1 Lighting and Melatonin: How Lighting Impacts Melatonin Suppression and Regulation Evan Bailey Brigham Young University Summary Melatonin has long been an important element in the function of the human body. Recently however, an increasing amount of research has raised fundamental questions about melatonin s exact function and benefit in the body. As mankind advances and civilizations become more industrialized, the basic human environment has changed and will continue to change if not controlled. Some studies have reported the negative effects that man-made lighting is having on the production and regulation of melatonin. Science must be able to discover and correct any harmful correlations between poor lighting and health. Introduction Melatonin has been recognized for many years as the sleep hormone in the body. It is widely held that the body needs melatonin in order to receive an adequate amount of sleep and rest. Melatonin is also responsible for other functions in the body that are required if the body is to remain in homeostasis. In addition to these important functions, more is now understood as to how natural and artificial lighting can affect melatonin release and suppression. To better understand melatonin and its functions, it is important for individuals to understand what can trigger the release or suppression of this powerful hormone. As one understands the roles and functions of melatonin, it may be easier to perceive and appreciate the possible health risks associated with suppression. Society has experienced many changes in work environments over the last 100 years as occupations have changed with more people working indoors for most of the day. There are some simple things, however, that individuals can do to balance their melatonin levels and live a healthier and happier life. Why Melatonin? As described, melatonin plays many different roles in helping the body maintain homeostasis. Without the presence of melatonin, the body would struggle to survive. To understand
2 melatonin better, it is important to understand how it is triggered to be released into the blood stream. The release of the hormone is the result of several different signals and reactions in the brain. The process is started when the retina in the human eye detects a light source. Within the retina are tiny cells called melanopsin ganglion cells, whose purpose is to act as photo sensors and detect levels of light and darkness (Brown & Robinson, 2004). The light and dark signals are then sent to another important part of the body: the Suprachiasmatic nucleus or SCN. The SCN is a part of the hypothalamus region in the brain that is responsible for controlling the body s circadian rhythm. When the darkness signal is sent to the SCN from the melanopsin ganglion cells, the SCN then sends a signal to the pineal gland which secretes melatonin. The melatonin then enters the blood stream and helps the body to eventually achieve a sleep state (UMM, 2007). This process is then repeated in the morning except that the SCN signals the pineal gland to stop melatonin production. Research is still being performed to determine how sensitive the body is to variability in light exposure. Too much melatonin in the body during the day would cause a person to be drowsy and too little at night would result in sleep disruptions. Melatonin Functions Melatonin has many functions other than assisting with sleep. The body has additional needs that also must be addressed by melatonin. If the light and dark cycle is disrupted and there is too much melatonin or not enough, many body systems will not function properly. Biological Clock As briefly discussed earlier, melatonin helps maintain the human biological clock or circadian system. This important system helps the body know when to wake and when to go to
3 sleep. Sometimes, a person s biological clock is out of sync with the normal light and dark periods during a 24 hour period. This example of confusion can be seen in night shift workers and people who travel abroad. Fortunately, there are ways of adjusting a person s biological clock through light therapy, which suppresses melatonin production to a later time. Research has shown that the biological clock is more sensitive to some light than others. Melatonin suppression is most successful using short wavelength light sources such as blue light (Rea et al, 2002). A blue short wave light is the color most commonly found in natural sunlight. When a person is exposed to this color of light at high intensity, there is usually little or no melatonin produced in the body. As a result, the person will experience more energy. In the evening, if a person has a healthy biological clock, melatonin will start to produce as the sun goes down or when lights are turned off. Immune System The immune system is another important bodily function related to melatonin. Studies have shown that melatonin serves as an antioxidant in the body aiding in the regulation of antioxidant enzymes (Navara & Nelson, 2007). It has also been demonstrated that melatonin plays a role in preventing acute and chronic inflammation in the body. For example, melatonin is associated with reductions of septic shock among infants (Carillo-Vico et al, 2005). Sleep and Behavior As discussed, melatonin helps the body sleep. In some people however, their bodies do not always function as designed. Specifically, their bodies may not respond to light in the same way compared with healthy sleepers. These people may not experience the same melatonin release or production, which then has an impact on the amount and quality of sleep. For example, people with attention-deficit/hyperactivity disorder (ADHD) and Alzheimer s disease suffer from frequent sleep disturbances. In order to help those with sleep disturbances better control melatonin in the body, light therapy is often used to reset the body s biological clock. Studies have shown great improvements in sleep quality when using blue light therapy a few hours before bedtime
4 (Figueiro et al, 2002). There are many ways that indoor lighting and light therapy can regulate melatonin through new lighting technology. Melatonin Problems New studies are emerging that show some correlation between health problems and low or non-existent levels of melatonin. A recent study by Srinivasan (2007) suggested that melatonin helps control the amount of estrogen in the body. When melatonin is not present, estrogen levels are higher which is associated with a greater chance in the development of cancer cells. A 10-year study was performed among nurses employed in night shifts. After controlling other determinants for cancer, the results showed that nurses that worked at least three night shifts per week over an extended period of time were much more likely to develop breast cancer than those that worked a normal day shift (Schernhammer et al., 2001). These results have led to the melatonin hypothesis, which suggests a possible link between a lack of melatonin and cancer production. More studies in this area are still being performed, but there is some correlation between nighttime light exposure and the development of breast cancer. More studies have shown other possible links between nighttime lighting and breast cancer. Industrialized well-lit nations show a much higher rate of breast cancer cases compared with developing nations with limited lighting sources (Navara & Nelson, 2007). Another study showed that blind women have a 20% less chance of developing breast cancer and often experience more regular melatonin levels (Navara & Nelson, 2007). There are many factors that can be linked to breast cancer among men and women, but research continues to suggest some correlation between a lack of melatonin and cancer production. Light in Society As America and other industrialized nations continue to advance, a 24-hour society is immerging. Many common businesses appear to stay open later as customers appear to be shopping at later hours. This often means that many employees are also working later into the evening. Research has shown that 15% of America s work force has a shift later than the normal 9-5 work day (Navara & Nelson, 2007).
