Relationship between selenium and breast cancer: a case-control study in the Klang Valley.

INTRODUCTION: The purpose of this study was to assess the relationship between selenium status and intake among breast cancer patients from the Klang Valley.
METHODS: 64 cases and 127 controls were matched for age (range 30-65 years) and ethnicity, with an 80 percent study power. Subjects were interviewed to obtain information on their habitual dietary intakes, demographic data and medical history. Selenium status was determined from toenail and hair analysis using an inductively coupled plasma mass spectrometer.
RESULTS: The nutrient analysis showed that total energy and protein intake was significantly higher among controls (1,403 +/- 367 kcal/day, 75.6 +/- 33.2 g/day) as compared to cases (1,273 +/- 295 kcal/day, 60.9 +/- 19.1 g/day) (p-value is less than 0.05). The selenium intake among cases (78.47 +/- 25.34 ug/day) was significantly lower than the controls (89.34 +/- 36.85 ug/day) (p-value is less than 0.05). Breast cancer risk decreased with the increasing quartiles of selenium intake, with odds ratios (95 percent confidence interval) of 2.95 (1.22-7.12), 2.17 (1.13-4.19) and 1.71 (0.84-3.52), respectively. However, the association diminished after adjustment for confounding factors. Selenium in hair did not differ among cases and controls, but selenium status in the nails of controls was significantly higher as compared to cases (p-value is less than 0.05). Breast cancer risk decreased with the increasing quartiles of toenail selenium status as measured in the toenail and hair.
CONCLUSION: Selenium intake and status was associated with breast cancer risk. Thus, it is essential for Malaysian women to achieve a good selenium status by consuming good food sources of selenium as a chemopreventive agent.