A few months ago I was cooking dinner for my boyfriend and me. It consisted of a hefty amount of vegetables and tofu among other delicious things. He’s a lucky man, and I remind him of that every day. While I was cooking, he mentioned that he was concerned about his soy intake. I paused, because even though I knew his concerns weren’t valid. I didn’t know why. I too had heard over and over again that eating too much soy (soy milk, tofu, etc.) could cause men to develop breasts and women, especially post-menopausal women, to develop breast cancer. So naturally I turned towards the human encyclopedia on all things health, my father. He told me that whole soy foods are protective against hormonally driven cancers and that Japanese, who eat them every day from infancy to old age, have some of the lowest rates of prostate and breast cancer in the world. I filed it away under “soy is good”, fed the tofu to my man, and moved on.


Last week the myth of soy foods came back into my life. I had to write a paper for my organic chemistry course (ugh) on a phytochemical relevant to nutrition and integrative health. I chose isoflavones, which, you guessed it, are the estrogen-like components of soy. Isoflavones as weak estrogens, but by blocking hormone receptors on cells, diminish the effects of the body’s own estrogen and reduce risks of certain kinds of cancer. So without further ado I present the fruits of my research labors:


The belief that soy foods are dangerous mostly came from studies done on animals consuming HUGE amounts of soy. This is problematic because lab rats have many physiological and anatomical differences and they metabolize isoflavones differently than we do. There was a story floating around of a man who ate tofu and grew breasts. He was eating more than a pound of tofu a day, which is insane. Even watermelon can be dangerous if you eat an enormous amount of it.


Estrogens are a class of very powerful sex hormones. There are actually a few different types of estrogen and their main purpose is to tell cells to grow. Think stimulating your menstrual cycle, and growing endometrial cells in pregnancy. The faster cells multiply, the greater the chance they will undergo malignant transformation (turn into cancer cells). So it’s pretty understandable why scientists and nutritionists freaked out about isoflavones. The thing is, isoflavones don’t actually duplicate the effects of estrogen. Isoflavones are chemically similar to estrogen (which is what the hub bub was about). So they can bind to estrogen-receptors and have estrogen-like effects on the body under certain conditions. But isoflavones bind to receptors in unique ways, causing different and even opposite physiological effects. This is why isoflavones can protect us from breast and prostate cancer as well as reduce the frequency of menopausal hot flashes and improve renal function- all really great things am I right?


Europe recently decided to conduct a huge study on isoflavones to figure out once and for all if they are dangerous. Guess what they found? NO. The European Food Safety Authority determined that isoflavones do not negatively impact the breast or other organs.


Phew! Tofu lovers around the world can breathe easy.


So what do you think about soy? Were you a believer that tofu was bad for you? Let me know in the comments below!