Some preliminary reports had suggested the plant-based estrogen-like compounds called phytoestrogens in flaxseed might be effective in cooling hot flashes in women.
But this study showed no difference in the number of hot flashes reported by women taking flaxseed vs. those taking a dummy treatment.
"Hot flashes are a common symptom during the menopause transition or following breast cancer treatment," says researcher Sandhya Pruthi, MD, of Mayo Clinic's Breast Diagnostic Clinic, in a news release. "While our preliminary data from our 2007 pilot study showed a reduction in hot flashes associated with the consumption of ground flaxseed, our new study did not result in a significant decrease in hot flashes with eating flaxseed compared to placebo."
The study, presented at the American Society of Clinical Oncology Meeting in Chicago, looked at the effects of flaxseed on hot flash frequency in 188 postmenopausal women and breast cancer patients.
The women were randomly divided into two groups. One group ate a bar containing 410 milligrams of phytoestrogens from ground flaxseed and the other ate a placebo bar for six weeks. Both groups kept a diary of their hot flashes for one week before treatment and throughout the study.
The results showed that in both groups, about a third of the women reported a 50% reduction in hot flashes, and there was no significant difference between the two groups in hot flashes.
Both groups reported side effects related to the fiber content in the bars, such as gas, diarrhea, and nausea.