Flax is a versatile plant: its fibrous body has been used to make rope, clothing and nets, while its seeds and oil are used in cooking and baking and as a dietary supplement. Flaxseed has been studied for its effect on hormonal symptoms in women like menstrual cramps, menopause and hormone-induced cancers. Scientific studies on the subject are, however, inconclusive.
Flaxseed
The omega-3 essential fatty acids docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA, are found only in fish oils, while alpha-linolenic acid, or ALA, is present in plant sources like flaxseed oil. Although DHA and EPA are the most potent anti-inflammatory and heart-protecting omega-3s, the ALA found in flaxseed may have similar, though less pronounced, effects. The University of Maryland Medical Center found that studies on flaxseed supplementation show it may be effective against high cholesterol, heart disease, menopause and colon, prostate and skin cancer. Studies are inconclusive on its use against ADHD, migraines, lupus, ulcers and more. Flaxseed is also a potent bulk-forming laxative, and its oil can be used to soothe dry and irritated skin.
Lignans and Cancer
The effects of flaxseed on hormone-induced breast, endometrial and ovarian cancer in women have been studied extensively. Scientists believe that its effectiveness in these areas may be connected to lignans, or "phytoestrogens" -- plant-based compounds present in flaxseed that mimic the action and effects of estrogen in the body. The Linus Pauling Institute of Oregon State University reports that the data on lignans and breast cancer risk conflict strongly enough to render them inconclusive. Other studies have found a connection between lignan intake and decreased incidence of endometrial and ovarian cancer in postmenopausal women, but it is not known whether this is due to a single source of lignans like flaxseed or an overall healthier plant-based diet. If you or your family has a history of cancer, speak with your doctor before supplementing with flaxseeds.
Menstruation and Menopause
Flaxseed has been studied as a treatment for women's hormonal issues, from symptoms of menopause like hot flashes and vaginal dryness to menstrual pain and PMS. Although anecdotal evidence for its efficacy abounds, a placebo-controlled year-long study published in the "Journal of Clinical Endocrinology and Metabolism" in 2004 showed flaxseed to be no more effective against symptoms like hot flashes than wheat germ. In 1996, a study in the "American Journal of Obstetrics and Gynecology" showed that another type of omega-3 supplement, fish oil, decreased menstrual cramps in adolescent girls. However, fish oil contains the omega-3s DHA and EPA, not ALA, like flaxseed. There is no evidence showing a similar effect from flaxseed supplements.
Dosage and Warnings
The typical adult dose for flaxseed oil is 1 to 2 tbsp. twice daily. For constipation, start with 5 g of crushed or whole flaxseeds in water three times a day. The National Institutes of Health caution not to take flaxseed oil while taking blood-thinning medications or medication for high blood pressure, since flaxseed can exacerbate these effects. It may also alter the effectiveness of oral contraceptives and diabetes medications. There is also evidence that flaxseed does influence female hormones -- for instance, a 1998 study published in the "Journal of Nutrition" found that pregnant rats fed large amounts of flaxseed gave birth to rats with reproductive abnormalities. Until this type of effect is better understood, pregnant or nursing women should avoid eating large amounts of flaxseed.
References
- University of Maryland Medical Center; Omega-3 Fatty Acids; Steven D. Ehrlich; 2009
- Mayo Clinic; Omega-3 Fatty Acids, Fish Oil, Alpha-Linolenic Acid; 2011
- National Institutes of Health; MedlinePlus: Flaxseed Oil; 2011
- University of Maryland Medical Center; Flaxseed; Steven D. Ehrlich; 2009
- Linus Pauling Institute; Lignans; Jane Higdon; 2005
- Langone Medical Center; Flaxseed; 2011
