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June 3rd, 2011
03:51 PM ET

How much is too much phytoestrogen?

Every weekday, a CNNHealth expert doctor answers a viewer question. On Friday, it's Dr. Melina Jampolis, a physician nutrition specialist.

Asked by Keyana of Spokane, Washington:

I have two questions. What is considered to be a high/harmful amount of phytoestrogen in a woman's diet per day? And should a woman who has had cancer not take estrogen replacements or eat a diet high in phytoestrogens?

Expert answer:

Hi, Keyana. These are interesting questions. I'm going to assume that you are talking about breast cancer since the association of phytoestrogen consumption and breast cancer risk is the most concerning to many women.

Phytoestrogens are plant-based compounds that act like the hormone estrogen. There are two basic types of phytoestrogens: isoflavones and lignans.

Soy products are the most common source of isoflavones, and the controversy surrounding cancer and phytoestrogens are related to soy products. To provide you with the best possible response to your question, I turned to noted cancer nutrition expert Rachel Beller, who addresses this question on a regular basis at the Beller Nutritional Institute in Los Angeles.

Beller explained that while phytoestrogens are similar to human estrogens, their effect on human estrogen levels has not been well-researched because plant estrogens are 1,000 times weaker than the estrogen produced in our bodies.

Many studies suggest that soy isoflavones' estrogen-like effects are probably too weak to have any significant consequence on breast tissue in healthy women - that includes breast cancer survivors.

Regarding the association with breast cancer, Beller points to a 2011 study published in Cancer Epidemiology, Biomarkers & Prevention that found soy to be safe and favorable, even for breast cancer survivors, when eaten in its natural, unprocessed state - for example, tofu, tempeh, edamame, miso soup.

In fact, experts agree that fermented soy (miso, tempeh) is good for you. The fermentation process alters the chemical makeup of soy, which reduces the level of isoflavones by as much as 300%.

Therefore fermented soy foods have three times less of the chemical in question.

While this study does not conclusively establish the safety of soy, phytoestrogens aside, soy is not only an excellent source of heart healthy plant-based protein, which is encouraged in the latest dietary guidelines for Americans, it also contains dozens of nutrients that also appear to help fight cancer development.

These nutrients can protect cells from becoming damaged, encourage faulty cells to die instead of reproducing, regulate cell growth and even improve cell communication. These are all things that help strengthen your body against cancer and heart disease.

A study has also shown that consumption of soy early in life may help protect against breast cancer later in life, even if it may be more questionable for post-menopausal women.

What's also noteworthy is that Asians have been eating soy foods in large amounts for centuries, and their traditional soy-rich diets are associated with lower risks of breast and prostate cancer than Western diets.

Beller goes on to say that the "bad rap" that soy's been getting is due to the fact that when we hear something's "good for you," we process it to the max, extract the good stuff and concentrate it, which basically makes it lose its original identity.

Skip the processed soy foods and supplements, especially if you have a history of breast cancer.

The bottom line: If you have no history of breast cancer, there is no known high or harmful amount of phytoestrogens, and foods such as unprocessed soy are an important part of a healthy diet.

If you have a history of breast cancer, as with nutrition in general, you should not focus on a single food or nutrient. The key is moderation.

The phytoestrogens consumed by eating moderate amounts of relatively whole and unrefined forms of soy foods (two to three times a week) can be considered part of a healthy, complete diet.

Regarding estrogen replacement therapy, according to the National Cancer Institute, "Studies of hormone use to treat menopausal symptoms in breast cancer survivors have produced conflicting results," so I suggest speaking with your physician to determine the best approach for you.

Follow Dr. Jampolis on Twitter


soundoff (41 Responses)
  1. Bill

    How do you reduce something by 300%? Once you reach 100%, isn't it all gone?? Three times less of something means 1/3 the amount? Confusing....

