Breast cancer cell proliferation did not decline with the use of soy isoflavone supplements in a randomized clinical trial, according to a study published in Cancer Prevention Research, a journal of the American Association for Cancer Research.
These study results are compatible with the findings of previous studies designed to test dietary supplements and their cancer prevention benefits, said lead researcher Seema A. Khan, MD, professor of surgery at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University.
“Simply put, supplements are not food. Although soy-based foods appear to have a protective effect, we are not seeing the same effect with supplementation using isolated components of soy, so the continued testing of soy supplements is likely not worthwhile,” said Khan.
For the study, 98 women were assigned either a mixed soy isoflavones supplement or placebo. More than 4000 breast cancer epithelial cells were identified in these women by fine-needle aspiration biopsy. After 6 months, the levels of Ki-67, an established protein marker of cancer cell growth, were evaluated. Results showed no differences across the overall population after 6 months in either the supplement or the placebo group. However, among premenopausal women, a negative effect of the supplementation was suggested when the level of Ki-67 increased from 1.71 to 2.18.
“This was a small finding, but one that should suggest caution,” said Khan.
Source: AACR.