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Effect of soy consumption on breast cancer

There's uncertainty regarding the effects of soy isoflavones in post-menopausal women. Studies have shown that soy isoflavones may provide post-menopausal women with the same benefits of hormone replacement therapy (HRT): reduction of hot flashes, vaginal dryness and protection against heart disease and bone loss (osteoporosis). Researchers have only recently started to investigate the possible effects of soy to breast cancer. More and more women who are adding soy to their diets to help prevent breast cancer but researchers are unsure of the exact effects.

How can soy protect against cancer?

Some animal studies and small human clinical trials have shown that soy foods may offer some protection against breast cancer. Researchers believe that isoflavones may help protect against breast cancer because isoflavones compete with natural estrogen in the body to bind to special estrogen receptors on cells.
It is known that estrogen stimulates breast cell growth. Because isoflavones may block estrogen from reaching estrogen receptors, pre-menopausal women who include soy in their diet may decrease their risk of breast cancer.

Does soy increase risk of breast cancer?

Whether soy can help protect against breast cancer in post-menopausal women is unclear at this time. It remains controversial whether women diagnosed with breast cancer should be advised to eat more or less soy foods. Some researchers believe that soy consumption may actually increase the risk for breast cancer in post-menopausal women because the chemical structure of isoflavones is very similar to estrogen. Although experts say the effects are still unknown , no studies have clearly shown that that consumption of soy by humans increase breast cancer risk. Asian women, who consume more soy than Western woman, have a breast cancer rate one-fifth that of Western women. Also unknown are the effects of phytoestrogens on women who already have breast cancer or those at risk because of genetic factors. A study at the Wake Forest University School of Medicine, entitled "Breast and Uterine Effects of Soy Isoflavones and Conjugated Equine Estrogens in Postmenopausal Female Monkeys", published in the The Journal of Clinical Endocrinology and Metabolism, suggested that high dietary levels of soy isoflavones do not stimulate breast or uterine proliferation in postmenopausal monkeys and may contribute to an estrogen profile associated with reduced breast cancer risk [1]. A more recent study investigated the association of dietary intake of isoflavone with all-cause mortality in 6235 women with breast cancer [2]. During a follow-up of about 9 years 1224 deaths were reported. The mortality for women who had the highest versus lowest quartile of dietary isoflavone intake was 21% lower.


[1] Breast and uterine effects of soy isoflavones and conjugated equine estrogens in postmenopausal female monkeys. J Clin Endocrinol Metab. 2004 Jul;89(7):3462-8.
[2] Dietary isoflavone intake and all-cause mortality in breast cancer survivors: The Breast Cancer Family Registry. Cancer. 2017 Mar 6. doi: 10.1002/cncr.30615.


Soy and breast cancer

I was initially told that soya milk enhances breast growth but now am seeing something like it causes breast cancer.....can someone help me out so i dont do the wrong thing or is there any other way of enhancing breast growth?
Tosin - 22/10/2013

Soy and breast cancer

You can find many references claiming that soy consumption increases breast growth. Some companies even sell supplements with isoflavones to promote breast growth. Soy contains isoflavones, a plant-derived estrogen. Human estrogen is necessary for breast development and increasing soy consumption may enhance breast growth. But there is little scientific evidence to support these claims.

And what about the link between soy milk consumption and increased the risk of breast cancer? In recent years the relationship between soyfoods and breast cancer has become controversial because of concerns, mainly based experiments with rodents and in test tubes, that soy isoflavones may stimulate the growth of existing estrogen-sensitive breast tumors. But according to a study by Mensina and Wood (1) "there are no data to support the idea that soyfoods or isoflavones supplements improve the prognosis of breast cancer patients". They found that the intake of soyfoods and supplements, when taken at dietary levels, had no influence on breast cancer recurrence and mortality.

(1) Soy isoflavones, estrogen therapy, and breast cancer risk: analysis and commentary. Nutr J. 2008 Jun 3;7:17.
Rob - 23/10/2013

cancer patient and soya base food

Can cancer patient take soya based food like taufofa?
sheiza sharin - 01/05/2014

Soya products and cancer

Scientific studies indicate that soya products are safe for cancer patients and that they actually reduce the risk of many cancers. However, women with estrogen-positive breast cancers are often advised by doctors to limit their intake of soy products. This is because soya isoflavones are structurally similar to human estrogen, which is known to increase breast cancer risk. But this similarity does not necessarily mean that soya isoflavones increase breast cancer risk. Recent studies indicate that soya isoflavones may actually lower recurrence among postmenopausal women.

Rob - 01/05/2014

cancer patient and soya base food

I just read a recent study "Soy products in the management of breast cancer" that concluded that soy foods consumed at levels comparable to those in Asian populations have no detrimental effects on risk of breast cancer recurrence and in some cases significantly reduce the risk. In addition, soy products do not appear to interfere with tamoxifen or anastrozole therapy.

Joseph - 02/05/2014

soy milk does not cause cancer

soy milk does not cause fact its proven that it can reduce the risk of certain cancers such as breast, uterine and colon.
guest - 25/11/2017

Soy isoflavones and breast cancer

ok you guys I see conflict and I'm looking for facts rather than opinion if it's alright. I'm diognosed with stage 4 cancer that is very estrogen pos. I know soy has natural phyto-estrogens. I'm wondering if the processed wax would remove any of it. Soy wax is working well as a base for a homemade medicinal slave I apply all over body. I am a little nervous about using it now. Any info would be greatly appreciated thanks.
happy to be here - 08/07/2018

Soy isoflavones and breast cancer

Some doctors warn against the consumption of soy foods by woman with estrogen positive breast cancer, but this warning is also not based on facts, only on opinions! A recent study (1) mentions that "a moderate consumption of diet containing this isoflavone does not increase the risk of breast cancer recurrence in Western women, and Asian breast cancer survivors exhibit better prognosis if they continue consuming a soy diet". Another recent study (2) concluded that "among women with breast cancer, soy food consumption was significantly associated with decreased risk of death and recurrence".

I don't know the composition of your soy wax, but if it is made from soy bean oil it will contain probably no isoflavones. Soybean oil is on the USDA list of Foods Containing Zero Values for Isoflavones.

(1) Is soy consumption good or bad for the breast? J Nutr. 2010 Dec;140(12):2326S-2334S.
(2) Soy food intake and breast cancer survival. JAMA. 2009 Dec 9;302(22):2437-43.
Rob - 08/07/2018

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