Melatonin production is interrupted when we’re exposed to light in the wee hours of the morning.
Imagine an organ that regulates everything from sleep and mood to sex and food—an organ that Renee Descartes referred to as “the seat of the soul.” It’s called the pineal gland, and current research indicates that the possibilities for this hormone are endless.
Knowledge about the pineal gland's importance is not new. "Historically it's fascinating," says Dr. Lawrence Berk, MD, PhD, Radiation Oncologist at the Ohio Health and Grant Medical Center in Columbus, Ohio. "Renee Descartes, when he developed his theory of the mind, the body and the soul, said the soul is connected to the body by the pineal gland." According to Berk, the pineal gland is sometimes described as a third eye—the eye that enables the body to set its clock. In fact, the only organs in the body that are sensitive to light are the two "seeing eyes" and the eye in the pineal gland.
The pineal gland excretes melatonin, a brain hormone typically known for its ability to promote sleep and help people overcome jet lag. The specific functions of melatonin are not quite clear, but one of the things it is coordinated with is the body's clock, and that has far-reaching implications for disease management. Many diseases and conditions are affiliated with melatonin, including insomnia, fatigue, anxiety and, most recently, cancer.
It turns out melatonin has the ability to slow tumor growth and increase the survival time of cancer patients. A study conducted by Italian researchers found that melatonin alone can make tumors shrink. When given in conjunction with chemotherapy, melatonin reduced the toxicity of the medication.
Scientists studied 30 patients with glioblastoma, a very malignant form of brain cancer. The patients were given radiation either with or without melatonin. In the melatonin group, the one-year survival rate was 43 percent compared with 6 percent in the group without melatonin.
"The most important thing is that they are very promising results," says Berk. "But they have not been well established in other trials." Most attempts to reproduce the findings have been inconsistent. However, melatonin has been shown to enhance the effectiveness of conventional cancer therapies, including radiation and chemotherapy.
"The problem with chemotherapy, surgery and radiation is that for the most part they are very toxic," says Dr. David Blask, MD, PhD, senior research scientist in the Experimental Neuro-Endocrinology Lab at the Bassett Research Institute in New York. Melatonin protects white blood cells against radiation damage, giving the immune system a boost. "Many cancer patients do have sleep problems—if nothing else, melatonin can help them sleep and improve their quality of life," he says.
Since melatonin use and production varies throughout the day, the fundamental question becomes when to administer the hormone for the most effective results. The secretion of melatonin peaks in complete darkness, between 2am and 4am, and declines thereafter throughout the following 24-hour period.
"If you enter light in darkness, even a very brief exposure, it will shut off the pineal gland's ability to make melatonin," says Blask. "If you prolong that inhibitor (the light), melatonin will stay low." (Translation: if you have to go to the bathroom in the middle of the night, it's better to go in the dark.)
According to Blask, light at night suppresses melatonin in humans and could be an additional risk factor for cancer. This is one of the theories behind the higher incidence of breast cancer among women who work primarily at night, he says. Compounding the issue is the fact that most working Americans do not get enough sleep. "This is a 24-hour-a-day society, and it's just going to get worse," says Blask. "More and more people are going to be exposed to light at night and compromise their melatonin levels."
Another promising aspect of melatonin is its effect on linoleic acid, a type of fat that has been implicated in the onset of various diseases, including cancer. "Although linoleic acid is important for normal structure and function of cells, it has a downside in that it acts as a stimulating factor in cancer cell growth," says Blask.
Melatonin has been shown to interfere with the uptake of linoleic acid. "We discovered serendipitously that it reduced the ability of tumors to take up linoleic acid," he says. This is an important area for further research not only because it describes a mechanism of action for melatonin, but also because it is likely to impact the onset of other diseases as well.
"Melatonin is not a magic bullet. It’s just another piece of a very complex puzzle,” says Blask. One that definitely warrants further investigation.