Dietary phytoestrogen intake and mammographic density -- results of a pilot study

The influence of dietary phytoestrogens provided by Western diets on mammographic density is not well established. Soy and soy products as source of isoflavones were found to be inversely associated with high mammographic density, a marker for breast cancer risk. Another class of phytoestrogens, the lignans, which are more frequent in Western diets, are rarely investigated. Within the European Prospective Investigation into Cancer and Nutrition cohort in Heidelberg (EPIC-Heidelberg) we explored the feasibility of mammogram collection and measurement of mammographic density in order to investigate the association between dietary phytoestrogen intake and breast density patterns. Wolfe classification was used to summarize mammographic density. Dietary habits were assessed by means of a validated food frequency questionnaire. - Out of the 505 randomly selected women, 317 (63%) returned the questionnaire and 310 (61.4%) women provided informed consent to collect mammograms. Dietary intake of seven women with dense patterns (DY) was compared with 47 women without dense patterns. A high dietary intake of fibre (p-value = 0.008) and secoisolariciresinol (p-value = 0.043) is inversely associated with non-dense breast patterns. This is also observed for a high dietary intake of soy-products (p-value = 0.004) and, in tendency, genistein (p-value = 0.069). After adjustment for energy intake and age the groups of dense and non-dense mammographic patterns were different regarding the intake of carbohydrate (p = 0.032), soy-products (p = 0.020), fibre (p = 0.046), and secoisolariciresinol (p = 0.027). - Our results suggest an inverse association between dietary lignan intake and breast density, similar to the findings for isoflavones. To our knowledge this is the first report on this association, but due to the risk of chance finding, this has to be confirmed in a study with sufficient statistical power.