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Breast Cancer Drug May Work Best in the Dark

New research suggests that exposure to light at night may undermine treatment with Tamoxifen, a drug often prescribed to breast cancer patients after surgery to prevent recurrence of the disease. This finding came from a study with rats that demonstrated inadequate amounts of melatonin render breast cancer tumors resistant to the effects of Tamoxifen. The researchers noted that the same mechanism might be of concern in humans, and pointed out that even dim light in the bedroom can suppress production of melatonin, a hormone that influences sleep-wake cycles. The investigators didn’t pinpoint how much light may cause this effect, but suggested it could be as little as the amount that comes in a bedroom window from a street light. When they gave the rats a melatonin supplement, the animals’ tumors no longer resisted the effects of Tamoxifen. The researchers didn’t recommend that breast cancer patients take melatonin supplements, however, and raised the issue that taking the supplements at the wrong time of day could disrupt the natural cycle of melatonin production. It is darkness, not sleep, that triggers melatonin production. Sleeping in a dark room allows melatonin levels to rise normally, whether or not you’re taking Tamoxifen.

Steven M. Hill et al, “Circadian and Melatonin Disruption by Exposure to Light at Night Drives Intrinsic Resistance to Tamoxifen Therapy in Breast Cancer,” Cancer Research, doi:10.1158/0008-5472.CAN-13-3156

Melatonin for More Sleep and Better Bones

Melatonin might not be the entire solution for women prone to thinning bones, but at least the hormone seems to have strengthened the skeletons of elderly rats, suggesting that it might be an approach to osteoporosis prevention in humans. Researchers at the McGill School of Dentistry found that giving 22-month-old rats (about age 60 in human years) melatonin for 10 weeks (the equivalent of six human years) led to an increase in bone volume, bone density and bone flexibility compared to rats of the same age that didn’t receive melatonin. The rationale behind this study is that osteoclasts, the cells that break down bone, are active at night, while bone-building osteoblasts are active during the day. Since humans tend to sleep less well as they get older, osteoclasts become more active in the time they operate, speeding bone breakdown. Melatonin, known to regulate circadian rhythm, seems to have boosted bone building in the rats, but the researchers still need to determine if the supplement prevented bone breakdown or actually promoted repairs of damage bones. More research and clinical trials are now needed to find out exactly how melatonin influences skeletal health. Stay tuned.

Faleh Tamimi et al, “Melatonin dietary supplement as an anti-aging therapy for age-related bone loss,” Rejuvenation Research, doi:10.1089/rej.2013.1542.