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Soy Safe For Breast Cancer Survivors
– Reported, December 27, 2012
“Determining whether it is safe for breast cancer survivors to eat soy has been one of the big research questions under study and now we know it is safe – the evidence is so consistent,” AICR Nutrition Advisor Karen Collins, MS, RD, CDN, an expert on diet and cancer prevention who worked with AICR to examine the research and develop the materials was quoted saying.
For all cancers, human studies show soy foods do not increase risk and in some cases may even lower it, the review finds. A new study summarizes both current and emerging evidence on soy and cancer risk.
Previous concerns with soy and increased breast cancer risk stem from soy foods’ isoflavones, a group of compounds that in some ways mimic the action of estrogen. High blood levels of estrogen are linked to increased breast cancer risk. These fears were enforced by rodent studies that suggested two isoflavones, genistein and daidzein, led to breast cancer cell growth.
Scientists now know that rodents and most other laboratory animals metabolize soy isoflavones differently than humans. And soy consumption does not lead to increased estrogen levels in humans. Six recent human studies and one major meta-analysis have found that consuming moderate amounts of soy foods does not increase a breast cancer survivor’s risk of recurrence or death.
A moderate amount of soy is one to two standard servings daily of whole soy foods, such as tofu, soy milk and edamame. Studies have demonstrated as many as three servings a day are not associated with increased breast cancer risk.
Some preliminary human studies suggest that soy foods may be most protective among breast cancer survivors who are taking tamoxifen, but this research is ongoing.
For breast cancer risk among cancer-free women, studies on soy consumption either show no link or a slightly protective link to breast cancer. Some research suggests that protective effects may primarily come from consuming soy during childhood and adolescence.
“There are numerous ways in which soy foods may protect against cancer. Laboratory studies show that soy isoflavones inhibit a number of cell signaling pathways linked to cancer growth. And research suggests some individuals may benefit more from soy’s compounds than others, Collins was quoted saying.
AICR estimates that 38 percent of US breast cancer cases every year – approximately 86,000 cases – could be prevented if women were to maintain a healthy weight, be physically active, drink less alcohol and breastfeed their children.
To reduce risk of recurrence and secondary cancers, survivors are encouraged to follow these same recommendations.
Soy foods are among the many plant-based foods that can help women get to and stay a healthy weight, note AICR experts.
“The evidence is not quite there to start saying soy reduces the risk of cancer. But for breast cancer survivors who want to eat less meat, get protein and enjoy a more plant-based diet, soy is a healthy food and everyone – including breast cancer survivors – can feel comfortable eating it, Collins concluded.
Source: American Institute for Cancer Research (AICR), December 2012