What are lignans?
Lignans are phytonutrients found in a wide variety of foods such as, flaxseed, whole grains, beans, legumes, fruits and vegetables. They are actually the components in these plants that develop into the hard outer tissue, known as lignin tissue. Our intestines convert lignan-rich foods into beneficial hormone-like compounds, phytoestrogens. (Although this conversion is blocked if you take antibiotics or have a high fat diet.) Flaxseed contains 75-800 times more lignans than any other plant.
Lignans are concentrated in the following foods:
Flaxseeds*, peanuts and caraway seeds; broccoli, garlic, carrots, lentils, soybeans and kidney beans; cranberry, strawberry, raspberry, banana, guava and cantaloupe; barley, rye and oats.
*Important to note that most flaxseed lignans are removed during the processing of seeds to oil, so they are generally not found in any great degree in flaxseed oil.
The most important lignan in flaxseed is secoisolariciresinol diglycoside, but we shall refer to it by its much simpler form, SDG. When eaten SDG in flaxseed is converted by bacteria in the colon to the mammalian lignans-enterolactone and enterodiol. This conversion is crucial as it is only in this form that lignans have beneficial effects for human health.
Benefits of lignans
Lignans have many biological properties, the most significant being that they are phytoestrogens, have potent antioxidant properties and are believed to be chemoprotective. This means they have beneficial roles to play in a variety of health issues ranging from a whole host of menopausal symptoms; breast disease; osteoporosis, and prostate enlargement, to heart disease, acne and hypercholesterolemia.
Because lignans are high in plant oestrogens, they have a plethora of positive roles to play in women’s health issues. Oestrogen levels are typically high in women during the childbearing years and then fall away through the peri-menopausal and post-menopausal years. While lignans have an oestrogen-like action, they are considerably weaker that our endogenous oestrogen, and act as hormone balancers. An important feature of these plant hormones is that they do not stimulate reproductive tissue. In conditions which are linked with excess oestrogen (such as PMS, unhealthy breast tissue and breast cancer) lignans compete with a woman’s own oestrogen, having an oestrogenic- lowering effect. Studies have shown that urinary excretion of mammalian lignans is frequently lower in breast cancer patients than in normal healthy postmenopausal women, suggesting that lignans may have a protective effect against breast cancer. In a randomized, double-blinded placebo-controlled trial of 39 women with newly diagnosed breast cancer, patients received 25 gms flaxseed or placebo daily for just over a month before surgery. The patients who received flaxseed meal had decreased tumor cell proliferation rate similar to the effects seen with the breast cancer drug,Tamoxifen.
In conditions associated with declining oestrogen levels such as menopause, lignans have the opposite effect, increasing levels of oestrogen. This balancing action is due to their ability to competitively lock onto our body’s oestrogen receptor sites. Consequently, lignans are used to reduce symptoms of menopause, such as hot flushes, night sweats, mood swings and breast tenderness. Other conditions where lignans may be helpful due to their ostrogenic effect includes bone health, prostate conditions, hair loss and acne.
Hormone deficiency is a well know risk factor for osteoporosis in postmenopausal women.Oestrogen plays an important role in maintaining bone density by regulating the formation and resorption of bone. As phytoestrogens lignans may be an additional natural alternative for women with poor bone density. Some clinical studies suggest that these plant compounds are somewhat effective in maintaining bone mineral density, sharing a similar chemical structure with endogenous ostrogen. However further research and longer term studies need to be carried out in this area.
In the body testosterone is converted to a more potent form called dihydrotestosterone (DHT). Although normal healthy prostate cells require DHT for growth, too much of it can cause abnormal growth, leading to an enlarged prostate or causing prostate cancer cells to divide. Researchers have found that concentrations of lignans are higher in the urine and prostatic fluid of populations that have a lower risk of prostate cancer. In a Danish study undertaken in 2001, patients with newly diagnosed prostate cancer who supplemented their diets with 30 g flaxseed from the time of diagnosis to time of surgery, saw a significant reduction in tumor proliferation index, free androgen index, total serum testosterone and total cholesterol, and an increase in tumor apoptosis index (tumor cell death). Lignans may therefore play a role in influencing the metabolism of testosterone and its metabolites. It is thought that lignans can block the action of the enzyme 5 alpha-reductase that converts testosterone into the more potent form of DHT.Lignans may also reduce the amount of testosterone available due to their ability to increase sex hormone binding globulin (SHBG). This protein binds circulating testosterone, making less testosterone available to stimulate prostate cell growth.
