density and lower markers of bone breakdown. The effect is small, nowhere near what hormone therapy or a bisphosphonate can do, but it moves in a positive direction, and it comes from controlled trials rather than guesswork.

On safety, large studies of people eating soy foods, including breast cancer survivors, have not shown harm, and some show better outcomes. Major cancer organizations now consider moderate dietary soy safe. Concentrated isoflavone supplements are a different matter from whole foods, though, so if you have a history of a hormone-sensitive cancer, it's worth talking with your oncologist specifically about supplements rather than assuming they act the same as tofu or edamame.