For many vegans, soy products including tofu and tempeh make for popular, tasty alternatives to meat. But if what we hear through the edamame vine is true about their effects on our hormones, the question “should vegans avoid soy?” is one that many have asked themselves as their plant-based diet evolves.
This all comes down to a perception that’s been spread of soy causing hormone disruption, feeding the problem of excessive oestrogen linked to conditions like polycystic ovary syndrome and breast cancer.
In reality, studies have shown that the countries which consume most soy are some of the healthiest on the planet. The misconception can be traced to soy’s natural phytoestrogens (phyto = plant) called isoflavones. Where those who believe these phytoestrogens are more harmful than the oestrogens in animal products are wrong is phytoestrogens actually occupy the receptor sites on tissues that real oestrogen which drives cancer growth would otherwise lock onto, so they can actually be seen as having an anti-carcinogenic effect.
The body contains two types of oestrogen receptors: alpha and beta. Your own natural oestrogen prefers alpha-receptors, whilst plant oestrogen has an affinity for beta. The effects of soy phytoestrogens on different tissues depends on the ratio of both receptors.
Oestregen has positive effects in some tissues and potentially negative ones in others. For example, high oestrogen can be good for the bones, but can increase the likelihood of developing breast cancer. In an ideal world, you’d have a selective oestrogen receptor modulator in your body that would have pro-estrogenic effects in some tissues and anti-estrogenic effects in others. And that’s what soy phytoestrogens appear to be.
Which is to say that it’s more advisable to look out for mammalian oestrogen in meat and dairy, rather than phytoestrogen. Phytoestrogens dock onto the same receptors as your own oestrogen, but have a weaker effect, so can act to block the effects of more powerful animal oestrogen.
One word of caution when you do consume soy products, though – be sure to choose traditional forms like tofu, tempeh, edamame and natto, rather than non-organic, GMO types such as the isolated soy protein found in a number of vegan protein supplements.