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Dietary lignans improve breast cancer survival

Jacob Schor, ND, FABNO

July 20, 2010

Even a slight increase in dietary lignan may change survival statistics.

A paper published this month may change the way we think about diet and breast cancer for years to come.  Susan McCann from Roswell Research Center near Buffalo, New York teamed up with Lillian Thompson of the University of Toronto and mined data already collected on diet and breast cancer.

The data came from 1,122 women diagnosed with breast cancer between 1996 and 2001 that was collected as part of a study looking at lifetime alcohol consumption and breast cancer (WEB Study).  Dr. Thompson recently published a comprehensive analysis that lists the lignan content of foods common in the Canadian diet.

With the diet information from the WEB Study and the ability to analyze lignan content and knowledge of the ‘vital status’ of the study participants updated in 2006, there was adequate data; the association between dietary lignan intake and survival was analyzed. Hazard ratios (HR) for dietary lignan intake with all cause, and breast cancer mortality were calculated.

Postmenopausal women followed in the study who consumed the most lignan had a significantly lower risk of dying from any cause and especially from breast cancer when compared to women who ate only small amounts of lignan containing foods. 

The women were consuming the most lignan in their diets at the start of the study had about half the risk of dying as those who ate little lignan. 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 same women were far less likely to die of breast cancer.   They 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.

This is the first paper we know of that examines the association of lignan intake prior to breast cancer diagnosis and the risk of dying.  This is relevant.  Dying after all is the bottom line when we are talking about cancer isn’t it? These findings suggest that postmenopausal women should be making an active effort to increase dietary lignan intake.

Ever since the data from the from the Women's Healthy Eating and Living (WHEL) trial was published that suggest that high fruit and vegetable and low fat diets have relatively little effect on breast cancer prognosis, those of us in clinical practice have sought to define what a ‘good’ diet should be for patients at risk for or diagnosed with breast cancer.   

Encouraging high lignan intake is easier said than done as few patients will understand what  ‘lignans’ are and what foods contain contain a substantial amount.  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, and equal weight of kale contains several thousand mcg of lignans.  Flaxseed contain over 300,000 mcg/100 gram and sesame seeds almost 40,000 mcg.

In the McCann and Thompson study, average lignan intake averaged only 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 easy to accomplish, for example 0.1 grams of flax seed provide close to this dose of lignan.  A chart of lignan content of foods is posted at: http://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.  In other words, this may not work as effectively in real life.  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.

 

Related articles:

Flax seed oil and Herceptin: http://denvernaturopathic.com/flaxoilandherceptin.htm

Flax seeds and Breast Cancer: http://denvernaturopathic.com/news/flaxseeds.html

Flax seed muffin recipe:  http://denvernaturopathic.com/news/flaxseeds.html

References:

McCann SE, Thompson LU, Nie J, Dorn J, Trevisan M, Shields PG, 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 Jul;122(1):229-35.

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 Feb;21(1):86-91.

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