Flaxseed Dims Hot Flashes in Postmenopausal Women

ROCHESTER, Minn., Aug. 30 -- A daily dose of crushed flaxseed halved hot flashes in postmenopausal women who did not want to take estrogen, according to a pilot study.
After six weeks of therapy, the mean reduction in daily hot flash frequency went from 7.3 to 3.6, Sandhya Pruthi, M.D., of the Mayo Clinic, and colleagues, reported in the summer 2007 issue of the Journal of the Society for Integrative Oncology. This represented a mean reduction of 50% and a median reduction of 50% (P<0.001), the researchers said.
The weak estrogenic properties in flaxseed seem to be the most likely mechanism of the plant's effectiveness, Dr. Pruthi said.
Effective nonhormonal therapies for hot flashes include antidepressants, such as venlafaxine (Effexor) and gabapentin (Neurontin), but not all women benefit from these agents, and toxicities may limit their use, the researchers said.
Clinical trials evaluating herbal and dietary supplements, including vitamin E, black cohosh, and soy, as well as acupuncture, have not shown convincingly that these agents outdo placebo.
Flaxseed, also known as linseed, is another popular supplement that has not been well studied for hot flashes, the researchers said.
Considered a phytoestrogen, fiber-rich flaxseed is a rich source of lignans and omega-3 fatty acids. Lignans have antioxidant properties and are thought to have estrogen agonist and antagonist properties, such as those in selective estrogen receptor modulators, such as tamoxifen, they said.
Research findings also suggest that dietary lignans have some cancer-protective effects. Therefore, Dr. Pruthi said, flaxseed is an interesting agent to study for managing vasomotor symptoms.
In the six-week study of 30 women enrolled from June 17 to Nov. 8, 2005, 23 women completed the study. Twenty-one provided complete information.
The women recorded daily hot flashes in a diary and, once a week, completed a symptom questionnaire evaluating nausea, excessive sweating, joint or muscle pain, chills, headache, nervousness, and negative mood swings.
To be enrolled, the women reported at least 14 hot flashes per week for at least one month. In the preceding four weeks, the participants had not received chemotherapy, androgen, hormonal agents, or other herbal supplements, including soy.
In the baseline week, participants took no study medication and documented the characteristics of their hot flashes. Thereafter, they took 40 g daily of crushed flaxseed.
Flaxseed, provided in a fine granulated powder, contained 26% dietary fiber, 40% triglycerides, and 1% secoisolariciresinol diglucoside (a lignan antioxidant). The high-fiber product made from flaxseed hulls provided a large percentage of lignans.
In the last week of flaxseed therapy, the mean decrease in hot flash scores was 57%, and the median decrease was 62%.
The mean number of hot flashes reported by the participants at baseline was 7.3 per day, which, after six weeks of flaxseed therapy, had decreased to 3.6 per day.
Side effect analysis revealed that 14 (50%) of the participants had abdominal distention or bloating at some time during the trial.
Of these, 12 had mild distention and two moderate distention. Eight women reported mild diarrhea, one had moderate flatulence, two had moderate headache, and one had a mild hypersensitivity reaction.
Six women (21%) did not complete all six weeks of the therapy, three because of abdominal toxicities, one because of weight gain, one because of taste intolerance, and one for unspecified reasons.
Statistically significant improvements were reported for mood, joint or muscle pain, chills, and sweating. Quality of life improved, and the women reported less anger, anxiety, and fatigue on the Self-Assessment Scale.
However, these preliminary results need to be evaluated in a larger, placebo-controlled trial, Dr. Pruthi added.
As an example, the authors pointed out that in a similar pilot trial evaluating black cohosh reported a reduction in hot flash score (frequency and severity) that exceeded 50%. A large randomized placebo-controlled study was subsequently initiated, and failed to provide evidence that black cohosh reduced hot flashes more than placebo.
Because of the various abdominal toxicities, it is possible that initiating flaxseed therapy at a lower dose and titrating the dose upward might decrease abdominal toxicities, the researchers suggested.
No financial disclosures were reported. This trial was funded by the Susan B. Komen Breast Cancer Foundation.Primary source: Journal of the Society for Integrative OncologySource reference: Pruthi S, et al "Pilot Evaluation of Flaxseed for the Management of Hot Flashes" J Soc for Integrative Oncology 2007; 5: doi 10.2310/7200.2007.007.