Lignans

Lignans are plant chemicals we call phytoestrogens because of their weak estrogen-like characteristics. They occur naturally in many plants, including wheat, barley, oats, legumes, garlic, asparagus, broccoli, and carrots. Flaxseed is by far the richest natural source of lignans, containing about 10 to 20 times the amount of their nearest rival.

Flax is a particularly rich source of the lignan secoisolariciresinol diglycoside (SDG), which has anticarcinogenic and strong antioxidant properties. Its metabolites appear to selectively bind to sex hormone-binding globulin (SHBG) in the body, thus blocking estrogen and testosterone uptake an important characteristic given the presence of SBGH in many cancer cells, including breast cancer. As phytoestrogens, lignans appear to have a regulating effect on our immune system and hormone production (particularly in women).

What Science Tells Us

Plant lignans appear to work synergistically with alpha linoleic acid (ALA), also found in flax, to block the formation of platelet-activating factor, a compound that regulates inflammation, platelet aggregation, and some immune system responses. The body converts the phenolic compounds found in plant lignans into human lignans, principally enterodiol and enterolactone, through bacterial reaction in the human colon.

Research on lignans indicates that they have great potential in preventing and/or treating a number of conditions, including hormone-sensitive cancers such as breast, prostate, and colon cancer (the site of conversion of SDG to human lignans). Research also shows they are effective in inflammatory disorders such as coronary heart disease, arthritis, and lupus erythematosus. They promote optimal immune system function, as well as hormone balance in women. Diabetics may also find benefit in their use.

Fresh is Best

Flax is the most concentrated and practical dietary source of plant lignans. In order to use flaxseed effectively it should be ground or milled, preferably just before use. Once the seed is broken it should be refrigerated, as it is prone to going rancid. Lignan-enriched flax oil is also available as either liquid or capsules, and should be refrigerated at all times. Ground flaxseed contains approximately 50 to 150 mg of plant lignans per tablespoon (15 mL) and lignan-enriched flax oils may contain upwards of 14 mg per tablespoon.

There is no established dietary recommendation regarding lignans although the Flax Council of Canada suggests that 1 Tbsp (15 mL) of flaxseed or ½ tsp (2 mL) of flax oil daily contributes to better health. Whether to use flax oil or flaxseed is partly a matter of preference and convenience the oil has a higher essential fatty acid content with its own attendant health benefits whereas the ground seed is also a source of dietary fibre.

Find Out More

For more information on lignans and flaxseed in general, contact the Flax Council of Canada (telephone 204-982-2115 or email flax@flaxcouncil.ca). The Council publishes an excellent research summary entitled "flax - A Health and Nutrition Primer," available on their website at flaxcouncil.ca.

The best place to purchase flax products is at your local health food store or nutrition centre. As a rule these retailers are more careful about the storage requirements for these products and know more about them, too.

Lignans found in flaxseed and other plant sources are essential additions to our diet as a preventive against cancers, heart disease, and arthritis.