Doctor's Note

For more on breast cancer risk, check out these videos:
Can Flax Seeds Help Prevent Breast Cancer?
BRCA Breast Cancer Genes and Soy
Breast Cancer and Constipation
Cholesterol Feeds Breast Cancer Cells
Statin Cholesterol Drugs and Invasive Breast Cancer

And check out my other videos on breast cancer

For more context, also see my associated blog posts: Breast Cancer and DietSoy and breast cancer: an update; and Soy milk: shake it up! 

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  • This is what I am curious about. Does soy lower estradiol and estrone? Or does it act more like DIM and work for a better balance. Isn’t estradiol heart protective, helping memory, blood sugar, etc……while estrone makes ya gain weight, etc…..?? I thought that you wanted the estradiol to be at least twice that of the estrone. If soy increases estradiol then I will Throw a party. And isn’t bioidentical estrogen made from soy, I mean prescription estrogen that is not made from a drug company. So in that case, the soy is used to boost estrogen, but the happy estrogen. I go back and forth on soy because I don’t really understand what it does to the sex hormones and the LAST thing I want to do is to lower my happy estrogen. I do have to say that we cooked two pounds of tofu after the video that soy made ya skinny. :)

  • What’s up with the studies citing negative effects of soy? There is a lot of media out there on Dr. Mercola – which says that soy is terrible for you. Really. A bean?

    • DrDons

      I know of no good scientific articles on the adverse effects of soy. Looking into Dr. Mercola’s background and claims should be enough to avoid following his recommendations.

    • Crush Zion

      Sure, there’s no such thing as a dangerous bean! Have yourself some raw kidney beans (esp. sprouted). :)

  • Kelleymac

    Oh ya.. Because a two min video says so your all gaga over it. Sorry im not buying it. Where is your proof!

    • Thule

      Err… didn’t you notice that just below the video there is a section with Sources Cited? (with links to the studies)

      Everything presented is based on studies. In this case:

      A. Lee, X. O. Shu, H. Li, G. Yang, H. Cai, W. Wen, B. T. Ji, J. Gao, Y.
      T. Gao, and W. Zheng. Adolescent and adult soy food intake and breast
      cancer risk: Results from the shanghai women’s health study. Am. J.
      Clin. Nutr., 89(6):1920-1926, 2009.

      L. A. Korde, A. H. Wu, T. Fears, A. M. Y. Nomura, D. W. West, L. N.
      Kolonel, M. C. Pike, R. N. Hoover, and R. G. Ziegler. Childhood soy
      intake and breast cancer risk in Asian American women. Cancer
      Epidemiology Biomarkers & Prevention, 18(4):1050, 2009.

      B.N. Fink, S.E. Steck, M.S. Wolff, J.A. Britton, G.C. Kabat, M.M.
      Gaudet, P.E. Abrahamson, P. Bell, J.C. Schroeder, S.L. Teitelbaum, A.I.
      Neugut, & M.D. Gammon. Dietary flavonoid intake and breast cancer
      survival among women on Long Island. Cancer Epidemiol Biomarkers Prev,
      16(11):2285-2292, 2007.

      N. Guha, M. L. Kwan, C. P. Quesenberry Jr, E. K. Weltzien, A. L.
      Castillo, and B. J. Caan. Soy isoavones and risk of cancer recurrence in
      a cohort of breast cancer survivors: The life after cancer epidemiology
      study. Breast Cancer Res. Treat., 118(2):395-405, 2009.


    I am well confused about eating soya when having a cancer….i have found many articles which suggest that eating soya reduces the risk of cancer coming back and increases survival rate etc…but there is also the whole lot of articles uploaded recently that suggest that although soya can reduce the risk of getting a cancer it is not recomender for people who already have one becuase of that thingy similar to estrogen…my mum has breast cancer…should she avoid soya or should she start eating it???

  • DrDons

    The early confusion has been answered by more recent studies. The current science supports the use of soy in the diet of patients who have had breast cancer. Other videos you might find of interest is the effects of exercise on breast cancer: and specific vegetables on breast cancer: & Animal and epidemiology studies support avoiding the consumption of animal protein in patients with cancer.

  • Michael Greger M.D.

    Also be sure to check out my associated blog post Breast Cancer and Diet!

  • Angie

    What about the concern over soy and endometrial cancer when taking tamoxifen?

    • Joseph Gonzales R.D.

      I wrote a post about soy Should I stay away from soy if I have breast cancer? Although I do not touch on endometrial cancer tamoxifen is often prescribed. Ask your doctor when the best time to take your medication is if eating soy foods. There is no data to suggest whole soy foods cannot be consumed if you have endometrial cancer or you take tamoxifen. A great link by oncology RDs can be found here. Hope this helps!

  • ahimsasoulx

    Hi Dr Greger, what are your thoughts on Dr Russell Blaylock’s studies on Soy and Glutamate?

  • saliminus

    A friend was diagnosed with breast cancer recently and is undergoing conventional treatment, however with my advice is also trying her best to eliminate all animal products and believes that nutrition has an impact. Based on her current status and treatment schedule, please advise if there is anything else she should do.

    She has HER2 type breast cancer. She had a 10 cm tumour and cancer was present in the lymph nodes. She has had 3 rounds of chemo, and has 3 more to go. The first 3 were FEC and the remaining 3 will be DH, and she will remain on H for one year. In January she will have a radical mastectomy of the affected breast (despite the fact that as of now her tumour has shrunk to 4 cm) and the lymph nodes will be removed as well. She will have daily radiation for 4-6 weeks starting one month after surgery.

    Many thanks!!

    • Joanne B, RD

      Thanks for reaching out. Your friend is lucky to have your support. While a plant based diet approach is certainly healthy, a couple of thoughts came to mind that you might want to check in with her about. First, how is her appetite and weight? A combination of diet change (especially if protein from animal sources have been eliminated and uptake of vegetarian sources isn’t quite there yet) and managing treatment related side effects can sometimes make it challenging for a person to get all the nutrients needed for health and healing. I would also be sure to encourage consumption of cancer fighting foods, herbs and spices and avoid supplements. For example, turmeric, a well known cancer fighting nutrient in culinary amounts is safe but steer clear of supplements. This is especially true during cancer treatment as we don’t want to inadvertently repair cancer cells! And of course always discuss with your oncologist. I hope this helps.