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  • Writer's pictureHelen

Is soya good for women?

Updated: Sep 27, 2022

Soy foods are rich in nutrients including B vitamins, fibre, potassium, magnesium, and high-quality protein. Unlike some plant proteins, soy protein is considered a complete protein.

The controversy around soya comes down to its uniquely high content of isoflavones (a type of plant estrogen – phytoestrogen). These compounds have oestrogenic properties, which means they act like oestrogen, the primary female sex hormone, and bind to oestrogen receptors in the body – and oestrogen can fuel the growth of some types of breast cancer.

But while scientists have extensively researched the compound’s effects in the body over the last few decades, the answer about whether isoflavones themselves can contribute to cancer risk isn’t straightforward. And often, it seems soya protects against cancer risk – rather than making it worse.

High soya intake among women in Asian countries has been linked to their 30% lower risk of developing breast cancer compared to US women, who eat much less soya. (The average person’s intake of isoflavones in Japan, for example, is between 30 and 50mg, compared to less than 3mg in Europe and the US.)

One reason there isn’t a more definitive answer is because isoflavone either acts like oestrogen in the body, or its opposite. When we eat soya, isoflavone either binds to the alpha oestrogen receptor in the body, which stimulates a tumour’s growth rate, or the beta receptor, which decreases growth rate and induces apoptosis.

"Isoflavone prefers to bind to beta receptors", says Bruce Trock, professor of epidemiology and oncology at Johns Hopkins School of Medicine in Maryland in the US. "That makes it more likely to reduce potential cancer risk".

Soya’s benefits also depend on the type we consume. Isoflavone content varies in unprocessed soybeans, such as edamame beans, compared to processed soya foods – and the closer the food is to the soyabean, the higher its isoflavone levels. Edamame has around 18mg of isoflavones per 100g, while soya milk has between 0.7 and 11mg.

“The only thing we can say is that women should be safe to consume soya foods in amounts consistent with Asian diet, including tofu, fermented soya foods and soymilk, but studies show that the more soya is processed, the lower the level of isoflavones, which we think are protective elements,” says Trock.

As women get to perimenopause or the menopause their levels of oestrogen drop so soya and other phytoestrogen rich foods (like beans, lentils and chickpeas) may be beneficial. Dr Marilyn Glenville suggets eating one serving of isoflavone-rich food daily ( about 55g), to give around 40g of isoflavones.

Steer clear of soya protein isolates (highly refined forms of soya). Always eat it in its natural form, such as miso, tofu, edamame beans and organic soya milks made from whole beans.

Try this Healthy Green Bowl, recipe that uses miso paste (fermented soy) and is super healthy and quick to make.


Dr Marilyn Glenville - The Natural Health Bible for Women


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