    June 3, 2011 at 16:20 | Report abuse | Reply
    • phrasing

      The correct phrasing is "unprocessed soy products contain 300% more phytoestrogen content than processed products". Alternatively, "Processed soy products contain 33% of the phytoestrogen content of unprocessed products.". The only thing people really need to know is: "everything in moderation". People need to throw their supplements where the sun doesn't shine.

      June 3, 2011 at 17:10 | Report abuse |
    • kk

      phrasing, so we should change to supplement suppositories?

      June 3, 2011 at 18:13 | Report abuse |
    • Ken

      It really bugs me when so-called experts cannot do simple math.
      Yes, a 100% reduction takes any amount to zero.
      People get confused easily by percentage increases and decreases.
      They typically don't understand that a 100% increase followed by a 50% decrease puts you right back where you started.

      June 3, 2011 at 23:56 | Report abuse |
    • Harald

      Good observation Bill. While the actual decrease in isoflavones isn´t that much of an issue here, it bugs me that a medical doctor and sol called expert, did not even master the basic concept of percentage.
      It shows us once again, that, although this is a rather trivial example, that even expert opinions should always looked upon critically.

      June 4, 2011 at 15:57 | Report abuse |
  2. Sage

    Edamame (steamed soy beans) is truly unprocessed soy. Tofu and tempeh are fermented with a mold, like cheese, and therefore processed. What are you considering "processed" soy, if not tofu and tempeh? Does that mean soyburgers? Or only ordinary processed foods with soy added to increase the protein content? What about chocolate, which contains soy lecithin?

    June 3, 2011 at 16:46 | Report abuse | Reply
    • Mahna Mahna

      Natto is one of the few forms of soy that not only is safe, but has an immense list of benefits.

      June 5, 2011 at 00:31 | Report abuse |
    • D

      Tofu certainly seems processed to me. The fermentation process actually helps, so tempeh seems less "processed" in a way, but I agree that the answer is very poorly written and confusing here.

      June 5, 2011 at 15:17 | Report abuse |
    • Carrie

      Agreed, it's ridiculous to call tofu, tempeh, miso, etc. "unprocessed." If a product is extensively changed from it's original form by a food processing company, using cooking, soaking, grinding, extrusion, pressing, or chemical additives, then it's a processed food. It's true that in terms of soy, minor processing may be beneficial, as it reduces phytoestrogens and other toxic chemicals found in the raw beans and makes it easier to digest.

      June 5, 2011 at 21:07 | Report abuse |
    • eatwellbewell

      You are all so critical! Relax! You get the idea with the percentages. And processed soy would mean "faux" meats and other manufactured foods.

      March 17, 2012 at 09:50 | Report abuse |
  3. Burbank

    If soy causes cancer it is probably because it makes your body acidic. For people that have to watch thier acidic level such as gout sufferers, it's even worse than eating red meat or seafood.

    June 3, 2011 at 17:06 | Report abuse | Reply
    • Nancy

      Makes your body acidic? Your comment sounds like something from medieval times, when they thought mice arose from boiled wheat.

      June 5, 2011 at 11:36 | Report abuse |
  4. Lou

    Don't use soy products if you have gout. Either whole bean or supplements. Soy sauce seems to be ok.

    June 3, 2011 at 17:52 | Report abuse | Reply
  5. Rae

    Okay, you've covered the phytoestrogen part, now what about the lignans?

    June 3, 2011 at 17:54 | Report abuse | Reply
  6. Rae

    Okay, you've covered the isoflavone part, now what about the lignans?

    June 3, 2011 at 17:56 | Report abuse | Reply
  7. BC Patient

    I have estrogen positive breast cancer and was told by my doctor to stay away from soy products, processed or otherwise, because soy can behave as naturally occurring estrogen in the body – which, if one already has BC can potentially aggravate it. I was also told to eat flaxseed in moderation due to the lignans also behaving as estrogen does. Every breast cancer book I've read about diet recommends unprocessed soy. Yet my doctor says otherwise. Pretty conflicting. I guess, for a healthy woman, soy can be a healthy part of a diet. However for someone like me, maybe not.

