Consuming soy foods such as soy milk and tofu and cruciferous vegetables such as cabbages, kale and broccoli may help reduce common side effects of treatment in breast cancer survivors, researchers say.
Treatments designed to prevent breast cancer recurrence often inhibit the body's production or use of oestrogen - the hormone that can fuel breast cancer growth.
As a result, such patients often experience hot flushes and night sweats, among other side effects that are commonly post menopause.
The findings, led by researchers from Georgetown University, showed that intake of cruciferous vegetables and soy foods were associated with fewer reports of menopausal symptoms.
Higher soy intake was also associated with less reported fatigue.
Phytochemicals, or bioactive food components, such as isoflavones in soy foods and glucosinolates in cruciferous vegetables may be the source of the benefit, the researchers said.
While isoflavones bind to oestrogen receptors and exert weak oestrogenic effects, glucosinolates in cruciferous vegetables influence levels of metabolising enzymes that can modulate inflammation and levels of oestrogen, possibly attenuating treatment-related symptoms.
The study addresses an important gap in research on the possible role of lifestyle factors, such as dietary habits, in relation to side effects of treatments, said lead author Sarah Oppeneer Nomura from the University's Georgetown Lombardi Comprehensive Cancer Center.
"These symptoms can adversely impact survivors' quality of life and can lead them to stopping ongoing treatments," Nomura said.
"Understanding the role of life style factors is important because diet can serve as a modifiable target for possibly reducing symptoms among breast cancer survivors," she added.
For the study, published in Breast Cancer Research and Treatment, the team included 173 non-Hispanic white and 192 Chinese Americans.
Women who consumed more soy foods also showed suggestive associations with lower reporting of other symptoms, including joint problems, hair thinning/loss and memory, but these associations did not reach statistical significance.
Thus, until more study is conducted, breast cancer patients should not suddenly start eating soy, if they have not consumed it before, the researchers warned.