5 This nighttime lifestyle of working, shopping, and socializing could be taking a toll on the health of Americans by suppressing their melatonin production. Light pollution appears to be a growing problem as the nation s population increases. Americans are being exposed to lights later in the day through business and street lighting. For those that live in busy downtown areas, it may be difficult to get the needed dark nighttime environment that would allow melatonin production. In addition to the lighting problems in the outside environment, there is a big problem with the quality and color of the lighting now present in the average American households and businesses. Most household and business lighting does not contain a natural wavelength or brightness that is needed to adequately suppress melatonin. If melatonin is not suppressed, people can experience depression and other side effects such as eating disorders and mood swings (Cleveland, 2007). The opposite effect is also true at night where lighting is often too bright causing the body to slow down melatonin production. Possible Solutions As more studies demonstrate a correlation between lighting and melatonin, society will need to be educated if changes are to be made. Many Americans pay little attention to the amount of light they receive during the day, when they come home, or in the evening hours. Most Americans today are unaware of the health problems associated with melatonin irregularity. Health education programs will need to be developed to inform and teach people about the impact that lighting has on health. New lighting technology is now being introduced into the market that may help solve some of the problems that society is facing with lighting. Natural full spectrum bulbs are available which simulate a more natural blue color
6 which could help to suppress melatonin during the day. Many people are turning to compact fluorescent lighting to save energy, but most of these lights cannot be dimmed which limits their use for healthy lighting. Due to the limitations with traditional lighting, a new avenue of lighting is already immerging through the development of light emitting diode lighting, or LED lighting. LEDs can be designed to produce any desirable color and brightness level. This new lighting technology has the opportunity to make lighting healthy and control the release and suppression of melatonin. LEDs will provide the opportunity for flexible healthy lighting options for every American home and business. Summary Melatonin is an essential hormone that the body needs in order to remain healthy. Melatonin is released into the blood stream to help the body fall asleep and serve as an antioxidant to prevent the development of cancer cells. More research and information is now available about melatonin and its importance in the human body. Through this information, the importance of how melatonin is produced and suppressed has been gaining attention. It is established that melatonin is produced when ganglion cells in the retina detect a lack of light. The morning bright light that stops the production of melatonin in the body is essential to the health of every American. The body s biological clock needs to be maintained to control the melatonin release cycle. Modern-day outdoor and indoor lighting is starting to cause disruptions in the melatonin production in the body. New lighting technology may be able to solve many of the problems experienced with melatonin disruption. New LED lighting will play an important role in improving the lighting environment of homes and businesses which will improve melatonin regularity. These improvements will be available only if the individual will recognize the problem and make improvements in their lighting choices. Conclusion Melatonin is getting more attention in the eyes of the medical industry and many important research studies have been performed. Problems with lighting are finally being addressed which will hopefully lead to important
7 changes in lighting environments. More research is still needed to be able to better link a lack of melatonin with health risks. If appropriate changes are made, the health of many Americans will change for the better.
8 Literature Cited Primary Sources 1) Figueiro, Mariana G., Eggleston, Gregory, & Rea, Mark S. (2002). Effects of light exposure on behavior of Alzheimer s patients. Light and Human Health. 151-156. 2) Schernhammer, Eva S., Laden, Francine, Speizer, Frank E., Willett, Walter C., Hunter, David J., & Kawachi, Ichiro (2001). Rotating night shifts and risk of breast cancer in women participating in nurse's health study. 93, 1563-1568. Secondary Sources 3) Brown, AuthorR Lane, & Robinson, Phyllis R (2004). Melanopsin-shedding light on the elusive circadian photopigment. Chronobiology International. 21, 189-204. 4) Cleveland, Amber (2007, Sept 5). Researchers Developing Device To Predict Proper Light Exposure for Human Health. Retrieved Sept 6, 2007, from Rensselaer News Web site: http://news.rpi.edu/update.do?artcenterkey=2303&setappvar=page(1). 5) Carillo-Vico, Antonio, Guerrero, Juan M., Lardone, Patricia J., & Reiter, Russel J. (2005). A review of the multiple actions of melatonin on the immune system. Endocrine, 28, 189-200. 6) Navara, AuthorKristen J., & Nelson, Randy J. (2007). The dark side of light at night: physiological, epidemioglogical, and ecological consequences. Journal of Pineal Research. 43, 215-224. 7) Rea, Mark S., Bullough, John D., & Figueiro, Mariana G. (2002). Phototransduction for human melatonin suppression. Journal of Pineal Research. 32, 209-213. 8) Schernhammer, Eva S., Laden, Francine, Speizer, Frank E., Willett, Walter C., Hunter, David J., & Kawachi, Ichiro (2001). Rotating night shifts and risk of breast cancer in women participating in nurse's health study. 93, 1563-1568. 9) Srinivasan, V, Spence, DW, Pandi-Perumal, SR, Trakht, I, Esquifino, AI, & Cardinali, DP (2007). Melatonin, environmental light, and breast cancer. 10) UMM, (2007). Melatonin. Retrieved October 9, 2007, from University of Maryland Medical Center Web site: http://www.umm.edu/altmed/articles/melatonin-000315.htm.