|Fig. 1: An image of the molecular structure of melatonin. (Source: Wikimedia Commons)|
With the increase in the number of sleep related disorders, a big focus has been placed on the role of melatonin in the sleep cycle and the associated energy effects. Many studies have focused on the use of bright light, specifically blue light, as a way in which to treat the offset in the circadian rhythm of the sleep cycle. Results of studies have shown that the presence of blue light can impact the energy levels of the human body, specifically as it relates to the secretion of melatonin. This in turn effects energy levels.
Melatonin secretion is a natural physiological response by the body. The chemical structure of melatonin can be seen in Fig. 1. A rhythm of secretion during darkness and suppression in the presence of light impacts the creation and secretion of this hormone. Melatonin has a big impact on energy levels, especially related to the energy storage in mammals.  Studies on hamsters showed that increasing the melatonin concentration in the blood stream lead to a decrease in the energy storage of the test subjects, which corresponded to weight gain as well. Similarly, the energy metabolism of the hamsters tested increased with a decrease in the melatonin concentration. This indicates that decreasing the melatonin in the blood stream, consistent with the body's natural response to suppress the secretion in the presence of light, causes the body to function at a higher energy level.  This was also seen in a study done on the energy of humans. Groups were treated with light, 4,000-7,000 lux, which increased the natural melatonin level. The subjects' energy levels were measured and calculated as the root means squared value of the activity level (measured on a scale from 0-255, based on the measurements from ambulatory wrist actigraphy monitors) while they slept and the duration of that time. The mean energy level in the treated group was 588.7, which was significantly lower that the non-treated group. The non-treated group had a lower melatonin level and a mean energy level of 745.7. This shows that an increase in the melatonin levels leads to a subsequent decrease in energy levels.  As such, understanding how to control and optimize the secretion and suppression of the melatonin for optimal hours of the day could help improve the treatment of sleep disorders and positively impact the energy levels of individuals.
|Fig. 2: The light spectrum. (Source: Wikimedia Commons)|
Blue light is a form of light with a short wavelength of between 450 - 495 nm, and thus produces a higher amount of energy, typically around 3.65 × 10-19 joules.  The spectrum of light is shown in Fig. 2. Studies have been performed on groups to show that the exposure to high intensity light, and specifically light with higher amounts of blue light, leads to an decrease in melatonin levels and a subsequent increase in alertness.  In a study conducted, participants were exposed to either compact fluorescent light, which contains high amounts of blue light, or incandescent light. Saliva samples were taken to measure melatonin levels, and cognitive performance tasks were administered to measure the participants' energy and functioning level.  The reaction time tests are most sensitive to sleep deprivation, which is tied to the melatonin secretion. These test results showed significant improvement after exposure to the compact fluorescent lights at higher powers, which was shown in the faster reaction times of participants under these conditions.  Based on these findings, it can be concluded that the high concentrations of blue light impact the melatonin secretion within the human body, indicating that blue light can be a key form of light to target in the regulation of this hormone secretion.
Based on the findings surrounding the importance of melatonin on the regulation of energy within the body, coupled with the findings regarding the impact of blue light, we can conclude that there is an area of applicability regarding the two. Blue light, in high concentrations, leads to a decrease in melatonin secretion which leads to an increase in energy levels and alertness in humans. Learning from this, blue light can be filtered out in order to increase the melatonin secretion, as is consistent with a response to darkness, to reduce the energy levels in humans. Alternatively, blue light can be used in higher concentrations, through the use of fluorescent lights, to suppress melatonin production and allow the body to respond with higher energy levels. In even further applications, the two could be used in conjunction to optimize the sleep and overall energy levels of the human body.
© Sierra Kersten. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 T. J. Bartness and G. N. Wate, "Photoperiodic Control of Body Weight and Energy Metabolism in Syrian Hamsters (Mesocricetus auratus): Role of Pineal Gland, Melatonin, Gonads, and Diet," Endocrinology 114, 492 (1984).
 D. Dawson, N. Encel, and K. Lushington, "Improving Adaptation to Simulated Night Shift: Timed Exposure to Bright Light Versus Daytime Melatonin Administration," Sleep 18, 11 (1995).
 H. Senger, ed., The Blue Light Syndrome (Springer, 1980).
 S. L. Chellappa et al., "Non-Visual Effects of Light on Melatonin, Alertness and Cognitive Performance: Can Blue-Enriched Light Keep Us Alert?" PLoS ONE 6, e16429 (2011).