Concerns raised over soy supplementation: Study

By Nicola Cottam

- Last updated on GMT

"These data raise concern that soy may exert a stimulating effect on breast cancer in a subset of women."
"These data raise concern that soy may exert a stimulating effect on breast cancer in a subset of women."

Related tags Breast cancer Cancer

Soy supplementation for women suffering from breast cancer may compound rather than improve their condition – contrary to popular opinion, say scientists.

Epidemiological studies suggest soy supplementation can benefit breast cancer sufferers but there is conflicting evidence concerning its efficacy, the researchers wrote in the Journal of the National Cancer Institute.

Soy can exhibit either pro- or anti-estrogenic effects and may affect other cellular events, so it could be both protective and harmful, explained lead scientist Dr Moshe Shike.

“Soybeans contain the isoflavones genistein and daidzein. Genistein stimulates growth of estrogen-sensitive breast cancer (BC) cells and can block the inhibitory effects of tamoxifen. However, isoflavones have also been reported to decrease BC cell growth,”​ he said.

Two-fold increase in genes

In the randomised placebo-controlled study, Dr Shike and his team in New York analysed the effects of soy supplementation on gene development and markers of breast cancer risk among women diagnosed with invasive breast cancer (adenocarcinoma).

When tumour tissue from the diagnostic biopsy and post-treatment surgery was examined the researchers observed changes in several genes that promote cell cycle progression and proliferation among women in the soy group.

A two-fold increase in gene expression was observed in some cases, including the FGFR2 gene known to induce cancer growth. This was possibly linked to raised levels of genistein.

“A high-genistein signature consisting of 126 differentially expressed genes was identified from microarray analysis of tumours. This signature was characterised by over-expression of cell cycle transcripts, including those that promote cell proliferation.”

In one sample gene expression increased from already elevated pre-treatment levels, which suggested the initial molecular alteration was reinforced by soy.

"These data raise concern that soy may exert a stimulating effect on breast cancer in a subset of women."

Study details

The four-year study (from 2003 to 2007) involved 140 patients scheduled for resection (surgery) who were randomly chosen for either soy supplementation (soy protein) or placebo (milk protein).

Patients were instructed to take two 25.8g packets of supplementation per day mixed with water or juice from the day of consent to the day of surgery.

To see the soy sector response to this research click here​.

Source: Journal of the National Cancer Institute

‘The effects of soy supplementation on gene expression in breast cancer: a randomized placebo-controlled study’


Authors: Moshe Shike, Ashley S.Doane, Lianne Russo, Rafael Cabal, Jorge, Reis-Filo, William Gerald, Hiram Cody, Raya Khanin, Jacqueline Bromberg, Larry Norton

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1 comment

There is no scientific evidence that soyfood consumption poses risk for breast cancer patients

Posted by ENSA (European Natural Soyfood Manufacturers Association),

Soy foods are part of a healthy and balanced diet and can be safely consumed by all groups of consumers, including breast cancer patients and survivors.

Current body of scientific knowledge does not have any evidence that soyfood consumption presents a risk for cancer patients. In fact, in November 2012 the American Institute for Cancer Research (AICR) extensively evaluated the findings from laboratory, animal and human studies and concluded that regular soyfood consumption has no harmful effect at all and even has the potential to reduce a risk of breast cancer.

It is misleading to suggest that soyfood consumption as part of a healthy balanced diet may lead to a higher breast cancer risk. Even the authors of the study confirm this. It is important to understand that although the study in question has identified some subtle changes in gene expression in a small subgroup of the studied population, the study did not show any link between soy intake on tumour growth, even with such a high intake of soy supplement.

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