Why do phytoestrogens help some people but not others? It might come down to the unique mix of bacteria in your gut, which can change how your body uses these plant compounds.

What we've found so far is that gut bacteria may play a role in how phytoestrogens work in the body. The evidence we've reviewed leans toward the idea that differences in gut bacteria could help explain why these plant compounds affect people differently [1]. Our analysis of the available research shows that the unique mix of microbes in a person’s gut might influence how their body processes phytoestrogens [1]. These plant compounds, found in foods like soy and flaxseeds, can have estrogen-like effects, but not everyone responds to them in the same way. One reason for this variation could be that certain gut bacteria are able to transform phytoestrogens into more active forms, while others may not [1]. This means that two people eating the same amount of soy might have very different experiences, based on their gut microbiome. So far, we’ve only reviewed one claim on this topic, and it supports the idea that gut bacteria affect phytoestrogen activity [1]. There are no studies in our current analysis that refute this idea, but the total number of studies is very limited. Because of this, we can’t say how strong or consistent this effect might be across different people or diets. Our current analysis doesn’t allow us to draw firm conclusions, but it does suggest a possible link worth considering. We recognize that our understanding is still developing, and future evidence could change how we see this relationship. Practical takeaway: The bacteria in your gut might influence how your body uses plant-based estrogens, so what works for one person may not work the same for you — and your gut bugs could be part of the reason why.