Breast cancer is currently the most commonly diagnosed cancer among women in the United States. According to the American Cancer Society (ACS), about one in eight women will eventually be diagnosed with breast cancer. Moreover, a woman’s risk of developing breast cancer increases with age.
Several studies conducted on the effects of flaxseed on chronic diseases like breast cancer found encouraging results, leading to further investigation into the link between breast health and lignans.
Although flaxseed is classified as an omega-3, it is also high in lignans, a compound found naturally in various food sources, including flaxseed. Lignans are phytoestrogens. This means they can act like estrogen in the body but are much weaker. Phytoestrogens' ability to inhibit estrogen synthesis and metabolism may be especially helpful in preventing breast cancer and reducing the proliferation of cancer cells.
Studies and Research Involving Breast Health and Lignans
Some studies have shown that women with high levels of lignans in their bodies, as measured from urine and/or blood samples, have a reduced rate of breast cancer. Other studies show insignificant differences. Lignans are common in fruits and vegetables, with flaxseed having the highest levels in food. (1) These studies do not mention any particular brand names of Lignans, and some of the studies indicate that the source of the lignans is the high dietary intake of lignans from fruits and vegetables. Supplementation of lignans may not necessarily produce the same results.
The effects of estrogen are produced when they bind to estrogen receptors inside cells. Like estrogens, phytoestrogens also bind to estrogen receptors. They may also block the effects of estrogen in some tissues but have weaker estrogenic activity than endogenous estrogens (1). Estrogen receptors are present in the reproductive system and numerous other tissues in the human body, including bone, liver, heart, and brain (2). Studies indicate that lignans benefit not only the reproductive system but also these other tissues.
Two types of lignans, Hydroxymatairesinol (HMR) and secoisolariciresinol (SDG), are plant estrogens that get converted to mammalian phytoestrogens. The mammalian phytoestrogens enterodiol (END) and enterolactone (ENL) are produced in the colon by the action of bacteria on the plant precursors matairesinol (MAT), secoisolariciresinol (SECO), their glycosides (HMR and SDG), and other precursors in the diet.
Both END and ENL have been shown to possess weakly estrogenic and antiestrogenic activities. It has been suggested that the high production of these antiestrogenic mammalian lignans in the gut may protect against breast cancer in women and prostate cancer in men. Various in vitro experiments suggested END and ENL significantly inhibited the growth of human colon tumor cells, and enterolactone inhibited the proliferation of breast cancer cells caused by E2. The protective effects of mammalian lignans may be due to their ability to compete with E2 for the type II estrogen receptor, induce sex hormone binding globulin (SHBG), inhibit placental aromatase, and act as antioxidants. (3)
To Summarize, lignans work in 5 different ways to possibly reduce the risk of breast cancer:
1. Lignans bind to estrogen receptors causing endogenous or naturally occurring estrogen from having a place to act.
2. Lignans induce Sex Hormone Binding Globulin (SHBG). More SHBG ties up more estrogen.
3. Lignans are high in antioxidants. The highest of all fruits and vegetables. Antioxidants attack free radicals, which can be responsible for certain types of cancers.
4. Lignans block aromatase enzymes responsible for some estrogen production.
5. Breast cancer actually needs estrogen to grow. With diminished estrogen, cancer cells may start to die.
1) A recent French study conducted over seven years with 58,049 women participants concluded that “High dietary intakes of plant lignans were associated with reduced risks of breast cancer in a Western population that does not consume a diet rich in soy.” Published Journal National Cancer Institute 2007;99:475-86. Touilland, Thiebout, et al.
2) There is a substantial reduction in breast cancer risk among women with a high intake (as measured by excretion) of phyto-oestrogens – particularly the isoflavonic phyto-oestrogens equol and the lignan enterolactone. These findings could be important in the prevention of breast cancer. Ingram D Sanders K Kolybaba M Lopez D Case-control study of phyto-oestrogens and breast cancer In: Lancet (1997 Oct 4) 350 (9083):990 4
3.) PUBMED NLM Wang LQ..Department of Medicinal Chemistry, College of Pharmacy, University of Florida.
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