Dietary Lignans Improve Breast Cancer Survival

Examines the association of lignan intakes prior to breast cancer diagnosis and risk of dying.

By Jacob Schor, ND, FABNO

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Reference

McCann SE, Thompson LU, Nie J, et al. Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study. Breast Cancer Res Treat. 2010;122(1):229-235.

Design

Statistical mining of data collected on dietary habits of women with breast cancer. Diet in the 12–24 months before diagnosis was assessed with an extensive food frequency questionnaire, and confounders assessed from an epidemiologic interview and abstracted clinical data. Lignan intake was calculated using published food composition data.
Participants: 1,122 women, aged 35–79 years, diagnosed with breast cancer between 1996 and 2001. Data were collected as part of a study looking at lifetime alcohol consumption and breast cancer (WEB Study).

Study Methodology

The association between dietary lignan intake and survival was analyzed. Vital Status was tracked until the end of 2006. Extensive food questionnaires were used to track diet for 1–2 years before initial diagnosis. Lignan intake was calculated using current food composition tables. Hazard ratios (HR) for dietary lignan intake with all-cause and breast cancer mortality were calculated.

Outcome Measure

Vital status (living or deceased)

Key Findings

Postmenopausal women who consumed the most lignans had a significantly lower risk of dying from any cause and especially from breast cancer than women who ate only small amounts of lignan-containing foods. When upper versus lower quartiles of lignan intake were compared, there was a 51% (HR 0.49, 95% CI: 0.26–0.91) reduction of all-cause mortality in those consuming the higher lignan levels. These women had a 71% decreased risk of dying of breast cancer (HR 0.29, 95% CI: 0.11–0.76). High intakes of dried beans (HR 0.61, 95% CI: 0.36–1.03) may have also lowered risk of overall mortality and breast cancer mortality (HR 0.53, 95% CI: 0.24–1.14), though these numbers did not reach statistical significance.

Practice Implications

This is the first paper to examine the association of lignan intakes prior to breast cancer diagnosis and risk of dying. These findings suggest that we should actively promote consumption of lignan-containing foods, particularly in postmenopausal women.

Still, if incorporating a few specific high-lignan foods into to the diet can reduce breast cancer mortality even a fraction of the amount seen in these data, it is certainly worth trying.

Ever since the data from the from the Women’s Healthy Eating and Living (WHEL) trial was published suggesting that diets high in fruits and vegetables and low in fat have little effect on breast cancer prognosis, researchers and clinicians have sought to define what a “good” diet should be for patients at risk for or diagnosed with breast cancer.1 Encouraging high lignan intake is easier said than done, as few patients will understand what a lignan is and which foods contain them. For the women enrolled in this study, the main food sources of lignans were dark bread, peaches, coffee, broccoli, and winter squash. Other foods are far better sources. While coffee may contain up to 30 mcg/100 ml, 100 grams of kale contains several thousand mcg of lignans. Flaxseeds contain over 300,000 mcg/100 grams and sesame seeds contain almost 40,000 mcg/100 grams.2

In McCann’s study, average lignan intake was 244 mcg/day. In the postmenopausal women, consuming <155 mcg/day yielded a HR for overall and breast cancer mortality of 1.00. As consumption levels increased HR dropped; the lowest risk of dying was seen in women consuming >318 mcg per day. Reaching these levels should be relatively easy to accomplish. Practitioners and patients may find a useful chart of lignan content of foods posted at: www.dietaryfiberfood.com/lignan.php

This study was not a clinical trial; perhaps that is why these results seem almost too good to be true. Still, if incorporating a few specific high-lignan foods into to the diet can reduce breast cancer mortality even a fraction of the amount seen in these data, it is certainly worth trying.

For more research involving integrative oncology, click here.

About the Author

Jacob Schor ND, FABNO, is a graduate of National College of Naturopathic Medicine, Portland, Oregon, and now practices in Denver, Colorado. He served as president to the Colorado Association of Naturopathic Physicians and is on the board of directors of the Oncology Association of Naturopathic Physicians. He is recognized as a fellow by the American Board of Naturopathic Oncology. He serves on the editorial board for the International Journal of Naturopathic Medicine, Naturopathic Doctor News and Review (NDNR), and Integrative Medicine: A Clinician's Journal. In 2008, he was awarded the Vis Award by the American Association of Naturopathic Physicians. His writing appears regularly in NDNR, the Townsend Letter, and Natural Medicine Journal, where he is the Abstracts & Commentary editor.

References

1. Pierce JP. Diet and breast cancer prognosis: making sense of the Women’s Healthy Eating and Living and Women’s Intervention Nutrition Study trials. Curr Opin Obstet Gynecol. 2009;21(1):86-91.

2. Milder IJ, Arts, IW, Van de Putte B., Venema DP, Hollman, PH. Lignan contents of Dutch plant foods: a database including lariciresinol, pinoresinol, secoisolariciresinol, and matairesinol. Br J Nutr. 2005;93:393-402.