Soy and Breast Cancer

soybean

At present, confusion and controversy surround the inclusion of soy in the diet of those women with estrogen-positive, postmenopausal breast cancer.

Research on soy and breast cancer presents a conflicting picture. Many studies have shown a protective effect, many have not. One study found that the major phytoestrogens in soy, genistein and daidzein, stimulated breast tumor growth in laboratory and in animals at low concentrations but had the opposite effect at high concentrations. In yet another study, soy and curcumin together produced a 100% effect in stopping tumor growth.

It was reported that premenopausal Singapore Chinese women who are high consumers of soy have a reduced risk of breast cancer in Since then, there has been tremendous interest in the possible role of soy in the prevention of breast cancer. However, there is also the concern that soy may have stimulatory effects on the breast.

The fact that Japanese consume soy and have very low breast cancer rates is often used to ‘prove’ that soy can help prevent breast cancer. But traditional Japanese diets differ from typical Western diets in many ways so it could be something else that is causing that. For example, they eat lots of fish and seaweed. Also, Japanese consume soy in fermented form, and usually only as side dishes, in small amounts, and not as main staple. So more research is needed on soy.

It is currently unclear whether phytoestrogens from soy foods affect breast cancer risk. Studies looking directly at breast cancer risk and soy in the diet are not in agreement. Almost half of the studies have reported no effect of soy on breast cancer risk. In addition, animal and cellular studies of soy phytoestrogens have generated both enthusiasm and concern. Animal studies have shown that soy phytoestrogens can decrease breast cancer formation in rats. However, animal and human studies suggest that soy phytoestrogens can behave like estrogen and potentially increase breast cancer risk. Some scientists have suggested that women should be cautious about eating large amounts of the soy products or soy supplements, because of the possible harmful effects of soy phytoestrogens.

The overall conclusion and value of this comprehensive analysis is that the available evidence does not support a recommendation for increased soy consumption as a breast cancer-preventing agent against the background of a Western diet. Instead, additional general components of the Asian diet, such as fish and plant-based food, may be involved in lowering breast cancer risk.

And now the facts about soy and breast cancer

Soybeans contain many potentially anticarcinogenic compounds, including saponins, phytates, protease inhibitors, and isoflavones (weak estrogen compounds).

These foods have been shown to block the estrogen receptors and therefore, eliminate excess estrogen prior to multiplying more cells. These are natural estrogens and weaker than some natural estrogens and most synthetic estrogens.

Soy isoflavones could prove to be important in preventing against breast cancer too.

A large number of studies have demonstrated that certain phytochemicals in soy beans help to reduce the risk of cancer, and that the bioavailability of these substances is greatly increased by fermentation. Fermented soy products such as miso, tempeh and natto are a natural part of the diet of the Chinese and Japanese, who have a low risk of breast, colon and prostate cancer (though this may also be related to other dietary and lifestyle factors).

When 144 women with early breast cancer were matched with healthy controls (same age and area of residence), blood and urine analysis revealed a substantial reduction in breast cancer risk among those who had a high intake of soy isoflavones.

In another study, pre-menopausal women who ate 60grams of soy protein every day for a month showed hormonal and menstrual cycle changes associated with a reduced risk of breast cancer.

The phytochemicals in soy responsible for its anti-cancer properties include the isoflavones, genistein and daidzein. Genistein prevents cancer cells from producing proteins that help cancer cells survive the attacks of the body’s immune system. Genistein and daidzein also have antioxidant effects. Additionally, they have been shown to inhibit the proliferation of cells in various cancer cell cultures, including breast cancer, prostate cancer, sarcoma, neuroblastoma, and retinoblastoma. Genistein has also been reported to inhibit angiogenesis (the growth of new blood vessels required by developing tumors). Other soy substances have been shown to reduce cholesterol levels by binding to the cholesterol in the intestines, inhibiting its absorption.

On the other hand…..

