Flaxseed contains about 1-2% total phenolic compounds of which the lignan secoisolariciresinol diglucoside (SDG) is a major component. Lignans are phytoestrogens that are found in many plants, but flaxseed is the richest source. The predominant lignan in flaxseed is SDG, though small amounts of other lignans are also present, including pinoresinol, lariciresinol, and matairesinol. After ingestion, SDG is converted to mammalian lignans by bacteria in the colon. The first step in the conversion produces secoisolariciresinol (SECO), which is then converted to enterodiol and enterolactone. These lignans are structurally similar to estradiol, the major form of estrogen in the body, which permits their binding to estrogen receptors (1).
The health benefits of SDG are numerous including antioxidant and estrogenic/oestrogenic effects leading to positive effects with respect to cardiovascular diseases, diabetes and menopause.
Flaxseed has been investigated for effects on conditions related to estrogen metabolism. Hot flashes are one of the most common symptoms experienced by women around the time of menopause (2). A systematic review recently assessed the effectiveness of several natural products including flaxseed in alleviating hot flashes. MEDLINE (1966 to January 2015), Scopus (1996 to January 2015), and Cochrane Central Register of Controlled Trials (The Cochrane Library) were searched. Research on flaxseed supplementation indicated an alleviation of the number and severity of hot flashes.
Another recent study compared the therapeutic effect of flaxseed, evening primrose oil, and Vitamin E on the duration of the period of breast pain which is also a common symptom of menopause (3). The research was a quasi-randomized clinical trial conducted in 2015 on ninety patients complaining of breast periodic pain. One group received 30 g of milled flaxseed, the second group received two 1000 mg capsules of evening primrose, and the third group received 1 capsule of 400 IU Vitamin E, daily and for two menstrual cycles. Cyclical breast pain was measured at the beginning and end of both intervention periods by daily subscription form of pain duration. The mean duration of breast pain in flaxseed group within 2 months of intervention decreased significantly. Although there were reductions in the duration of pain in evening primrose oil and Vitamin E groups, neither were significant.
A phase 2 pilot study assessed the effect of 6 weeks of 40 g/day milled flaxseed consumption on hot flash scores in women not wishing to receive estrogen therapy (4). Eligibility included 14 hot flashes per week for at least 1 month and thirty women were enrolled. The mean decrease in hot flash scores after flaxseed was 57% (median decrease was 62%). The mean reduction in daily hot flash frequency was 50% (median reduction 50%), from 7.3 hot flashes to 3.6. This study suggests that flaxseed decreases hot flash activity in women not taking estrogen therapy, a reduction greater than what would be expected with placebo.
In 18 premenopausal women with normal menstrual cycles, eating 10 g of milled flaxseed daily for 3 months lengthened the luteal phase of the menstrual cycle (5). Milled flaxseed fed at a level of 25 g daily for 2 weeks, vaginal cell maturation was stimulated in 25 postmenopausal women, suggesting an estrogenic effect of flaxseed on the reproductive tract.
In another study, twenty-five menopausal women with mild symptoms either ate 40 g of milled flaxseed daily or took an oral estrogen-progesterone hormone replacement (0.625 mg conjugated estrogens per day) for two months (6). After a two-month period free of treatment, each group crossed over to the other intervention for two months. Flaxseed was as effective as hormone replacement therapy in improving mild menopause symptoms.
These results require validation in larger, placebo-controlled trials but do suggest positive outcomes on various menopausal symptoms following flaxseed consumption. The estrogenic properties identified in flaxseed seem to be the most likely mechanism for its effectiveness in reducing menopausal effects.
References
- Adolphe JL, Whiting, SJ, Juurlink, B, et al. Br J Nutr. 2010. 103:929-938.
- Ghazanfarpour, M, Sadeghi, R, Abdolahian, S, Latifnejad Roudsari, R. Int J Reprod Biomed (Yazd). 2016. 14(3): 155–166.
- Jaafarnejad F, Adibmoghaddam E, Emami SA, Saki A. J Educ Health Promot. 2017. 6:85. doi: 10.4103/jehp.jehp_83_16.
- Pruthi, S, Thompson, SL, Novotny, PJ, et al. J. Soc. Int. Oncol. 2007. 5(3): 106–112.
- Phipps, WR, Martini, MC, Lampe, JW, et al. J. Clin. Endocrinol. Metab. 1993. 77:1215-1219.
- Lemay, A, Dodin, S, Kadri, N et al. Obstet. Gynecol. 2004. 100: 495-504.