Lignans are naturally occurring compounds found in various plants. These plant-derived components are present in many common foods, contributing to their nutritional value. Research continues to explore how these compounds interact with the human body and their broader implications for health.
Defining Lignans
Lignans are a category of polyphenols found in plants. They are also classified as phytoestrogens, plant-derived compounds that can exert weak estrogen-like effects in the body. In plants, lignans act as secondary metabolites, contributing to defense mechanisms.
These compounds are formed through the oxidative coupling of monolignols. Secoisolariciresinol diglucoside (SDG), matairesinol, and pinoresinol are among the most studied lignans due to their relevance in human diets. SDG is notable as a precursor extensively metabolized in the human body.
Dietary Sources of Lignans
Lignans are widely distributed across various plant-based foods, though their concentrations vary. Flaxseeds are the richest dietary source, containing high levels of secoisolariciresinol diglucoside. Sesame seeds are also a significant source.
Beyond these seeds, lignans are found in whole grains such as rye, oats, and barley. Many fruits, including berries and apricots, contribute to dietary lignan intake. Various vegetables like broccoli and cabbage also contain these compounds. The specific content of lignans in foods can differ based on factors like geographic location, climate, and plant maturity.
Transformation and Action in the Body
When consumed, dietary lignans undergo transformation within the human digestive system. This process relies heavily on the activity of gut microbiota, the beneficial bacteria residing in the intestines. These microorganisms convert the ingested plant lignans into biologically active forms known as enterolignans.
The two primary enterolignans formed are enterodiol and enterolactone. After their conversion, these enterolignans are absorbed into the bloodstream and circulate throughout the body. Once absorbed, enterolignans exert their influence through two main mechanisms. They act as weak phytoestrogens, binding to estrogen receptors in cells and mimicking some effects of natural estrogens, though with less potency. Additionally, enterolignans possess antioxidant properties, helping to scavenge free radicals, unstable molecules that can cause cellular damage.
Lignans and Their Impact on Health
The actions of enterolignans in the body contribute to several physiological impacts, stemming from their phytoestrogenic and antioxidant properties. Their influence on hormonal balance is an area of ongoing study. Lignans may play a role in managing symptoms associated with menopause by interacting with estrogen receptors. They are also being investigated for their potential contributions to prostate health.
Lignans have shown promise in supporting cardiovascular health. Research indicates a positive effect on lipid profiles in individuals with dyslipidemia, suggesting a potential role in managing cholesterol levels. Some studies have also explored their relationship with blood pressure regulation, though more research is needed. The antioxidant capacity of enterolignans contributes to cellular protection. By neutralizing free radicals, they help safeguard cells from oxidative stress, a process linked to various chronic conditions. Research on the full spectrum of lignans’ health benefits is continuously evolving.