Let's Talk Soy and CancerAs an integrative oncology dietitian, I need to address the topic of soy and cancer. There is a lot of really pertinent discussion to be had about soy and GMOs, thyroid, phytic acid, protease inhibition, and processing but I'm not talking about those things here. Note this post is specifically about soy and cancer. Let me know if you want more info on any of those topics and I can address them in the future. I'm talking specifically here about all the people who tell me daily: "but you know, soy is really bad for cancer patients" or "my doctor told me not to eat it" or "I'm scared of soy" or "soy causes breast cancer". Let's discuss!
The History and ScienceI'm not necessarily advising you here to go out and start eating a lot of soy...more, I want to clear up some confusion about it's connection with cancer and reduce patient fear on the subject. Whether you can interpret the actual research, Dr. Oz is your nutrition guru, you are addicted to the NY Times, or individual doctors or medical facilities are your most trusted resource, I hope you take the time to look through the variety of expert opinions below and start to understand that the fear of soy and breast cancer is based on OLD research founded on animal studies. Animals (rats and mice namely), metabolize estrogen differently than humans do. Human estrogen can fuel some types of breast cancer. Because soy has plant estrogens or "phytoestrogen", people are afraid it will mimic human estrogen when consumed. (See the chemical structures of plant and human estrogen below):
Myth bust! Hundreds of plants have phytoestrogens, including many grains and vegetables. It's a normal part of plants and we all eat these compounds every day. Phytoestrogens can be beneficial, fitting into human estrogen receptors (they mimic each other in structure) but blocking the receptor from being stimulated by human estrogen. That's right - BLOCK the receptor...in a good way. You know what mimics human estrogen much more than plant estrogen and can actually be stimulating to these receptors? Animal estrogen. In my study of the literature, soy has never been shown to cause cancer in human studies - there is no proven direct correlation between the two. Available research does show a protective effect against cancer, benefit in preventing cancer recurrences, and sometimes is has shown neutral findings (neither good or bad for cancer).
Next time you find someone trying to tell you that soy causes breast cancer or that is unsafe for cancer patients, feel free to share any of these resources or tell them your Registered Dietitian Ginger Hultin says not only is it ok to eat organic soy in whole food form (tofu, tempeh, miso, edemame) but may also be healthful for cancer patients and survivors as well as prevention of cancer incidence.
Here's my list of resources that say soy is safe:
Research:Hopefully all other sources are based on the actual, recent, well-designed research. There is a lot out there, but here are some links to studies that I like and use in my educations. I focused here on meta-analysis to capture a broader range of individual studies instead of listing all of those out. I also tried to choose very recent pieces.
Soy food intake after diagnosis of breast cancer and survival: an in-depth analysis of combined evidence from cohort studies of US and Chinese women
Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: a meta-analysis of epidemiological studies.
Meta-analysis of soy intake and breast cancer risk.
The Effects of Soy Consumption before Diagnosis on Breast Cancer Survival: the Multiethnic Cohort Study
News:Sometimes I like referencing news articles because journalists tend to do their research well, consult with experts, and will be ripped apart by the public if they present false information. Pick your favorite below; I like the NY Times article that came out late last year:
New York Times: Is it Safe to Eat Soy?
Really? The Claim - Eating Soy Increases the Risk of Breast Cancer
CNN: Get Smart About Soy
Washington post: Eat Your Soy, Boy
Huffington Post: 5 Myths About Soy You Probably Still Believe
These guys need to stay up to date with the most current research which drives their treatments and recommendations to patients. There are a lot of options in this category, and they're all basically saying the same thing:MD Anderson: Do soy foods increase cancer risk?
Dana Farber: Is eating soy safe for breast cancer patients and survivors?
Block Center for Integrative Cancer Care: Breast Cancer Awareness Month: boosting survival
Fred Hutchinson: Soy: is it safe for cancer survivors?
American Cancer Society: The Bottom Line on Soy and Breast Cancer Risk
National Cancer Institute: Nutrition Issues--Soy
Some other Favorites of Mine:Here are some other resources you might find interesting and well written. Dr. Oz is in here because my patients typically get behind whatever he says - and he says organic, unprocessed soy is safe! He also features Registered Dietitians as his experts, so you know he's partnering with educated folks.
Harvard Health: Straight Talk About Soy
Linus Pauling Institute at Oregon State University: Soy Isoflavones
Today's Dietitian: Soyfoods and Cancer
Dr. Oz: Soy: the good, the bad and the best
Which Soy Products are best (with Ashley Koff RD!)
*Disclaimer - I can't possibly list all sources that support my point here. If you want more info in any category, just let me know and I'm happy to provide. These are just samplings from a diverse array of sources people tend to trust.