15 January 2013

Much has been written regarding the role of soy and breast cancer, but much confusion remains. While research in this area is active, here is what we know:

Soy is an isoflavone, a class of chemical that has weak estrogen-like activity.  We know that women in Asian countries, following a traditional diet, have a lower incidence of breast cancer than women in the US. Their diet consists of large quantities of soy foods starting at a young age. However they eat soy in a natural form – they do not eat “foods” such as soy hot dogs or take soy in supplement form. Research has shown that consuming large quantities of natural soy products starting at a young age seems to confer some estrogen resistance to the breast tissue, which may account for the lower incidence of breast cancer in the Asian population.

So in this country, due to concerns about estrogen and hormone replacement therapy in terms of breast cancer risk, soy supplements are often marketed  as a “natural” remedy for menopausal symptoms that may also reduce a risk of breast cancer, and women consume soy “foods” (such as hot dogs, meat substitutes, and cheese substitutes) thinking that they are helping lower their risk of breast cancer.  Remember that while the traditional Asian diet is high in natural soy products, it is also high in vegetables and low in animal protein and saturated fat. And there is probably more to their lower risk of breast cancer than just diet – a traditional Asian lifestyle is much different from ours in many ways. The development of breast cancer is not a simple cause-and-effect relationship in most cases – it is very complex and the importance of any one specific dietary intervention is difficult to determine.

So regarding menopausal symptoms, my advice is to go as natural as possible, which means soy in organic, whole form (edamame, miso, or tofu), regular exercise, and maintaining a healthy weight. Also do not underestimate the role of yoga, meditation and acupuncture. Anecdotal evidence exists suggesting that in some cases, omega 3’s, evening primrose oil, and black cohash may help but concrete evidence is lacking.

In terms of breast cancer risk reduction, a moderate intake of soy in a whole-food, organic form may actually reduce risk, and research in this area is ongoing.  Avoidance of soy in highly processed “foods” and supplements may be prudent.

Additional Reading / References: