Enjoy Soy

Thomas Lodi, MD, MD(H), CNS

Soybeans are a species of legume, like chickpeas, lentils, peanuts, alphalfa and carob, all of which are classified in the family Fabaceae.  Soy beans are like many legumes capable with the help of certain bacteria that live in their roots of “fixing” nitrogen directly from the atmosphere into organic compounds.  It is this process of taking nitrogen from the air and combining it with an acid (“fixing”) that results in amino acids which form the building blocks of protein. For this reason, the soybean contain as complete a protein as animal flesh but without the violence or blood.

It is unclear exactly when soy actually entered the human diet but probably during the Zhou dynasty (1046-256 BCE), the same era that brought about hydraulic engineering.  Raw soybeans are toxic to humans due to the trypsin inhibitors and phylates they contain; hence, they must be modified prior to eating. Early during the Zhou dynasty, it is believed fermentation techniques were applied to soybeans producing the very same foods eaten today in Japan and China like natto, miso, tempeh as well as soy and tamari sauces.  Sometime after the application of techniques for fermenting soybeans, bean curd (tofu) was introduced.  

Although cooking can greatly reduce the concentration of trypsin inhibitors, some remain, as do the phylates, which are completely eliminated with fermentation. Since the trypsin inhibitors block protein digestion and the phylates chelate essential minerals, they are considered to be “anti-nutirents”. Indigenous Chinese, Japanese and Koreans have known this for over a millennia but, as usual, science rejects wisdom in favor of naïve folly and must go about proving that apples actually do fall to the ground.

The use of soy with regards to cancer, especially hormonally related cancers such as breast, uterine, ovarian and prostate remains controversial in the public arena however, a careful review of the scientific literature regarding soy, makes it abundantly clear that it is not only safe but is both preventative and therapeutic.

It is well known that breast, uterine and ovarian cancers for women born and raised in Asia have been historically lower than in Western countries. And it is further recognized that once Asian women immigrate to the United States, there is a significant acceleration in the incidence of these cancers. This is particularly true of Japanese women, where the dietary factors have been well described in many studies comparing the incidences of these cancers for women born, raised and who remain in Japan vs. those who emigrate to Hawaii vs. those who emigrate to the US Mainland, as adults.  

In all these studies, the incidences increase sequentially from Japan to Hawaii to the Mainland, US and diet is clearly identified as the major contributing factor. The dietary differences identified include both an increase in Western food and a decrease in traditional Japanese food (e.g., soy) for emigrants to Hawaii and an even greater change for those having moved to the US Mainland.

Consuming soyfoods has been found to be inversely correlated with the incidence of breast cancer in both pre and post menopausal women, albeit there is a greater protective effect for post-menopausal women. However, in one large prospective cohort study in Japan, it was found that frequent miso soup and isoflavone consumption reduced the risk of breast cancer, whereas the same was not found in association with the consumption of non-fermented soyfoods.

It is well known that increased density of breast tissue is linked to a higher risk of breast cancer; hence the findings in a joint study reported in July 2002 (Cancer Research UK, the National Cancer Institute of the USA, and the National University of Singapore) were quite significant. They clearly indicated that women with a diet high in soy were found to have less dense breast tissue than women with low soy diets.

In other studies, eating soy phytoestrogens regularly over several weeks actually reduced innate estrogen levels. That is, eating soy resulted in lower estrogen levels.

Quite a few very large studies that followed women over several years all indicate that soy is protective against endometrial (uterine) cancer. When compared with women who do not eat soy, women who regularly eat soy have a significantly lower risk of endometrial cancer.

Although most studies suggest that soy protects against ovarian cancer, some indicate no reduced risk.  Howeverin none of these studies is their any suggestion that soy increases the risk of ovarian cancer. Hence, the scientific literature is reassuring in that it affirms that soy does not increase ovarian cancer risk.

Several studies in China, Japan and the US have clearly shown that the consumption of soy products is protective against prostate cancer, reducing the risk significantly. In one large meta-analysis published in 2005 the authors concluded, “In summary, the results of our meta-analysis of available epidemiologic studies demonstrated that consumption of soy food was related to a lower risk of prostate cancer in men.”

Compounds Found in Soy

Polyphenols are secondary metabolites produced by plants in order to defend against UV radiation  (sunlight) and plant pathogens. These compounds are able to quench free radicals, hence they are anti-oxidants.

The same mechanism of quenching oxidative by-products (free radicals) is necessary for all mammals, especially humans who were not satisfied with the normal, natural array of oxidants so they went to extraordinary lengths to produce an overwhelming number and kinds of artificially produced oxidants (free radicals).

Favonoids are the most studied subgroup of polyphenols with more than 4000 varieties having been identified. Isoflavones quercetin, lignans, catechins, flavanones, curcumin, ellagic acid, red wine polyphenols, and resveratrol found in a variety of plants including green tea, grape seeds, citrus peels, blueberries, soy and ginkgo leaves have been extensively researched.  All of them show protective and/or therapeutic effects with regards to cancer. Of the 6 subclasses, isoflavones are of special interest for hormonally related cancers.

Soy contains three isoflavones; genistein, daidzein and glycitein.  The isoflavones found in soy (phytoestrogens) are biochemical structures very similar to the natural estrogens produced by humans and can produce similar effects as estrogen.

Fermenting soybeans converts them into a form, which is more bioactive and readily assimilated by the body. However, even with unfermented soy products, if there is a healthy digestive system with abundant, beneficial bacteria, even the unfermented soybeans can be converted (somewhat) into more bioactive forms.  Unfortunately, most people with cancer have disturbed digestive systems and moderate to severe microbial imbalance in their guts with yeast overgrowth and pathogenic bacteria.

These isolflavones can significantly inhibit the growth of tumors, tumor invasiveness and stop metastases, as well as enhance the effectiveness of radiation therapy (although this is usually an unnecessary and very dangerous therapy).

Genistein significantly decreases both cancer cell invasion and progression via direct effects on different processes in the nucleus (DNA). It actually directly affects gene expression and transcription, hence completely interfering with the malignant process.

By decreasing inflammation, as measured by NFkB activity, isoflavones are able to reduce resistance to chemotherapy drugs AND diminish the overall aggressiveness of cancer. In fact, high phytoestrogen isoflavone intake has been shown to reduce recurrence rate and mortality in breast cancer.

Estrogen Receptors and Soy

There are two forms of estrogen receptors, alpha and beta to which estrogens can bind. The beta-receptors have been found to be inhibitory, hence when they are activated, it slows or stops breast cancer growth and invasion (inversely correlated with risk).

Unlike natural estrogens, phytoestrogens (isoflavones) preferentially bind to beta-receptors. Isoflavones are referred to as SERMS or selective estrogen receptor modulators. Therefore, they sometimes act like estrogen and sometimes they have the opposite effects and sometimes no effects at all.  Additionally, phytoestrogens, like genestein can actually enhance the effects of certain drugs used by onolcologists, like Herceptin for HER2(+) breast cancers.

These phytoestrogens have also been found to be extremely effective with prostate, ovarian, cervical, and colon cancer with regards to prevention as well as treatment. Finally, they actually sensitize these malignant cells so that both chemotherapy and radiotherapy are more effective suggesting that lower doses may provide the same or better results.

Controversy…Fear of Soy

Much of the controversy regarding the use of soy (or isoflavones) with ER (+) breast cancer has been based on studies with mice who had their ovaries and/or thymus glands removed, rather than women with breast.  This extrapolation is really too far reaching and is not consistent with the epidemiological evidence of low breast cancer rates in Asian women who have a high dietary intake of soy phytoestrogens.

The glaring fact that phytoestrogens are safe and have been consumed by humans for millennia is evidence that our ‘scientific model’ regarding how to uncover (learn) the “truth” is not only inexact but is actually counterproductive and dangerous.

After all, consider how much research and speculation have filled countless volumes of paper and computer storage software discussing whether or not to use a plant that has been consumed in large volumes by human beings for more than 2000 years, while readily approving, manufacturing and administering incredibly toxic substances continually with relative ease. It is time that we come back down to Earth, open our hearts and minds so that common sense can once again prevail rather than manufactured opinion to further commercial interests.

References available upon request

Japanese continue to eat several servings of both fermented & unfermented soy foods daily and they continue to outlive people in Western countries in spite of the fact that they are now also consuming more Western food.  


Fermented Soy Products

Natto (Nattokinase)



Soy sauce (tamari)

Fermented tofu

Fermented soy milk

Pickled tofu


Non-Fermented Soy Products

Soy milk


Fresh green soybeans

Whole dried soybeans

Soy nuts & chips

Soy flour

Soy sprouts

Soy cheese / veggie cheese

Soy infant formula

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