Flaxseed (flax) contains high levels of secoisolariciresinol diglucoside (SDG). SDG belongs to a class of phytoestrogens (i.e., plant compounds) called lignans, which have been shown to reduce blood levels of specific estrogens associated with the development of breast cancer. Lignans can block the production of estrogen in the body and may be able to inhibit the growth of breast cancer cells.
For postmenopausal women with a high risk of breast cancer, flax may have preventative benefits. In a recent study, postmenopausal women who consumed 5 or 10 grams of ground flaxseed over a 7-week period showed significant reductions in blood concentrations of the most potent estrogen, estradiol, and its breakdown product, estrone.
Preliminary studies indicated that flax may not support the same preventative benefits in premenopausal women. A recent study of 116 premenopausal women found that the women who ate 25 grams of ground flax daily for one year showed no reductions in estradiol or breast density.
Useful forms of flaxseed to add to your diet are the flaxseed itself, flaxseed oil, or foods made with flaxseed. Flaxseed (whole or ground) has a very pleasant, nutty flavor. You can sprinkle flaxseed on salads, cooked vegetables, or cereals. Also, ready-made flaxseed breads, muffins, and breakfast bars are available at health-food stores.
Flaxseed oil, which is extracted from flaxseed, also can be purchased at your local health-food store. Usually, flaxseed oil is kept in the refrigerated section with other perishable supplements and foods. You can store a bottle of flaxseed oil in you refrigerator for up to 3 months. One or two capfuls of flaxseed oil on top of a salad or mixed into a smoothie is a great way to take this important nutrient. Flaxseed oil, however, cannot be used for cooking or sauteing foods.
On the other hand, commercial flaxseed supplements, which are not the same as whole or ground flaxseed and are not the same as flaxseed oil, have little or no benefit.
As with any supplements, before adding flaxseed or flaxseed oil to your diet, be sure to first consult with your integrative healthcare professional.