In a recent communication on LinkedIn, Kefah Mokbel, who chairs Breast Cancer Surgery at The London Breast Institute, addressed a significant concern among women diagnosed with breast cancer regarding the consumption of soy products. He stated:
“Soy after breast cancer: should women really avoid it? New evidence offers reassurance.”
This remark underscores an ongoing debate about phytoestrogens—naturally occurring substances found in foods like soy and flaxseed. These compounds can interact with estrogen receptors, raising concerns about potential effects on estrogen levels and breast cancer recurrence.
Recent Research Findings
A systematic review recently published has shed light on this topic, analyzing data from randomized controlled trials that included four separate studies and a total of 1,698 women diagnosed with breast cancer.
Key Discoveries
- The review found no evidence suggesting that the intake of phytoestrogens is associated with a higher risk of breast cancer recurrence.
- Additionally, there were no significant increases in circulating estrogen levels observed among participants. Some studies even indicated a trend toward decreased estrogen concentrations, although these differences did not reach statistical significance.
- Notably, one smaller trial with 19 women did report a significant decline in estrone levels.
Limitations and Future Directions
Despite these reassuring findings, the authors of the review caution that the body of evidence remains limited. Only one of the studies specifically examined breast cancer recurrence, none tracked mortality outcomes, and several hormonal studies involved small sample sizes. As such, the researchers emphasize the need for additional large-scale, long-term randomized trials to draw more conclusive results.
Conclusion
Based on current randomized evidence, there is no justification for advising women with breast cancer to avoid phytoestrogen-rich foods, including soy. However, it is equally important to note that the evidence is insufficient to advocate for phytoestrogen supplements as a method for improving prognosis or preventing recurrence.
This systematic review was conducted by Laurence Poirier and Caroline Diorio. For those interested in further reading, the full findings are available in the review titled: Effects of phytoestrogens on prognosis and hormonal markers of breast cancer: A systematic review of randomized controlled trials.
Additionally, other research findings relevant to breast cancer treatment can provide more insights, such as the study exploring Giredestrant plus Everolimus and its effect on progression-free survival after resistance to CDK4/6 inhibitors.
