A recent study found that dim lighting reduces the amount of melatonin produced.

This is bad for cancer sufferers as Dr Steven M Hill said: “[Melatonin has] profound inhibitory effects on various cancers, particularly breast cancer.” The decline in melatonin could lower the effects of Tamoxifen – a breast cancer drug.

Dr Steven M Hill, professor of structural and cellular biology and the Edmond Lily Safra chair for breast cancer research at Tulane University School of Medicine in New Orleans, and a team of scientists conducted an experiment on rats. The experiment involved some rats living with 12 hours of daylight and 12 hours of darkness and other rats exposed to 12 hours of daylight and 12 hours of dim lighting. The rats in the light and dark conditions had an increase in melatonin as the night got darker but decreased as the light got brighter. The rats in the light and dim conditions had consistently low melatonin levels throughout. The results showed how vital melatonin is. The rats with less melatonin (dim lighting) had their tumours grow 2.6 times faster than the rats with higher rates of melatonin. However, when rats in the dim lighting were given a melatonin supplement their tumours shrank.

Dr Hill said that the amount of lighting that could decrease the effectiveness of the drug could be as weak as a street light shining through a bedroom window. There are plans to conduct more studies to answer exactly how much light is harmful.

Our data, although they were generated in rats, have potential implications for the large number of patients with breast cancer who are being treated with tamoxifen, because they suggest that night-time exposure to light, even dim light, could cause their tumours to become resistant to the drug by suppressing melatonin production.

As far as giving out melatonin supplements with the tamoxifen, enough research has not been done.

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.

During the night, if you sleep in a brightly lit room, your melatonin levels may be inhibited; however, if you are in the dark but cannot sleep, your melatonin levels will rise normally,”

Dr Hill, says that sleep is not a factor, it is the light that makes the difference.

This Study was published in Cancer Research: a journal of the American Association for Cancer Research.

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