New research conducted in the United States at the National Cancer Institute and National Institute of Environmental Health Sciences reveals a startling finding: Exposure to light during the hours of sleep appears to aggressively promote breast cancer.
This effect is achieved due to light's ability to shut off production of melatonin, a hormone produced by the pineal gland. This hormone, which is naturally produced by the body during the hours of darkness, is known to be a strong immune system booster. Its presence also impedes the growth of cancer tumors by as much as 80 percent, according to research findings.
To determine the effect of light-moderated hormones on cancer tumors, scientists grafted human breast cancer tumors onto rats and infused the tumors with blood drawn from adult women. Blood taken from women exposed to artificial light sources at night actually accelerated the growth of the breast cancer tumors, but blood from women who slept in the dark was found to halt the growth of the tumors by 80 percent.
Lead researcher Dr. David Blask characterized it as, "...the first proof that light is indeed a risk factor for cancer." The research may also help explain why night shift workers (such as nurses and flight attendants) are up to 60 percent more likely to be diagnosed with breast cancer.
"Breast tumors are awake during the day, and melatonin puts them to sleep at night," adds Dr. Blask.