Lignans are phytoestrogens with estrogenic or anti-estrogenic activity. Lignans may also have antioxidant activity. Plant lignan compounds are converted in the intestine to a form of lignans (enterolignans) the human body can assimilate. Some studies have reported a positive association between high levels of lignans in the body with reduced risks of  cancers (prostate, ovarian, and breast cancers), osteoporosis, and cardiovascular disease. On the other hand, some studies also reported no association between intake of high lignan diet and risk of breast cancer.

Lignans comprise a variety of compounds, both in food sources (secoisolariciresinol, matairesinol) and in the human body (enterodiol, enterolactone). Some studies reported that the health effect of the lignans varied depending on the particular lignan type in the food, fore example secoisolariciresinol vs. matairesinol.

Dietary lignan compounds are found in many food sources. Among all, flax seed is high in lignan content, perhaps the richest source of lignans. Some of the same lignan food sources are also good sources of dietary fiber, protein, antioxidants and other nutritional elements. In the following table is a list of food stuffs and beverages and their total lignan content. The estimate of lignan content in the foods, gathered in the Netherlands, was reported by Dutch researchers.

Table 1. Lignan content (μg/100 g fresh edible weight) of solid foods.