In addition to being a phytoestrogen, SDG the plant lignan isolated in flaxseed, is also a strong antioxidant. (Antioxidants are associated with a reduced risk of atherosclerosis).The antioxidant SDG is also metabolized to secoisolariciresinol (SECO), enterodiol(ED) and enterolactone (EL). These metabolites have three times more antioxidant potency than their precursor SDG and up to five times more potency than vitamin E. Furthermore, studies have repeatedly shown that the fibre and fatty acids found in flaxseeds (not to mention the lignans), when taken daily can reduce both total and LDL(low density lipoprotein) cholesterol levels significantly. The flax lignan can furthermore, additionally reduce cholesterol deposits and plaque on artery walls by as much as 73 per cent.
Hormone-generated acne may benefit from a diet rich in lignans. (While the cause of acne is not totally understood, hormones, bacteria, heredity and stress are all thought to be contributing factors). During puberty, the production of adrenal androgens is increased in both males and females. This elevation of androgens can cause a corresponding increase in sebum production, especially in the face, chest and back. Excess sebum leads to acne. Since androgens (testosterone) play a major role in acne, lignans may have a positive role to play in its treatment. Lignans have been shown to inhibit 5 alpha-reductase, (the enzyme involved in the conversion of testosterone to DHT), and inhibition of this enzyme is often successful in the treatment of androgen-dependant disorders.
One of the most common forms of hair loss or alopecia is androgenetic alopecia. (AGA).It is believed that an individual’s level of androgens -testosterone and its metabolites-is one factor in AGA. As we have seen in our discussion of prostate health, lignans have also been shown to be effective in inhibiting 5 alpha-reductase and other enzymes involved in the metabolism of testosterone. Therefore lignans clearly have a role to play in the treatment of hormone dependant hair loss.
Recommended therapeutic dose
Although there are not yet any set guidelines for lignan intake, a sensible amount would be to aim for be approximately 50 -150mg per day.*
This translates to one tablespoon of flaxseed meal daily (each rounded tablespoon equals 10 grams linseed meal which provides approx 50-150 mg of lignans), plus a diet rich in whole grains particularly barley and rye, legumes- think soybeans, vegetables-emphasize broccoli and carrots, and fruits, particularly strawberries and cranberries. Now that’s no hardship! We are fortunate to have a wide and delicious array of naturally occurring lignans available to us all year round. The plant kingdom never lets us down.
*It is important to note however that very few studies have been conducted examing the effect of lignans in pregnant and breastfeeding women, as well as in young children or women being treated for breast, uterine or ovarian cancer. Therefore until further definitive studies are conducted, lignans cannot be recommended for these groups.
The grains are best left to soak overnight but even a half hour soak will still provide delicious results
1 cup rolled rye flakes
½ cup barley flakes
½ cup rolled oats
1 cup linseed meal
1 ½ cups water
2 cups raspberries, blueberries and strawberries
1 tablespoon toasted sesame seeds
Tahini to taste
Soak rye, oats and barley in the water overnight. Add the linseed meal and sesame seeds. Mix raspberries, blueberries and strawberries together. Add to the oats and barley. Drizzle with tahini and serve with soy yoghurt or soy milk.
Thompson, L. U et al. “Biological effects of dietary flaxseed in patients with breast cancer” Breast Cancer Res Treat. (2000) p50
Evans, B.A. et al “Inhibition of 5 alpha-reductase in genital skin fibroblasts and prostate tissue by dietary lignans and isoflavonoids” J.of Endocrinolgy (1995) Vol. 147 pp295-300
Haggans, C.J., et al. Effects of flaxseed consumption on urinary oestrogen metabolites in postmenopausal women “Nutr Cancer (1999) Vol 33 pp 188-194
Chen J Wang L, Thompson LU .Flaxseed and its components reduce metastasis. Cancer Lett. 2005 May 20
Brooks J. et al “Supplementation of flaxseed alters oestrogen metabolism in postmenopausal women Am. J. of Clin Nutr. 2004 70: 318-325
Mazur W, Phytoestrogen content in foods. Bailierre’s Clin Endocrine Metab 12:729-740 1998
Int. J. Cancer 2005 Sept.20 116 (5)
J. Clin Endocrin. Metab. 2002; 87(4) Flaxseed improves lipid profile without altering biomarkers of bone metabolism
J.Endocrinolgy 1995 Nov. 147(2(:295-302
Mol. Cell Biochem 1999 202 91-100
Nutr. Rev 2004 Jan 62 (1) 18-27
Urology 2005 May 63(5) 900-902
www.totalhealthmagazine.com “Special report on Lignans”
www.elsevier.com/loacat/phytochem 2004. 03.005