Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk.
Consumption of flaxseed, a rich source of lignans, is associated with reduced breast cancer risk.
Year: 2013
Authors: Lowcock, E.C. Cotterchio, M. Boucher, B.A.
Publication Name: Cancer Causes Control
Publication Details: DOI 10.1007/s10552-013-0155-7
Abstract:
Purpose To investigate the association between intake of flaxseed, the richest source of dietary lignans (a class of phytoestrogens), and breast cancer risk. Methods A food frequency questionnaire was used to measure the consumption of flaxseed and flax bread by 2,999 women with breast cancer and 3,370 healthy control women who participated in the Ontario Women’s Diet and Health Study (2002 to 2003). Logistic regression was used to investigate associations between consumption of flaxseed and flax bread and breast cancer risk. Confounding by established and suspected breast cancer risk factors, as well as dietary factors, was assessed. Results Flaxseed or flax bread was consumed at least weekly by 21 % of control women. None of the 19 variables assessed were identified as confounders of the associations between flaxseed or flax bread and breast cancer risk. Consumption of flaxseed was associated with a significant reduction in breast cancer risk, as was consumption of flax bread. Conclusions This Canadian study is, to our knowledge, the first to report on the association between flaxseed alone and breast cancer risk and has found that flaxseed intake is associated with a reduction in breast cancer risk. As dietary intake of flaxseed is modifiable, this finding may be of public health importance with respect to breast cancer prevention. (Authors abstract)
Lignans are found in many plant foods, but flaxseed is the richest source, containing more than 300 mg per 100 g serving. Despite its contribution to dietary lignin intake, flaxseed has not been measured in most studies assessing lignans and breast cancer risk. The Ontario Women’s Diet and Health Study is a population-based case–control study conducted to investigate associations between dietary phytoestrogens and breast cancer risk. Intakes of phytoestrogen-containing foods, including flaxseed and flax bread, were measured, and in 2008, the authors reported that total lignan intake may be associated with reduced risk of breast cancer. Among controls, flaxseed was the major lignan contributor; similarly, a Swedish study reported that flaxseed contributed substantially to total lignan intake. It was therefore of interest to examine the association between flaxseed consumption specifically and breast cancer risk. These flaxseed findings are consistent with recent meta analyses suggesting that dietary lignin intake may be associated with a modest reduction in breast cancer risk, particularly in postmenopausal women and emphasize the need to capture flaxseed in dietary assessments of lignan consumption. In this study, 21 % of controls reported consuming flaxseed or flax bread at least weekly. As one teaspoon contains more than 13 mg of lignans, only a small daily serving of flaxseed is required to attain the level of lignin intake previously shown to be associated with a reduction in breast cancer risk (e.g. 5.4 mg/day). As it appears that most women do not consume flaxseed and that small amounts may be associated with reduced breast cancer risk, interventions to increase the prevalence of flaxseed consumption might be considered. Intervention studies have been conducted to investigate the impact of flaxseed on markers of cardiovascular disease and diabetes management, with favorable results. (Editors comments)
