Just soya know

Di­eti­tian Laura Tilt digs deeper than the head­lines to re­veal the truth be­hind those soy scare sto­ries

Women's Health Australia - - NEWS - WH

We dig into the de­bate on the hum­ble soy bean – di­etary vic­tim or vil­lain?

FFS. Tofu? How can tofu be bad for you? I get it. Just when you think you’ve knocked the dairy de­bate on its head, scary soy claims make you want to throw out the con­tents of your freshly stocked fridge. Sales of soy have soared in re­cent years, but it’s of­ten suf­fered bad press, with stud­ies link­ing fe­male con­sump­tion of soy to breast cancer and even in­fer­til­ity. Yikes!

So, where do these fears stem from? Glad you asked. Most are linked to the nat­u­rally oc­cur­ring phy­toe­stro­gens (hor­mone-like plant com­pounds) in soy, known as isoflavones. Phy­toe­stro­gens mimic the ef­fects of oe­stro­gen in the body, lead­ing to con­cerns that soy may be harm­ful due to a link be­tween high oe­stro­gen lev­els and health risks, in­clud­ing breast cancer – oe­stro­gen in­creases cell di­vi­sion and may there­fore con­trib­ute to the growth of cancerous cells.

But the plot thick­ens. In a 2008 study pub­lished in the Bri­tish Jour­nal of Cancer, re­searchers found breast cancer risk was sig­nif­i­cantly re­duced in women con­sum­ing high amounts of soy (pro­vid­ing more than 10mg isoflavones), com­pared with those eat­ing smaller amounts. Quite the turn­around. The sci­ence be­hind it? In short, this can be ex­plained by the pres­ence of two oe­stro­gen re­cep­tors in the hu­man body – al­pha and beta. When it comes to breast cancer, al­pha poses the big­gest risk. Ac­cord­ing to ex­perts, these isoflavones pref­er­en­tially bind to the beta re­cep­tor, which may ac­tu­ally have a pro­tec­tive ef­fect.

Cancer risk aside, a quick google of ‘soy’ and ‘fer­til­ity’ is enough to make you ditch the soy lat­tes for good. It comes down to the link be­tween genis­tein (the pri­mary isoflavone in soy) and re­duced fer­til­ity in stud­ies done on sheep, mice and rats. The good news? These stud­ies typ­i­cally in­volved con­sum­ing genis­tein at lev­els five times higher than those you’re ex­posed to by eat­ing food con­tain­ing soy, so there’s an el­e­ment of scare­mon­ger­ing here.

In fact, more re­cent re­search sug­gests soy might ac­tu­ally be good for fer­til­ity. In a 2015 Amer­i­can So­ci­ety for Re­pro­duc­tive Medicine study of women un­der­go­ing fer­til­ity treat­ment, isoflavone in­take was pos­i­tively linked with live birth rates. And, ac­cord­ing to a 2016 study in Nu­tri­ents, soy isoflavones may even pro­tect against the neg­a­tive ef­fects of BPA (the chem­i­cal found in plas­tic and cans) on fer­til­ity.

The up­shot? There just isn’t enough con­vinc­ing ev­i­dence in hu­man tri­als to sug­gest you need to ditch soy. (High fives all round!) When it comes to fer­til­ity, there are ar­guably more im­pact­ful things to con­sider; car­ry­ing too much or too lit­tle body fat, smok­ing, booze and high stress lev­els can all neg­a­tively af­fect your baby-mak­ing chances. Also, eat­ing soy pro­tein as part of a healthy diet has been linked with a lower risk of heart dis­ease, which is yet another rea­son not to ditch it. Edamame me up, baby!

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