Lignans

Lignans are polyphenols found in plants having health benefits as precursors to phytoestrogens and exerting positive effects on lipid profiles.  Lignan precursors are high in a wide variety of plant-based foods – including seeds (superlatively high amounts are found in flaxseeds, also high in sesame seeds, but not their oil), whole grains, legumes, fruit, and vegetables. Lignans are the principal source of dietary phytoestrogens in the typical Western diets

Phytoestrogens (plant estrogens) have a structure similar to the steroidal estrogen hormones.  Estrogen is a hormone in the body, which exerts its effect by binding to estrogen receptors on cells of numerous body tissues, including those associated with reproduction, or those in bone, lungs, liver, heart and brain. Estrogen dominance is a significant problem today as we are immersed in a “sea” of estrogens. Phytoestrogens have a weaker effect than endogenous estrogen, and so may block or antagonize estrogen, but they still do have an estrogenic effect, which may be tissue specific. For example, an anti-estrogenic effect could reduce risk of reproductive organ cancers, whilst a weak estrogenic effect could increase bone density and reduce osteoporosis. A topic of current research.

Additionally, independent of effects on estrogen receptors, phytoestrogens may change estrogen activity by altering the activity of enzymes involved in estrogen metabolism Pubmed

Phytoestrogens include:

• Plant lignans: Secoisolariciresinol diglucoside (SDG), in flax and sesame seeds, grains, vegetables;
• Isoflavones: genistein and daidzein, in soy, mung beans, alfalfa.
• Coumestans: in sprouts of alfalfa, clover, mung and soybeans.

Secoisolariciresinol diglucoside (SDG) is the predominant plant lignan /phytoestrogen in flaxseed (found mainly in the flaxseed hull; others in small amounts are pinoresinol, lariciresinol and matairesinol).   After ingestion, intestinal microflora convert SDG to another plant lignan, called SECO (secoisolariciresinol), Considered an essential lignan, SECO is further metabolized to the mammalian lignans enterodiol (END) and enterolactone (ENT) by intestinal bacteria. END and ENT from SDG (and the other plant lignans) are absorbed from the intestinal lumen into the bloodstream. END can also be converted to ENT by intestinal bacteria. END and ENT bioavailability is improved by first grinding the flaxseed.

Studies conclude that SDG, and its metabolites, END and ENT, sport the following impressive effects:

• Lignans enterodiol (END) and enterolactone (ENT) have weak estrogenic activity and may have a role in hormone-related cancers (breast, uterine, ovarian, and prostate), heart disease and osteoporosis (estrogen improves bone density); Oregon state article. The bioactive form of enterolignan is enterolactone, which binds to estrogen receptors to either block or amplify estrogen. Phytoestrogens have a less stimulating effect on these receptors than estrogen and so temper effects of more strongly stimulating estrogens.
• Antioxidant – property attributed to benefits seen in cancer, CVD, lupus nephritis, and diabetes. Prevents DNA oxidative damage, lipid peroxidation, and oxidative stress related to metabolic syndrome, and is involved in hypocholesterolemic and antiatherogenic effects.
• Anti-inflammatory
• Antiviral, antibacterial, anti-fungal
• Both anti-estrogenic and estrogenic
• Anti-hormone-related-cancer – by preventing pre-cancerous cellular changes and reducing angiogenesis and metastasis, due to strong antiproliferative, antioxidant, antiestrogenic, and/or antiangiogenic activities. Pubmed High dose phytoestrogen significantly reduced risk of breast cancer in post-menopausal women. Pubmed
• Anti-diabetic /metabolic syndrome – by reducing lipid and glucose concentrations.
• Anti-atherogenic / CVD – by lowering total cholesterol, LDL-cholesterol (LDL-C) and triglycerides, and normalizing HDL-cholesterol (HDL-C), decreasing blood pressure, oxidative stress and inflammation, and inhibiting platelet aggregation in patients with dyslipidemia. Also inhibiting arrythmias.  Yang et al, 2021

Flaxseed is “hands down” the richest food source of plant lignans!   Other food sources of plant lignans, include seeds (sesame, pumpkin, sunflower, poppy), whole grains (rye, oats, barley), bran (wheat, oat, rye), beans, fruit (especially berries), vegetables, and beverages such as tea, coffee, and wine. However, 1 tablespoon flaxseed contains about 3-4 times the next highest sources (by serving size), namely 1T sesame seeds, 1/2 Cup peas, or 1T chickpeas, and about 100 times or more the next highest sources of 1 Cup whole grain rye or oats, or a 5 oz glass of wine.

• Flax meal reduced TESTOSTERONE in prostate cancer patients – Researchers at Duke University found that supplementation with ~ 1 oz milled flax combined with low fat diet over ~1 month resulted in significant decreases in both total and free TESTOSTERONE in prostate cancer patients. They also found a decrease in PSA levels in men with early stage prostate cancer. A later Duke University study supplementing flaxmeal over 6 months in men with enlarged prostate significantly lowered PSA levels and decreased benign epithelium proliferation rates, but interestingly did not significantly alter TESTOSTERONE levels.

Kezimana et al, 2018