Epidemiological Studies on Breast Health

In a case-control study in eastern Finland (2001) to examine the association between serum enterolactone and risk of breast cancer in Finnish women analysis was made of a 194 breast cancer cases (68 pre-menopausal and 126 postmenopausal) who entered the study before diagnosis and 208 community-based controls. The study found an inverse association between serum enterolactone and risk of breast cancer both among pre-menopausal and post-menopausal women. In the study high enterolactone levels were associated with higher consumption of rye products and tea and higher intake of dietary fiber and vitamin E compared with those with low serum enterolactone values. The study concluded that serum enterolactone level was significantly inversely associated with risk of breast cancer1.

A further case-control study of phyto-oestrogens and breast cancer (1997) at the University Department of Surgery, Queen Elizabeth II Medical Centre in Perth (Western Australia) investigated the potentially anti-carcinogenic biological activity of phytoestrogens. One hundred and forty four (144) women with newly diagnosed early breast cancer were included in the study along with an equal number of controls randomly selected from the electoral roll after matching for age and area of residence. Patients were interviewed by means of questionnaires, and a 72 h urine collection and blood sample were taken before any treatment started. The urine samples were assayed for the isoflavonic phytoestrogens daidzein, genistein, and equol, and the lignans enterodiol, enterolactone, and matairesinol. The study found that after adjustment for age at menarche, parity, alcohol intake, and total fat intake that there was a substantial reduction in breast-cancer risk among women with a high intake (as measured by excretion) of phyto-oestrogens particularly the isoflavonic phyto-oestrogen equol and the lignan enterolactone2.

A United Kingdom population-based case-control study reporting in Cancer Causes Control (2004) investigated whether intake of phyto-oestrogens is associated with breast cancer risk. The study focused on South Asian women from the Indian subcontinent whose diet is rich in pulses and vegetables but poor in soy foods. A total of 240 South Asian breast cancer cases living in England and 477 age-matched population-based controls were recruited into the study. After adjustment for known breast cancer risk factors and total energy intake, the study found a dose-effect response in the odds of breast cancer risk within the second, third and highest quartiles of total lignan intake3.

The 2004 study conducted by Institute of Cancer Epidemiology (Copenhagen, Denmark) aimed at testing the hypothesis that enterolactone could be a protective agent against breast cancer due to estrogenic activity, found a tendency toward a lower risk for breast cancer with higher concentrations of enterolactone, which in this study appeared restricted almost entirely to ERalpha-negative breast cancer4.

In a study conducted by the Roswell Park Cancer Institute (USA) reporting on the potential of the mammalian lignans enterolactone and enterodiol to affect breast cancer breast cancer risk through modulation of endogenous estrogen metabolism or competitive inhibition with estrogen receptors conducted a case-control study of 1,122 women with primary, incident, histologically confirmed breast cancer and 2,036 control subjects matched according to cases age and county of residence identified that premenopausal women in the highest quartile of dietary lignan intake had reduced breast cancer risk (OR = 0.66; 95% CI = 0.44-0.98)5.