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Flaxseed Ineffective in Controlling Hot Flashes

Jonathan S. Batchelor
Published: Thursday, Aug 25, 2011
Sandhya Pruthi, MD, PhD

Sandhya Pruthi, MD, PhD

Flaxseed had no effect on reducing hot flashes in postmenopausal women who reported experiencing 28 or more hot flashes per week, according to the results of a randomized phase III trial of women with and without breast cancer presented at the ASCO meeting in June.

About half of the women in the study had a history of breast cancer and the other half did not. The researchers noted that hot flashes are a common symptom during the menopause transition or following breast cancer treatment that can negatively impact the quality of life for many women. Flaxseed contains compounds that were suspected of being able to mitigate hot flashes.

“The results were surprising. Pilot study data suggested that flaxseed use was associated with [a] reduction in hot flashes,” noted lead author Sandhya Pruthi, MD, PhD, associate professor of medicine at the Mayo Clinic in Rochester, Minnesota, and a researcher with the North Central Cancer Treatment Group in Rochester. “Flaxseed may be a highly touted supplement for many ills, but according to our randomized study results, it is not effective for hot flashes.”

A cohort of 188 postmenopausal women were randomly assigned to eat a daily flaxseed bar that contained 410 mg of lignans, a plant-based compound known to have both estrogenic and antiestrogenic effects (88 women), or placebo, a bar made of protein and fiber without flaxseed or lignans (90 women), for 6 weeks. Of the 178 evaluable women in the study, 91 had a history of breast cancer while 87 did not.

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Participants completed daily prospective, selfreport hot flash diaries during the baseline week and then began eating 1 study bar per day for 6 weeks, while continuing to record their daily hot flashes. The intra-patient difference in hot flash activity between baseline and the last treatment week was the primary endpoint. Gastrointestinal side effects reported by both groups were most likely due to the fiber content in the flaxseed and placebo bars, the researchers reported.

“What we were surprised to find was that the flaxseed did not work any differently than the placebo in reducing hot flashes,” noted Pruthi. “Approximately one-third of the participants on the flaxseed and the placebo had about a 50% reduction in their hot flashes, so really no significant difference.”

The “disappointing” randomized trial results showed why clinical trials are necessary, observed Mark G. Kris, MD, chief of the Thoracic Oncology Service and The William and Joy Ruane Chair in Thoracic Oncology at Memorial Sloan-Kettering Cancer Center in New York City, moderator of the press conference at which the results were unveiled.

“That’s what our patients deserve,” he said. “They need to know they are getting an effective therapy.”

“Patients shouldn’t necessarily give up on flaxseed,” counseled Pruthi. “Although our results found that flaxseed does not reduce hot flashes, there may be other health benefits.”


Pruthi S, Qin R, Terstriep SA, et. al. The evaluation of flaxseed for hot flashes: results of a randomized, controlled trial, NCCTG study N08C7. J Clin Oncol. 2011;29(suppl; abstr CRA9015).



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