Plasma enterolactone and risk of colorectal cancer
Nina Føns Johnsen, Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
Investigations on risk factors for colorectal cancer have shown that a diet high in fat and low in fiber and vegetables is associated with increased risk. Vegetables and whole grains contribute to the intake of fibre and contain the lignan phytoestrogens. Plant lignans are compounds present predominantly in the fibre components of whole grains cereals, nut and seeds, vegetables, berries, but they have also been found in beverages such as coffee, tea and wine. Plant lignans are converted to the mammalian lignan, enterolactone, by the action of bacteria in the large intestine. A high intake of fat or use of antibiotics has been shown to inhibit this process.
Enterolactone is of interest due to a possible protective effect against breast cancer. Colorectal cancer may, like breast cancer, be a hormone-dependent cancer. Studies indicate that colorectal cancer is associated with a potential disorder of the estrogen-mediated pathways as users of hormone replacement therapy have lower risk of developing cancer in the colon and rectum, and moreover, estrogen receptors (a and ß) are present in the colon, but colorectal cancer is associated with a loss of the ß-type estrogen receptors, which normally controls the proliferative estrogen receptor a. In vitro and animal studies have shown that enterolactone possesses several steroid modulating and anti-proliferative properties, giving enterolactone the potential to protect against hormone-dependent cancers.
The aim of this study is to investigate the association between the plasma concentration of the phytoestrogen, enterolactone, and the incidence of cancer in the colon and rectum in a Danish prospective cohort study including 57,053 men and women. Baseline information includes data on diet and lifestyle from a self-administered questionnaire and blood samples which have been analyzed for enterolactone by time-resolved fluoroimmunoassay.
The traditional Scandinavian diet is rich in whole grains and especially rye bread, and results from this prospective study will provide valuable information about possible cancer preventive effects of phytoestrogens in the Nordic diet. In Denmark the intake of rye bread is declining in favour of the Italian white bread types, and if enterolactone is associated with lower risk of colorectal cancer, people should be advised to increase their intake of lignan-rich foods like rye bread and other whole grain foods.