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What's Wrong With Soya?


Soya. It’s a controversial story. While the health benefits of soya consumption have been shouted from the rooftops for many years now, there are also frequent reports that it may actually be bad for your health. The pro-soya view tells us that this wonder-food will reduce your risk of breast and prostate cancer, strengthen your bones, ease menopausal symptoms, prevent heart disease, is an excellent ‘hypoallergenic’ alternative to cow’s milk and a perfect protein source for vegetarians and vegans. On the other hand, we hear that soya may actually contribute to the development of hormone-linked cancers of the breast and prostate, that it may suppress thyroid function, reduce fertility in men and affect the sexual and mental development of children. Also, that that its allergic potential could be significant and serious. So, what’s the truth? Let’s look at the facts.

Hormone Helper or Disruptor?
Claims have long been made that the phytoestrogens present in soya have hormone balancing properties. Phytoestrogens are naturally occurring oestrogen-like ‘chemicals’ estimated to be anywhere between 50 and 20,000 times weaker than natural oestrogen. If a woman is actually low in oestrogen, such as during the menopause, the weak oestrogenic effect of phytoestrogens can help to relieve menopausal symptoms. However, in cases of oestrogen excess – which can occur as a result of taking the contraceptive pill, HRT, from environmental exposure or simply from inadequate breakdown of natural oestrogen – these weak phytoestrogens actually reduce the oestrogenic effect by docking onto the oestrogen receptor sites, so blocking the stronger oestrogens.

There have been a number of negative reports of the effects of soya ‘isoflavones’ (the most active type of phytoestrogen) on fertility in animals, including a case of tropical birds in New Zealand. The breeders began feeding their birds a new soya-based feed. The ensuing years saw decreased fertility, early sexual maturation, deformed, stunted and stillborn chicks, aggressive behaviour and severe digestive problems. After changing to a non-soya feed all of these problems went away. Stories such as this have led people to believe that soya might be harmful to hormonal health. Dr Margaret Ritchie, an expert in phyoestrogens at the University of St Andrews, is quick to point out that different animal species metabolise isoflavones differently. Even the rat, the animal used for most of the research trials into soya, handles soya very differently from humans.