Current Research
According to a study published in 2011 in The Journal of Nutrition the phytoestrogen lignans are naturally occurring compounds with structural similarity to endogenous estrogens. Lignans are widely available in whole grains, seeds, nuts, legumes, fruit, and vegetables, with the highest concentration in flaxseed and bakery products containing flaxseed.
In human and experimental studies, high lignan intakes (from flaxseed) affect endocrine and growth factor pathways through a number of mechanisms, including modification of steroid hormone metabolism, modification of insulin-like growth factor and epidermal growth factor, and inhibition of aromatase and 17β-hydroxysteroid dehydrogenase. Lignans inhibit cell proliferation in both ER+ and ER− cell lines, reduce tumor growth and metastasis in a number of animal models, and work synergistically with Tamoxifen to reduce tumor growth.
Several, but not all, epidemiologic studies report reduced risks of breast cancer associated with higher exposure to dietary lignans, expressed as either dietary intakes or as plasma, serum, or urinary lignan concentrations. The protective effect of lignans may also be stronger in specific subgroups of women with breast cancer; lower risks have been reported to be limited to premenopausal women, women with specific CYP17 genotypes, and recently for ER− breast cancer (1).
Several studies have found that higher lignan intakes were associated with lower risks of breast cancer with more favorable prognostic characteristics, lower tumor biomarkers and inhibition of the growth and metastasis of human breast cancer (2).
All this said, Ruth Patterson, PhD who wrote an article entitled: Flaxseed and Breast Cancer: What Should We Tell Our Patients? in the Journal of Clinical Oncology states, "the prudent clinician should be wary of recommending high doses of any dietary compound solely on the basis of laboratory and observational epidemiologic studies". She based this opinion on the fact that in humans, lignans are metabolized by the gut microflora into enterolignans; enterolactone is the main metabolite. Therefore, enterolactone concentrations in serum, plasma, and urine have been used as biomarkers of dietary lignans. Studies indicate that women with higher levels of serum enterolactone have approximate 40% reduced risk of overall mortality and distant disease.
However positive this seems, there happen to be several variables that must be considered when using enterolactones as a secure indicator Patterson states: "Serum enterolactone concentrations are an imperfect measure of dietary intake because they reflect (in unknown proportions) dietary intake of lignans, other dietary and environmental exposures, and host characteristics" (3). Thus the take home message is baseline levels of enterolactones obtained from our daily diet may be supportive for breast cancer risk reduction but supplementing with higher quantities may or may not achieve this outcome.
Continued research is warranted to support supplemental flaxseed intake for breast cancer prevention and support. I recommend the use of flaxseed to be a part of a balanced diet using 1-2 tablespoon daily and only 1 tablespoon daily as an upper limit in ER+ patients.
Additional reading from leading cancer institutes:
Dana-Farber Cancer Institute
http://www.dana-farber.org/Health-Library/Phytoestrogen-s-Role-in-Estrogen-Positive-Breast-Cancer-Patients.aspx
Memorial Sloan-Kettering Cancer Center
American Institute for Cancer Research
References
1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3237232/
2. http://www.mskcc.org/cancer-care/herb/flaxseed
3. http://jco.ascopubs.org/content/29/28/3723
Image courtesy of: http://www.wikihow.com/Prepare-Flax-Seeds
No comments:
Post a Comment