Flaxseed, the “grain of the ancients,” is packed with omega-3 fatty acids (24%), dietary fiber (28%) and lignan phytoestrogens. It is also the focus of growing interest in the role that natural phytoestrogens may play in reducing certain cancer risks.

At present, evidence of such benefits from phyto-estrogens is circumstantial…“it is encouraging but not definitive,” says University of Toronto professor of nutrition, Lilian Thompson. Definitive conclusions will have to await additional human clinical data.

Hormone Therapy: Risks and Benefits

Breast cancer kills about 45,000 women every year, 70% of them post-menopause. For men, prostate cancer kills about 37,000 per year, 81% of which are over 65. These cancers appear to be associated with elevated levels of sex hormones—estrogen in women and testosterone in men. It is against this backdrop that the recent publication of a study linking elevated risks of breast cancer in women to post-menopausal hormone replacement therapy (HRT) has kindled interest in natural phytoestrogens, such as lignans from flaxseed.

Natural Phytoestrogens

Beginning in the early 1980s, nutritional and medical studies suggested that certain plant compounds exhibit weak sex hormone-mimicking behaviors. Epidemiological studies indicated that people with elevated levels of serum lignans exhibit lower occurrences of certain cancers and cardiovascular disease. A number of studies suggest that phytoestrogens mimic the action of estrogen hormones at cellular binding sites—essentially fooling the body that it is receiving “hormone therapy.”

Epidemiological studies do not prove cause and effect. Numerous animal studies, however, have done so: the consumption or applications of flaxseed lignans did reduce the incidence and/or spread of certain cancers and tumor growth. But, animals are not humans, Thompson is quick to note. Only more human clinical studies can establish this link beyond doubt. One of the issues that human studies will also need to untangle is which benefits derive from flaxseed's lignans or from flaxseed's other nutraceutical components, such as omega-3 oils and dietary fiber.

University of Minnesota nutrition professor Joanne Slavin recommends that consumers interested in consuming phytoestrogens use “whole foods sources of phytoestrogens rather than isolated compounds, since we don't have research studies to help with dose and safety issues.”