Demystifying the Relationship Between Soy and Breast Cancer

Cactus Bloom © lynette sheppard

Cactus Bloom © lynette sheppard

Mary Tagliaferri MD shared this plain talk guest post with us. I had the pleasure of interviewing “Dr. Tags” recently – and found a new goddess sister! As an MD with a Master’s in Oriental Medicine, she bridges the gulf between Eastern and Western medicine approaches. Most important, she has conducted research for the last 20 odd years on plant based natural remedies. You can find her Menopause formula on her website: She sent me some to try – and now I don’t know how I got by without it. Enjoy her special brand of wisdom here:

Demystifying the Relationship Between Soy and Breast Cancer

Women with a history of breast cancer often asked me if it’s safe to eat soy products. Soy products include simple soybeans (edamame), or manufactured forms such as miso soup, tempeh and tofu.  Some breast cancer specialists tell their patients to avoid soy products since they’re “estrogenic,” meaning they contain estrogens. A woman’s breast cancer may be of the estrogen-responsive type, meaning that estrogen “docks” on the tumor cells and causes breast tumor growth.  The estrogen in soy is a phyto-estrogen (phyto means plant-based). Phytoestrogens can sometimes act as estrogens in our bodies, but they do not stimulate breast cancer associated tumor.

I’m always amazed when I hear that medical professionals continue to be confused on this topic. Most physicians work very hard to keep abreast of the latest medical findings, but somehow the “soy issue” slips through the educational cracks.

What we know about soy from other cultures

Japanese women have one-third the amount of breast cancer when compared to American women. However, when Japanese women move to the US, the first generation of their offspring has the same rate of breast cancer as American women!  Since a person’s genetic lineage can’t change within one generation (with very rare exceptions in the form of mutations), that leaves the person’s environment at cause.  The Western diet, a culprit in so many “diseases of affluence” (diseases prevalent in First World countries), is again partly to blame for the phenomenon. Thanks to our American appetites, we now have a 1 in 8 lifetime risk for breast cancer, and the disease is the second leading cause of cancer death.

When I had breast cancer at the young age of 30, I was a die-hard tofu fan.  I wanted to know if I would be able to continue eating a staple of my diet and started digging into the medical literature. My research led me to write a chapter about soy in Breast Cancer: Beyond Convention, a book I edited about complementary and alternative practices in the treatment of breast cancer.

What I’d found was this:

Soy intake in an amount consistent with a traditional Japanese diet (2-3 servings daily, containing 25-50 mg isoflavones) has been shown to be protective against breast cancer and breast cancer recurrence.
Soy does not increase circulating estrogen levels in the body or affect estrogen-responsive tumor tissues.
Women with a history of breast cancer who are taking tamoxifen and eating soy do not have an increased risk of breast cancer recurrence.

How not to eat soy

The temptation in our American culture is to take a food known to have healthful properties, process it into high-dose pills, and pop a few of those capsules when we feel like we need a boost. We’ve done it with fish oil, red wine antioxidants, mushrooms, garlic, and so on. Sometimes this approach works, when done in a measured and thoughtful way (think of the complex and ingenious combinations of herbs in Traditional Chinese Medicine formulas). Most of the time, though, we overdose on one specific chemical compound in that food, without really knowing how it will affect us in the long run. I would caution anyone (not just breast cancer patients or survivors) against the use of high-dose soy supplements, since large amounts of soy phytoestrogens could be unsafe.

How to enjoy your soy

Have those 2-3 servings daily, since they’ve been shown not to cause harm and to possibly be protective against breast cancer development and breast cancer recurrence. Cultivated or fermented soy products like miso paste and tempeh may be easier to digest than plain soybeans or tofu. If you’re currently undergoing treatment for breast cancer, please discuss any soy use with your doctor first.

Enjoy your soy, eat it with peace of mind, knowing that it can be a part of a healthy diet before and after breast cancer.

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2 Responses to Demystifying the Relationship Between Soy and Breast Cancer

  1. Barbara Morris November 29, 2014 at 5:16 pm #

    Hi Lynette,

    I just wanted to give you some feedback regarding Dr Tags’ product. I tried it and at first it worked very well for me in reducing and nearly eliminating hot flashes. However, I am quite disappointed in their customer service. I was scheduled for some minor surgery and I tried contacting the company to ask if their menopause supplement contraindicated for surgery. I know there are several herbal remedies, along with certain vitamins etc that we are told to discontinue before surgery. I got absolutely no response from them. I then tried sending them a message through their facebook page and still got no response. I went ahead and stopped taking the supplement 2 weeks before surgery just to be safe. But ever since I began taking the supplements again, they are not working very well. Don’t know if it’s a difference in the batch that was processed, or something else. However, I decided not to reorder and go back to black cohosh.

    Sorry for the long comment, but I did want to let you know about my experience, since you promote Dr Tags and her products.

  2. LynetteSh December 7, 2014 at 2:08 pm #

    Wow, Barbara, so sorry to hear that. I will try to get hold of Dr. Tags and find out more (I’ve talked with her on the phone and she was always so delightfully present and accomodating. Stay tuned.

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