Objective: Low levels of selenium have been associated with a higher risk of cardiovascular diseases and cancer in humans. Since 1984, selenium supplementation through fertilizers has been employed in Finland to increase the very low concentration of selenium in the nation's food supply. As a result, the selenium concentration of Finnish foods became one of the highest in Europe. A decade after selenium supplementation began, the association between toenail selenium and the risk of breast cancer was examined.
Design: Case-control study.
Setting: Eastern Finland.
Subjects: 289 pre- and postmenopausal breast cancer cases and 433 community controls. The diagnosis was unknown at the time the toenail samples were collected.
Results: The mean toenail selenium concentration was 0.80 mg/kg in premenopausal cases and 0.84 mg/kg in premenopausal controls: and 0. 77 mg/kg in postmenopausal cases and 0.80 mg/kg in postmenopausal controls. The odds ratio (OR) comparing the highest with the lowest quintiles of toenail selenium concentration was 1.1 (95% CI 0.4-3.2) in premenopausal women and 0.7 (95% CI 0.3-1.5) in postmenopausal women. The intake of retinol, beta-carotene, vitamin E and vitamin C did not change the association between toenail selenium and breast cancer.
Conclusions: A decade after selenium supplementation, selenium seems not to be an important factor in the etiology of breast cancer, neither in premenopausal nor postmenopausal women.
Sponsorship: This work was supported by the EVO funds from the Kuopio University Hospital and by research grants from the Academy of Finland, Yrjö Jahnsson Foundation and Juho Vainio Foundation. European Journal of Clinical Nutrition (2000) 54, 98-103