Lignans are a group of chemical compounds found in plant-based foods including flaxseeds, sesame and pumpkin seeds, and rye. When these foods are digested, intestinal bacteria activates the lignans. Lignans are considered phytoestrogens, states the University of Maryland Medical Center, and may act as weak or antiestrogens in your body. Research is being conducted in regard to its anti-cancer, anti-inflammatory properties, as well as its possible benefit of reducing the risk of heart disease and lowering cholesterol levels.

Cancer
The richest source of lignans comes from crushed or macerated flaxseeds. A study published in 2010 in the "British Journal of Nutrition" tested the lignan from flaxseeds in regard to cancer. They found that flax lignans might lower your cancer risk by preventing pre-cancerous cellular changes, as well as slow down the progression and movement of cancer cells. The American Cancer Society reports that lignans may help to reduce the growth of hormone-related cancers including prostate, breast and ovarian cancer, though more human research is needed.
In 2006, the "American Journal of Clinical Nutrition" published research stating that because of its antioxidant effects, lignans may help reduce the risk of cardiovascular disease. According to the Linus Pauling Institute at Oregon State University, it is not clear whether it is the lignans providing the reduced risk of heart disease, or the combination of nutrients and phytochemicals, which are found in foods like flaxseeds. Overall, a diet that includes seeds, whole grains and vegetables will lower your risk of heart disease and provide your body with lignans.
In 2008, a study published in "British Journal of Nutrition" showed promising results in regard to cholesterol and glucose levels. An 8-week study was conducted on 55 patients, which resulted in a significant initial decrease in total cholesterol levels. Taking lignans on a regular basis does appear to lower LDL cholesterol levels; however, more research is still needed.