Thank you for posting. For years I've been wondering about this and this makes things a bit easier to understand, if indeed the animal studies can be translated to humans.

The way I'm reading it is if you ate soy for years and then had a b.c. dx, it's okay to eat some soy afterward. Since I was vegan and then vegetarian for years, and ate tofu and some soy meatless products from time to time, I'm discerning that eating soy from time to time now probably won't hurt me, if the studies are to be trusted and can be translated to human consumption.

Yes? No?

I'm glad to see this study, even if at this point it is just based on rats. What this study does is pull together and support the findings from a number of earlier studies.

• Quite a few previous studies, mostly done among Asian populations, that have found that women who consume significant amounts of soy starting in childhood or adolescence tend to have lower breast cancer rates as adults.

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• There have also been a number of studies, mostly lab and/or mouse/rat but some based on humans in Western countries (i.e. women who have Western and not Asian diets), that have shown that soy consumption after an ER+ breast cancer diagnosis increases recurrence risk. It was these types of studies that led many of us, myself included, to be told that we should minimize our soy consumption after we'd been diagnosed.

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For years people thought that the results from these two different types of studies was inconsistent, and there has been a lot of discussion (including on this site) to suggest that the first group of studies (which show a benefit to soy) negate the second group of studies (which show possible harm to those who have been diagnosed with an ER+ breast cancer). I never saw an inconsistency in the results. Here are a couple of old posts of mine, the first from June 2007 and the second from January 2009:

"There has been one study (and maybe more) that suggests that if teenage girls and young women eat soy, it may reduce their future risk of breast cancer. This is far from being proven, but the soy industry, and the health food industry who are so gung-ho on soy, have taken this to mean that "soy reduces breast cancer". But an adolescent consuming soy is a totally different situation than a women who's had estrogen-driven breast cancer consuming soy. Although these studies aren't 100% conclusive either, the indication is that soy, being a phytoestrogen, is harmful to women who've had breast cancer."

"I think one of the problems we have to consider is that the dietary rules may be different if you are trying to prevent breast cancer vs. if you've had it. From my understanding, studies have shown that soy can be effective at reducing the occurrence of breast cancer and as a result, it's advised that young girls start consuming soy and continue through adulthood. Similarly, women in Asian countries who consume soy starting in childhood have lower breast cancer rates. But, if soy has not been part of your diet since childhood and/or if you have an ER+ breast cancer, soy may be problematic in the way in which it adds estrogen into your system and how that estrogen acts. It appears that how soy reacts in our systems may be different if it's a lifelong habit vs. if it's a new or infrequent habit. And it may be different if we are pre-menopausal vs. if we are postmenopausal."

Nice to see a study that confirms what I've been saying for all these years!

Now we need more information to understand what level of previous soy consumption, and starting at what point in life, makes a difference to one's post-diagnosis risk. I never consumed soy as a child or adolescent, but I consumed a lot of soy in the 10 years before I was diagnosed. Did I consume enough soy, and early enough, that soy would have been beneficial to me after my ER+ diagnosis? Or did I start too late and would a continuation of my soy consumption have increased my recurrence risk? And what about those 10 years of soy consumption, started well into adulthood? Harmful, possibly fueling my BC development, or helpful, possibly reducing my BC risk? The problem with the nuanced findings from this study is that it just leads to more questions!

This was also my concern, since Asians start soy/tofu from birth---I added it as a young adult. I wonder if that was more hurt than help and maybe contributed to my breast cancer? Or did it make it less aggressive ? or who knows. And I do wonder how valuable a rat study is when extrapolated to humans.

I wouldn't buy soy from either Asia or our big ag.http://www.vermontsoy.com/