Soy-Linked Breast Cancer – What Are The Facts?

Breast Cancer and soy foods and products have recently been linked (providing some benefits against breast cancer and other conditions in some women and quite the opposite effect in others). If you are considering adding soy to your diet to help prevent breast cancer, you should first talk to your doctor, especially if you have a personal or family history of breast cancer or other medical problems.

Does Soy Offer Breast Cancer Protection?

Countless studies have shown that Asian women have a breast cancer rate just one-fifth that of Western women, and the link has been made to their high consumption of soy. Soy is a staple food in the Asian diet, commonly consumed as tofu. Even though these studies have shown a lower rate of cancer, the reasons for this are not fully understood, and research continues to point in both directions.

Soy, Phytoestrogen and Isoflavones

Generally, soy foods are rich in phytoestrogens, which are natural chemicals that perform like a weak form of estrogen. Isoflavones are one particular kind of phytoestrogen. Some researchers believe that these isoflavones alleviate menopausal symptoms and can help to prevent breast cancer in some women. Phytoestrogens are commonly found in alfalfa sprouts, flaxseeds, soybeans, black cohash and other plants.

The effects of phytoestrogens are not completely understood, but many researchers believe that they compete with estrogen to reach estrogen receptor sites in different parts of the body such as breast tissue. Estrogen stimulates cell reproduction, so it is believed that the more exposure a woman has to it, the greater her breast cancer risk. In premenopausal women, it appears that phytoestrogens reduce estrogen levels because they attach to estrogen receptor sites, tricking the body into producing less estrogen.

Soy and Postmenopausal Women

However, in postmenopausal women the effects are less clearly understood. A postmenopausal woman’s estrogen levels are naturally lowered and there has been no evidence that consuming soy reduces breast cancer risk in this group of women. Many doctors actually believe now that phytoestrogens boost the estrogen levels of postmenopausal women and can increase the risk of breast cancer.

It is also unknown what the effects of phytoestrogens are on women that have had breast cancer or are at a risk of developing it. It is thought though, that high isoflavonoid intake will stimulate cell growth and should be avoided to prevent future cancer reoccurances.

Finding a Connection Between Breast Cancer and Soy

At the present time, there are not clinical trials to support eating a specified amount of soy products over a period of time can reduce breast cancer risk. There are some animal and in vitro studies of cancer tissues that have established a connection between reduced breast cancer risk and isoflavonoids, but no clear-cut relationship has been established.

Though the link between breast cancer and a diet rich in soy has not been clearly established, nutritionists do agree that there are many health benefits to eating a diet filled with soy products such as tofu. Whether or not (and how) this diet contributes to cancer prevention is not fully known. If you have a history of breast cancer, are at high risk or are postmenopausal, you should consult with your doctor before adding soy to your diet.


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