The confusion about soy and breast cancer.pdf

The Confusion About Soy And Breast Cancer
Valerie Franc B.Sc., N.D., C.Ht.
Doctor of Naturopathic Medicine
Certified Hypnotherapist
There has been much controversy and confusion about the safety of eating soy if you
have been diagnosed with breast cancer. Soy contains ‘phytoestrogens’, tiny components
of the plant that act as weak estrogens in the body. Many breast cancer (as well as other
types of cancer) tumors are estrogen positive – meaning that they grow bigger and faster
when they come in contact with estrogen. As well estrogen has been shown to play a role
in cancer formation. This has caused a concern for some oncologists as well as patients,
who feel that plant based ‘pseudo-estrogens’ will greatly increase the likelihood of
developing cancer. On the other hand, there are many doctors and researchers that
promote the use of soy products. They feel that eating soy actually helps prevent breast
and other types of estrogen related cancer. Who do you listen to?
Here’s What We Know:
Phytoestrogens can be split into two different types, isoflavones and lignans. Soy
products contain isoflavones, specifically ones called genistein and daidzen (genistein is
stronger than daidzen). Some herbs, legumes and sprouts also contain isoflavones.
Flaxseeds are a common source of lignans, but they can also be found in pumpkin seeds,
berries, some vegetables and many grains.
We are so used to hearing the term estrogen that we commonly think it is just one
molecule, but it is not. There are 3 types of estrogen found in the body, each with
different strengths. Estriol is the weakest acting form of estrogen, and has been associated
with protection against cancer. Estrone and estradiol are much stronger acting forms of
estrogen. These two forms are associated with cancer formation. It is interesting to note
that almost all forms of hormone replacement therapy and birth control pills use a form of
estrogen known as17 beta-estradiol. This is the strongest estrogen and is known to
promote cancer.
Pro Soy
Phytoestrogens act as weak estrogens (similar to estriol). They bind to breast (and other
estrogen sensitive tissues such as the uterus) cell receptors, and prevent other stronger
estrogens (such as estrone and estradiol) from binding. As a result strong estrogens are
unable to act on tissues and are excreted from the body, preventing them from initiating
cancer growth (1). Although phytoestrogens are strong enough to bind to the receptors, it
is important to note that they are too weak to affect the DNA of the cell. Therefore they
are unable to promote or initiate breast cancer. Another benefit of phytoestrogens is that
they increase the production of steroid hormone binding globulin (SHBG). SHBG is
responsible for binding to estrogen and carrying it through the blood. As the number of
these transporter molecules increases, the amount of free estrogen available to bind to
tissues decreases. Therefore there is less estrogen available to promote cancer growth and
formation. In short phytoestrogens can have an anti-estrogenic affect on breast and
uterine tissues. At the same time, they still have a weak estrogenic effect on other tissues
such as bone (this is important in osteoporosis treatment and prevention).
Research has shown that soy isoflavones (particularly genistein) can help prevent as well
as reverse breast cancer (2,3). They have been found to be involved in processes that help
the cell to grow and divide normally. They also help protect cells from being damaged by
free radicals (well known to accelerate aging as well as cause cancer). In this way they
help prevent cancer (4). There is evidence that they are involved in a process (called
apoptosis) that tells damaged cells to die. They have been proven to prevent cancer cells
from making new blood vessels and can turn off breast cancer genes (by shutting down
protein kinases). As a result phytoestrogens can help treat cancer as well. Studies of
differing populations show that women in North America are 2/3 more likely to develop
breast cancer than Asian women, who eat an average of 50 grams of soy per day (5).
Against Soy
The main argument against soy products is that all estrogens are bad estrogens whenever
breast cancer is concerned. Better to be safe than sorry is a motto for some. Since the
phytoestrogens in soy look similar to and admittedly act as weak estrogens, they must act
like strong estrogens too. This thinking however is incorrect, as it assumes that all
estrogens weak or strong act the same.
