A new meta-analysis suggests that compounds found in soy and other plant sources, such as isoflavones, might play a significant role in reducing the risk of breast cancer recurrence or death.
This comprehensive review, which included 22 observational studies, sheds light on the potential benefits of plant-derived compounds on breast cancer outcomes.
The research team, comprised of investigators from Australia, Denmark, England, Norway, and the US, focused on the dietary intake of soybeans, lignans (found in seeds, nuts, and various plants), cruciferous vegetables (like cabbage), and green tea.
They specifically examined these foods’ phytonutrients and their effects on breast cancer recurrence, mortality, and all-cause mortality.
Key findings from the study include:
Soy Isoflavones: Soy isoflavones showed a notable association with a 26% reduced risk of breast cancer recurrence. This effect was particularly significant among post-menopausal survivors.
The risk reduction was greatest at a daily intake of around 60 milligrams, roughly equivalent to two to three servings of soy-based products. However, the impact on mortality risk was less pronounced and not statistically significant.
Enterolactone from Lignans: Enterolactone, a compound formed in the gut from lignans, was linked to a 28% reduction in breast cancer-specific mortality and a 31% decrease in all-cause mortality, especially in post-menopausal women.
Lignans are present in flaxseeds, cashew nuts, broccoli, brussels sprouts, and other plant sources. However, determining an effective dietary dose of lignans is challenging due to individual differences in gut microbiome composition.
Green Tea: The consumption of green tea was found to potentially reduce the risk of breast cancer recurrence by 44% in women with stage I or II breast cancer.
The most significant effects were observed with the intake of three to five cups per day, based on two studies from Japan.
Lignans Before Diagnosis: Pre-diagnosis consumption of lignans showed a non-significant risk reduction in cancer-specific mortality in post-menopausal women, but an increased risk in pre-menopausal women, suggesting hormonal factors may influence the effect.
Cruciferous Vegetables: The impact of cruciferous vegetables on breast cancer outcomes was inconclusive, possibly due to low average intake in the studies.
The review also explored whether the timing of consumption (before or after breast cancer diagnosis) affected the outcomes.
However, the data was not definitive, with most studies on green tea and lignans focusing on pre-diagnosis intake, while soy studies included both pre- and post-diagnosis data.
Lead author Diana van Die of the NICM Health Research Institute at Western Sydney University, Australia, graded these findings as probable, indicating strong research evidence.
However, senior author Channing Paller, an associate professor of oncology at Johns Hopkins University, emphasizes that these foods and phytonutrients should complement, not replace, medical and surgical treatment for breast cancer.
This research, published in the journal JNCI Cancer Spectrum, underscores the potential of plant-based compounds in aiding breast cancer survival and highlights the need for more detailed studies to establish effective dosages and the impact of consumption post-diagnosis.
It offers hope and guidance for patients seeking to enhance their diet as part of a comprehensive treatment strategy.
If you care about breast cancer, please read studies about a major cause of deadly breast cancer, and common blood pressure drugs may increase death risk in breast cancer.
For more information about cancer, please see recent studies that new cancer treatment could reawaken the immune system, and results showing vitamin D can cut cancer death risk.
The research findings can be found in the journal JNCI Cancer Spectrum.
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