    June 3, 2011 at 22:00 | Report abuse | Reply
    • D

      My sister's oncologist said the same thing as yours did. A little bit of soy sauce ok, but nothing else.

      June 5, 2011 at 15:18 | Report abuse |
  8. molson525

    I've been eating miso soup with tofu every day since March (about three months now) and I've seen a significant reduction in my perimenopause symtoms, particularly hot flashes and insomnia. I even have more energy. It works. The key is to eat it every day. Christian Northrup recommends about 1/2 cup of tofu, or 8 oz. glass of soy milk, or 2 handful of roasted soy beans.

    June 3, 2011 at 22:32 | Report abuse | Reply
  9. Dr. Cunuckian

    This entire article I find hokey at best,and borders on fraud. First off Mrs " Dr. Melina Jampolis, a physician nutrition specialist." is not a research scientist in the field of pharmaceuticals, nor does her field specialize in medicine. She also only points to one study that makes this entire article anadotal. Cnn is a corporate owned news agency that looks after its owncorporate interests. I suggest reading several studies instead of this CNN cherry picking one that is based on one doctors opinion that is not even somebody who is an expert in the field.

    June 4, 2011 at 05:13 | Report abuse | Reply
    • Johnny

      Good point.

      June 4, 2011 at 15:49 | Report abuse |
    • Nancy

      It is fraud. Phytoestrogens are abundantly secreted by the skin. Estrogen is a family of steroids, almost all of which are benign. Plants cannot produce estradiol or estrone, the chief ovarian hormones that are problematic in oncogenesis. Don't try to cut down on phytoestrogens - they are in all plants, some more than others - and they are harmless.

      June 5, 2011 at 11:32 | Report abuse |
    • D

      It is certainly unclear and poorly written.

      June 5, 2011 at 15:21 | Report abuse |
  10. karrie pittsburgh

    There is a danger in this article, with no warning about people whose thyroids are intolerant of soy. I have CFS, and if I eat the above mentioned soy things, it's a guaranteed 'crash'.

    Please do THOROUGH research with soy and thyroids before you jump on this wagon.

    June 4, 2011 at 07:37 | Report abuse | Reply
  11. Frangible

    I bet you a million billion dollars that's food allergies and has nothing whatsoever to do with your thyroid.

    If only there were giant machines that could measure the level of hormones in human blood...

    June 4, 2011 at 09:16 | Report abuse | Reply
  12. Betsy Griffin

    2 things: I am an ovarian cancer survivor – 12 yrs. remission- and for years have eaten lots of soy products to help me abstain from red meat protein needs and wants. In Jan. 2009 I was diagnosed with a meningioma brain tumor which has estrogen and progesterone receptors. I've always wondered if my daily consumption of soy products contributed to the slow development of this tumor and if I should get off of all soy. My radiation oncologist had no definitive answer for me and I can't find anything in reliable medical literature to help me with this delimma. The radiation surgery and side-effects of the medications was far worse than all my ovarian cancer surgeries and chemo treatment. Anyone out there ever researched this issue before? Thank-you.

    June 4, 2011 at 10:18 | Report abuse | Reply
    • BC Patient

      Hi Betsy, see my post. My doctor advises against the consumption of soy for this very reason. Of course I'm not suggesting that soy CAUSES cancer – not at all. It's just that there is no sufficient evidence that it aggravates existing cancer or contributes to a recurrence, etc. So to be on the safe side, I stay completely away. There are plenty of other healthy foods out there.

      June 5, 2011 at 09:48 | Report abuse |
  13. Countryboy

    Thyroids and soy bean burgers? http://WWW.CDBABY.COM/ALL/NUNONE bye now!