Let’s review some facts about estrogen. As previously stated, the estrogens in our bodies
are not one but three different molecules, and each of the molecules have a particular
strength. Estradiol is the strongest of the three, and is used in estrogen containing
hormone replacement and birth control pill formulas. Estradio l has been proven in
research to bind to receptors in estrogen sensitive tissues (such as breast and uterus) and
stimulate growth. It can actually affect DNA in the cells, and therefore increases the
likelihood of damage occurring. Estrone is weaker in strength than estradiol, but is still
considered strong acting. Estrone and estradiol can be converted into each other in the
body as well. Therefore estrone has the same cancer initiating and promoting effects as
estradiol. Estriol, the third type of estroge n molecule has a weak acting effect on the
body. This estrogen molecule looks very similar to phytoestrogens, and acts very
weakly on breast and uterine tissues. Research has actually shown this type of estrogen
can help prevent cancer. The reasons for this are similar to those supporting the use of
soy in breast cancer treatment and prevention. Estriol binds to receptors and therefore
prevents stronger acting estrogens from doing so. Therefore these stronger estrogens are
unable to cause damage.
There is also new evidence supporting the thought that the three estrogens affect tissues
differently. It has been found that weak acting estrogens are more active on tissues such
as bone, and less active on tissues such as the breast and uterus. It is this understanding of
the different forms and actions of estrogens that have produced a new type of drug called
a SERM (Selective Estrogen Receptor Molecule), which is being used in the treatment of
osteoporosis (Note: this drug is currently being researched as an alternative to Tamoxifen
in breast cancer prevention). Another important thing to remember is that estrogens can
have a positive effect on our bodies as well. They are known to promote bone growth and
help prevent osteoporosis. Therefore it is too much of the strong estrogens (i.e. estradiol
and estrone) that lead to cancer growth and development. Estriol is helpful in preventing
breast cancer, and phytoestrogens (which have a similar action in the body) are as well.
While phytoestrogens are not in and of themselves associated with the promotion and
initiation of cancer, there is a reason to be cautious of some soy products. In the last
decade in particular soy products have been genetically altered to increase production and
crop yields for farmers. The concern is that as a result soy products are being saturated
with pesticides, which are contaminating foods products and increasing the incidence of
breast and uterine cancer in those who consume high amounts. Therefore experts in the
field currently recomme nd eating only organic soy products and limiting soy in particular
to 1 serving per day. As well pesticide soaked soy byproducts (i.e. left over waste that is
not used when making soy milk and tofu) are being used as fillers in many processed and
packaged foods such as hotdogs. By reading all your labels carefully and eating only non-
genetically modified and organic soy products, you can avoid the pesticides and lower
your risk of breast cancer.
How Much Should I Be Getting?
In general 80 to 160 mg of isoflavone, or 35 to 60 grams of organic soy per day is
recommended to help prevent breast cancer. In her book “A Call To Women: The
Healthy Breast Program and Workbook” (this book is a must have for every woman!),
Sat Dharam Kaur N.D. recommends what she refe rs to as the “Fabulous Five”
1. Freshly Ground Flaxseed: 2 – 4 Tablespoons daily 2. Organic Tofu and Soy Products: ½ cup tofu or 1 ½ cups soy milk daily 3. Raw Pumpkin Seeds: 1 – 2 Tablespoons daily 4. Clover Sprouts: 3 or more cups weekly 5. Mung Bean Sprouts: 3 or more cups weekly
Eating these five foods as recommended will make sure you get all the isoflavones and
lignans you need. If these foods don’t appeal to you, or if you are having difficulty
incorporating them into your diet, you can get isoflavones in a capsule form from your
local health food store (be sure to get a good, reputable brand – see your local Doctor of
Naturopathic Medicine for suggestions).
Best wishes to all.
1. Walker, Morton. Soybean isoflavones lower risk of degenerative disease. Townsend
Letter For Doctors And Patients, Aug/Sept, 1994. 2. Ingra, D.K. Saunders, M. Kolybaba, D. Lopez. Case controlled study of phytoestrogens and breast caner. Lancet, 1997:350 Oct 4:990-93 3. Ingra, D.K. Saunders, M. Kolybaba, D. Lopez. Phyto-estrogen and breast cancer. Int. Clin. Nutr. Rev., 1998; 18(1):35-36 4. Constantinou et al. Untitled. Cancer Res, 1990; 50:2618-24 5. Kennedy, A. The evidence for soybean products as cancer preventative agents. J.


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