Dietary genistein and highly processed soy agents have been found to stimulate growth in the MCF-7 breast cancer cells, and to promote breast cancer in ovaraectomised athymic mice models. In a short term soy-feeding trial, women randomized to the soy arm exhibited significantly higher indices of increased DNA synthesis relative to women in the control arm, although this apparent association failed to persist following the inclusion of 33 additional subjects

Soy can cause breast cancer as well

Highly purified soy foods and supplements sold in the United States may stimulate the growth of pre-existing estrogen dependent breast tumors, according to a study from the University of Illinois. "Soy has been correlated with low rates of breast cancer in Asian populations, but soy foods in Asia are made from minimally processed soybeans or defatted, toasted soy flour, which is quite different from soy products consumed in the U.S., said William G. Helferich, a professor of food science, in a study published in the journal Carcinogenesis.

Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women.

Genistein, one of soy’s components, has been shown to make tumors grow when taken alone, but is fine when it’s consumed with the entire soy product

Two senior US government scientists, Drs. Daniel Doerge and Daniel Sheehan, have revealed that chemicals in soy could increase the risk of breast cancer in women, brain damage in both men and women, and abnormalities in infants.

The scientists decided to break ranks with colleagues in the FDA and oppose its decision last year to approve a health claim that soy reduced the risk of heart disease.

They wrote an internal protest letter warning of 28 studies revealing toxic effects of soy, mostly focusing on chemicals in soy known as isoflavones, which have effects similar to the female hormone estrogen.

They claim that research has shown a clear link between soy and the potential for adverse effects in humans.

Practical conclusions:

1. Avoid processed soy products

One thing is clear to most alternative health practitioners that certain derivatives of soy, such as soybean oil, soy lecithin, hydrolyzed vegetable protein, hydrolyzed soy protein, and soy protein isolates should be avoided. Many milks and tofu-based ice creams are from SPI. SPI is a cheap way for companies to add protein to energy bars to make them seem healthful. The soy protein isolate is actually the left over by-product of creating soy oil so instead of throwing it away, it gets added to processed foods to add protein. In order to extract the protein and reduce the enzyme inhibitors in soy, they must be treated with a high temperature chemical process. Toxins and carcinogens are created during this process including nitrates, MSG, and lysinoalanine. Read your ingredients well and avoid foods that contain:

That includes soy protein isolate and concentrates, genetically engineered soy foods (typically made from Monsanto’s Roundup soybeans), soy supplements, and soy junk foods like soy cheese, soy ice cream, soy oil, and soy burgers. They don’t have the thousands of years of traditional use that whole soy foods do, are processed, and contain unhealthy fats and other compounds. The simple fact is that there are little or no isoflavones in many commercial products. In addition, sugars and fillers represent a major component of many commercial isoflavone products.

Read your ingredients well and avoid foods that contain:

* Hydrolyzed Soy Protein
* Hydrolyzed Vegetable Protein
* Soy Flour
* Soy Oil (also look for Vegetable Oil – most is actually soy oil)
* Soy Lecithin (GMO especially)
* Soy Protein Isolates (SPI)
* Textured Vegetable Protein (TVP)

2. Avoid even so-called “natural” unfermented soy products

Unfermented soy contains high levels of a number of compounds that can:

Block the absorption of calcium, magnesium, iron and zinc;
Stunt growth and alter hormone levels, disrupting menstruation, lowering testosterone, increasing the risk of breast cancer, and causing thyroid and prostate complications.

Unfermented soy includes things like whole soybeans, soy milk, soy chips, soy protein isolates, soy milk, soy burgers, soy hot dogs, and tofu. soy flour and all the other myriad of products made from processed soybeans and advertised as health foods.

Soy milk in particular should be avoided. 1. Many soy crops are heavily treated with pesticides, 2. Most commercially available brands of soymilk contain the thickening agent carrageenan, a seaweed derivative, which may be harmful to the intestinal tract.

Consumers need to recognize there are little or no isoflavones in many commercial products. In addition, sugars and fillers represent a major component of many commercial isoflavone products.