Want Your Tamoxifen to Work? Turn Off the Lights!

A recent study has revealed that exposure to dim lighting during the nighttime, as opposed to no lighting at all, may reduce the positive effects of prominent breast cancer drug tamoxifen. According to BBC, the results indicate that reduced lighting slows the body‘s production of melatonin, thereby limiting the effectiveness of the medication. Melatonin, a hormone secreted by the pineal gland, has significant inhibitory effects on various cancers, particularly breast cancer.

The study, conducted by Dr. Steven M. Hill at Tulane University in New Orleans, featured two sets of rats with tumors. One set experienced 12 hours of daylight and 12 hours of darkness, while the other experienced 12 hours of daylight and 12 hours of dim lighting.

The rats that experienced the contrast of light and total darkness had increased melatonin levels in darkness and decreased levels in light. On the other hand, the rats that were in dim lighting at night had low melatonin levels consistently. According to the New York Daily News, the tumors of rats from the group with dim lighting experienced an increased growth rate, 2.6 times faster than in the other rats, as they resisted the effects of the drug.

Photo: Adobe Stock/sharpshutter22
Photo: Adobe Stock/sharpshutter22

“Melatonin is produced by our bodies at a very specific time of day, exclusively during darkness at night, and taking melatonin supplements at the wrong time of day would potentially disrupt the circadian system, particularly the natural melatonin cycle, which may, in itself, paradoxically impair breast cancer responsiveness to tamoxifen​,” Hill says.

More studies need to be done, but the findings may indicate bedroom lighting as a key to those taking tamoxifen.

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