Chemoprevention of Breast and Prostate Cancers in Shift Workers by Dietary Methylselenocysteine: Effects on Circadian Rhythm and Estrogen Receptor-B Cycling

All living cells have a circadian (daily) rhythm which controls a variety of bodily functions that change throughout the day, including body temperature, sleep, hunger, activity, hormone levels, etc. The circadian rhythm of the body is controlled by the amount of light that enters our eyes, so on our planet the length of the rhythm is 24 hours long. It is therefore reasonable to suspect that upsetting the timing of the rhythm would lead to changes in body function (as commonly experienced in "jet lag") and that prolonged changes might even lead to alterations in bodily functions and contribute to disease. This suggests that people whose service to the community that requires that they often work at night (nurses, doctors, police, hospital staff, firefighters, airline crews, factory workers, etc), might be at elevated risk of developing diseases. Studies have shown that women who do shift work have an elevated risk of breast cancer, probably as a result of altered hormone levels and cycling. Other studies have shown that vitamin supplementation with a naturally occurring dietary amino acid called organic selenium (i.e., methylselenocysteine) can restore this disrupted rhythm and possibly decrease this disease risk. Thus, the purpose of this study is to investigate whether taking daily selenium (i.e., methylselenocysteine) will restore the disrupted circadian rhythm in shift workers.