Lignans are a class of polyphenols found in various plant-based foods, most notably flaxseed and sesame seeds. After ingestion, these plant lignans are metabolized by the intestinal microbiota into enterolignans, primarily enterolactone and enterodiol, which are then absorbed into the body to exert a wide array of physiological effects. Their multifaceted benefits stem from their antioxidant, anti-inflammatory, and phytoestrogenic properties.
The Mechanisms Behind Lignans' Benefits
Gut Microbiota Conversion
In the digestive tract, gut bacteria convert plant lignans, such as secoisolariciresinol diglucoside (SDG) from flaxseed, into their active mammalian forms, enterodiol (ED) and enterolactone (EL). This conversion is essential for absorption and utilization, and an individual's gut microbiome composition can influence its efficiency.
Antioxidant and Anti-inflammatory Action
Lignans act as powerful antioxidants, protecting cells from oxidative stress caused by free radicals. This is important for reducing chronic inflammation, a factor in many diseases like atherosclerosis and neurodegenerative conditions. Lignans help maintain cellular health and reduce inflammation by scavenging hydroxyl radicals and modulating inflammatory pathways.
Key Roles of Lignans in the Body
Hormone Modulation
As phytoestrogens, lignans have a structure similar to estrogen, allowing them to bind to estrogen receptors and help balance hormones.
- For women with high estrogen: Lignans can act as weaker estrogens, competing with stronger endogenous estrogen and potentially reducing the risk of hormone-sensitive cancers.
- For women with low estrogen: Lignans can provide a mild estrogenic effect, potentially easing menopausal symptoms like hot flashes.
- For men: Lignans may support prostate health by influencing the balance of testosterone and DHT.
Cardiovascular Health
Lignan intake is linked to a lower risk of cardiovascular disease. Their benefits include:
- Cholesterol Reduction: Fiber and lignans in foods like flaxseed can lower LDL cholesterol by binding to bile acids. This is associated with a lower risk of heart attacks and strokes.
- Blood Pressure Management: Lignans may also help lower blood pressure, a major heart disease risk factor.
- Reducing Arterial Inflammation: The anti-inflammatory effects of lignans can help reduce plaque-contributing inflammation in arteries.
Cancer Prevention
Research explores lignans' potential in preventing cancers, especially hormone-sensitive ones like breast, prostate, and colorectal cancers. Their anti-estrogenic and antioxidant effects might inhibit cancer cell growth, though more human research is needed.
Digestive Health
Lignan-rich foods, particularly flaxseed, are high in fiber, essential for digestion. Fiber promotes regularity and supports colon health. Lignans also act as prebiotics, feeding beneficial gut bacteria and enhancing the gut microbiome.
Sources and Considerations
Lignan concentration varies in foods. Top sources include:
- Flaxseeds: Richest source; consume ground for better absorption.
- Sesame Seeds: Excellent source, comparable to flaxseed.
- Other sources: Whole grains (rye, barley), cruciferous vegetables (broccoli), soybeans, legumes, berries, and some fruits contain smaller amounts.
Note that flaxseed oil has few lignans. While dietary lignans are generally safe, those with hormone-sensitive conditions, or who are pregnant or breastfeeding, should consult a healthcare professional before taking supplements.
Lignans vs. Other Phytoestrogens
| Feature | Lignans | Isoflavones (e.g., in Soy) |
|---|---|---|
| Primary Source | Flaxseeds, sesame seeds, whole grains | Soybeans and soy products (tofu, tempeh) |
| Chemical Type | Polyphenols, specifically diphenolic compounds | Flavonoids, specifically isoflavonoids |
| Effect on Body | Converted by gut bacteria into enterolignans (enterodiol, enterolactone) which have antioxidant and hormone-modulating effects | Metabolized into active forms that also bind to estrogen receptors, but often with higher estrogenic potency in some contexts |
| Key Functions | Antioxidant, anti-inflammatory, hormone-balancing, cardiovascular support | May influence hormone balance, bone density, and heart health |
| Abundance | Particularly high concentration in flaxseed | High concentrations in soy products and legumes |
Conclusion
Lignans are potent plant polyphenols with numerous health benefits. Converted by gut bacteria into active enterolignans, they function as powerful antioxidants, help balance hormones, protect cardiovascular health, and may lower the risk of certain cancers. Including lignan-rich foods like ground flaxseed and sesame seeds in the diet can support overall health. Ongoing research continues to reveal what do lignans do for the body, highlighting their potential as a dietary tool for health promotion.
Visit the National Institutes of Health (NIH) website for more scientific information on lignans.
