Consumption of a Flaxseed-Rich Food is not More Effective than a Placebo in Alleviating the Climacteric Symptoms of Postmenopausal Women

Our objective in this work was to test the effects of daily intake of bread produced with partially defatted ground flaxseed on the climacteric symptoms and endometrial thickness of postmenopausal women. A double-blind, placebo-controlled, randomized clinical trial was performed with 38 women who had been postmenopausal for 1 to 10 y and consumed 2 slices of bread containing 25 g of flaxseed (46 mg lignans) or wheat bran (1 mg lignans; control) every day for 12 consecutive weeks. The outcome variables were the daily number of hot flashes, the Kupperman Menopausal Index (KMI), and endometrial thickness. The plasma lipid profile (total cholesterol and HDL, LDL, and VLDL cholesterol fractions and triglycerides) and the hormones estradiol, follicle-stimulating hormone, thyroid-stimulating hormone, and free thyroxine  also were measured. Food intake was evaluated by means of 2 24-h recalls, before and after the treatment. Twenty patients in the study group and 18 in the control group completed the study. The general characteristics did not differ between the 2 groups at the start of the study. Both had significant, but similar, reductions in hot flashes and KMI after 3 mo of treatment. Moreover, endometrial thickness was not affected in either group. Our findings clearly show that although flaxseed is safe, its consumption at this level (46 mg lignans/d) is no more effective than placebo for reducing hot flashes and KMI. (Author's abstract)
Some epidemiological studies have shown that symptoms such as hot flashes and sweating are less prevalent and of lower intensity in Asian countries where phytoestrogen rich foods such as soy are consumed.  Among the main types of phytoestrogens are lignans, which are found in high concentrations in flaxseed, and isoflavones, which are abundant in soybeans and their derivatives. The main objective in this study was to test the effects of daily consumption of bread produced with partially defatted ground flaxseed that is rich in lignans on the climacteric symptoms and endometrial thickness of postmenopausal patients. The control group had significant reductions in plasma HDLC and FSH concentrations after the intervention. Although some biological and clinical assays on flaxseed have shown its capacity to reduce total- and LDL-C, this did not occur in the present intervention. Both groups had significant reductions in climacteric symptoms (KMI) and occurrences of hot flashes. The total intake of flaxseed may have been too low and the duration of the study too short, to yield significant results under the experimental conditions. (Editor's comments)