    June 4, 2011 at 11:13 | Report abuse | Reply
  14. Janice Stanger

    What you will never hear from doctors or the food industry is the high levels of estrogen in cow's milk (would be the same for goat, sheep or other mammal milk as well). These animals are kept constantly pregnant so they produce milk for dairy business people to sell. The estrogen from pregnancy gets into their milk and has virtually the same estrogenic activity as the human hormone. Don't worry about soy or flax seed. Both are healthy whole plant foods. If you want to avoid estrogen, go dairy free.

    June 4, 2011 at 17:25 | Report abuse | Reply
    • ANON

      Excellent point. Also, for links between food and cancer I would recommend reading "The China Study". Makes a compelling argument.

      June 7, 2011 at 15:19 | Report abuse |
  15. Mark Borsenik

    Dear Dr. Gupta, thank you for highlighting the conversations about paralysis & breakthroughs in Stem Cell therapy i hope to be able to take advantage of this someday!

    June 4, 2011 at 21:10 | Report abuse | Reply
  16. REBECCA

    96% of all consumed soy products in the US are GENETICALLY MODIFIED! I wish people do their research before believing the first they they hear about "soy is good for you"

    June 5, 2011 at 00:39 | Report abuse | Reply
    • Carrie

      Actually, pretty much all plants and animals that we eat have been "genetically modified" through extensive conventional breeding techniques. For decades, we've been dousing seeds with radiation to mutate them, then growing them to see if they exhibit any interesting/useful properties. Most of the industrial soy planted worldwide is "genetically engineered" or "biotech," meaning it contains genes from other organisms directly inserted into the genome. Agreed, we don't have much evidence yet as to whether Bt toxin expressed by the soy plant might be harmful to humans over the course of 20-30 years of consumption.

      June 5, 2011 at 20:58 | Report abuse |
  17. Elton R. Homan

    In the article, "How much phytoestrogen is too much?" the following appears: "... reduces the level of isoflavones by as much as 300%." Would you like to revise that?

    June 5, 2011 at 02:55 | Report abuse | Reply
    • moribundman

      There's three kinds of people: those who can do math, and those who can't.

      June 6, 2011 at 04:47 | Report abuse |
  18. Tobiwan

    Soy beans are not a health food. GM soy is even worse. soy baby formula amounts you need to factor in the size of the dose as with other drugs.

    For through and currant research on Soy, do a google search or go to http://www.mercola.com
    check out the archive there and get your eyes opened about soy.

    Tofu is not a fermented product, it is a cultured product like cheese

    June 5, 2011 at 08:07 | Report abuse | Reply
  19. Sandy

    Not mentioned is the fact that soy is one of the five major foods in the US grown by Genetically Modified Organisms....thank you, Montsanto........unless it is Organic and non-GMO, stay away from it!

    June 5, 2011 at 14:53 | Report abuse | Reply
  20. Frank

    Tell that to the boys growing breasts from Tee Tree oil.

    June 5, 2011 at 18:31 | Report abuse | Reply
  21. Chitra

    "...which reduces the level of isoflavones by as much as 300%.". Can you explain to me how is this calculation done? I mean I am not understanding the math here. Does it mean that the reduced isoflavone levels come in a negative number?

    June 6, 2011 at 01:54 | Report abuse | Reply
  22. Dann White

    How to take it? http://www.nutrovita.com/15780/solaray/phytoestrogen.htm

    August 6, 2011 at 01:43 | Report abuse | Reply
  23. how to take milk thistle

    I've been surfing online greater than 3 hours these days, but I never found any interesting article like yours. It's lovely value enough for me. Personally, if all site owners and bloggers made good content material as you probably did, the web will probably be much more helpful than ever before.

    April 10, 2012 at 20:40 | Report abuse | Reply
  24. Diane

    These articles are very convincing regarding the problematic levels of hormones in "modern" milk, meaning milk from animals milked far into pregnancy:

    http://harvardmagazine.com/2007/05/modern-milk.html

    http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3359127/

    I see one comment about natto above, but wish there was more written about what the natto bacteria do to the phytoestrogen content.

    July 6, 2014 at 14:02 | Report abuse | Reply

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