By, Ryan Yost
Circadian rhythms are your body’s internal clock [1]. Our bodies have a finite amount of energy (and other resources) - we need to use it wisely! You wouldn’t want to fall asleep at 2pm or be wired at 2am. Yet we all know that feeling. So how can we control our circadian clock to improve this - to get deeper sleep at night and have more energy throughout the day?
The major knobs you can turn to help align your circadian clock are light, temperature, exercise, food intake, and pharmaceuticals [2].
LIGHT: light is the single most important setter of your circadian clock [3]. There is actually a third retinal pathway in your visual system (aside from rods and cones) - one that doesn’t have to do with vision at all! Melanopsin-retinal-ganglion cells (MRGCs) sole function is to gauge how much light is in the environment so they can report this to the suprachiasmatic nucleus (SCN) which controls the circadian rhythm [4]. These MRGCs have even been proven to have evolved BEFORE the visual system - showing that the circadian clock is biologically more important than vision itself.
So how can you use light to improve your circadian rhythm? Simply put - get light when you want to be awake, avoid light when you want to sleep. Getting light right when you wake up triggers cortisol release during the day to keep you up and eventually transitions to melatonin release at night to help you fall asleep. I literally go outside each morning and stare at the sun as I brush my teeth with a 2-minute timed-toothbrush that will not be named (no funny quips here). And natural light (NOT the beer - that can stay in your college dorm room) is best - it has the right mix of blue and yellow light to optimally stimulate the MRGCs. Note that it is best if you actually go outside - windows and car windshields refract light to move it away from that optimal spectrum. Similarly, at sunset you should get some natural light as well to signal to your body that it is the end of the day. After this you should start to minimize light exposure - yes, especially blue light. However, note that wearing blue light blockers all day is silly - you WANT blue light when you are awake. Then after you fall asleep, you should avoid light like the plague. A flash of bright light in the middle of the night can wake you up, disrupt your circadian rhythm, and even has been shown to increase depression [5].
BODY TEMPERATURE: Your body temperature plays a significant role in regulating your circadian rhythm. Core body temperature tends to be lower (about 1-2 degrees Fahrenheit) at night compared to during the day. It reaches its minimum around 2-4 hours before you wake up, signaling to the circadian clock that a new day is about to begin. Modulating body temperature can influence alertness or sleepiness, often through compensatory mechanisms. For example, cold exposure (such as ice baths) in the morning not only wakes you up due to the adrenaline rush but also stimulates your body to generate more internal heat, indicating that you are in an awake state and require more energy [6]. Conversely, falling asleep in warm, cozy environments allows the external warmth to compensate for the body's reduced need to produce heat, signaling that it is time for sleep.
EXERCISE: exercise can also be a cue to your body’s circadian clock [7]. Engaging in physical activity, especially in the morning, can help reinforce the body's natural rhythm by signaling the start of the active phase of the day. Exercise prompts the release of cortisol and adrenaline, and it also elevates heart rate. On the other hand, exercising too close to bedtime can have the opposite effect. Evening or nighttime exercise can stimulate the body and increase physiological arousal, making it more difficult to wind down and fall asleep.
FOOD INTAKE: The autonomic nervous system consists of two primary divisions - the parasympathetic ("rest and digest") and the sympathetic ("fight or flight"). Consumption of a large meal typically stimulates the parasympathetic system, which can lead to feelings of lethargy, commonly experienced as a mid-afternoon slump[8]. Certain foods, particularly those rich in carbohydrates, can intensify this effect. Nevertheless, it seems that the body sometimes must prioritize between rest and digestion. As such, it is advisable to avoid consuming a large meal shortly before bedtime, allowing your body to concentrate on restorative sleep rather than the energy-intensive process of digestion.
PHARMACEUTICALS: Caffeine can serve as an effective stimulant, enhancing alertness and warding off sleepiness. However, its consumption should be limited in the hours leading up to bedtime. Tolerance to caffeine can vary significantly among individuals - I can drink a coffee at midnight on road trips and fall asleep at my destination at 2am no problem, while others report disturbed sleep anytime caffeine is consumed after noon. Some people use melatonin to help them fall asleep - though I don’t personally recommend it. While melatonin can assist in initiating sleep, it may not promote the optimal balance of different sleep stages, and it can lead to a variety of side effects[9]. I know that when I used to take melatonin I would wake up groggy and in a daze.
NEUROMODULATION: if only there was a non-pharmaceutical way to help you fall asleep. That’s where Elemind comes in! Our clinically proven and rigorously tested headband uses your natural brain waves to produce sounds designed to help you fall asleep. With no side effects or morning grogginess! To learn more about the science behind Elemind and how to try it out yourself - check out www.elemindtech.com/learn .
Hopefully this blog served as an interesting introduction to circadian rhythms. It should help you think more about how your behavior during the day affects your sleep at night - and give you some tools to correct any bad habits. In another blog, I will dive deeper into what can go wrong when the circadian rhythm is maligned - including circadian rhythm disorders, and shift work.
WORKS CITED
[1] National Institute of General Medical Sciences, "Circadian rhythms," [Online]. Available: https://www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx. [Accessed: 05-May-2023].
[2] S. M. Abbott and K. J. Reid, "The influence of environmental factors on sleep and circadian rhythms," in Sleep Disorders Medicine, S. S. Chokroverty, Ed. Springer, 2015, pp. 143-152, doi: 10.1007/978-1-4939-2089-1_12. [Online]. Available: https://link.springer.com/chapter/10.1007/978-1-4939-2089-1_12. [Accessed: 05-May2023].
[3] M. Münch, "Light and chronobiology: implications for health and disease," Dialogues in Clinical Neuroscience, vol. 19, no. 4, pp. 311-323, Dec. 2017. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5824141/. [Accessed: 05-May-2023].
[4] M. T. Do and K. W. Yau, "Intrinsically photosensitive retinal ganglion cells," Physiological Reviews, vol. 90, no. 4, pp. 1547-1581, Oct. 2010, doi: 10.1152/physrev.00013.2010. [Online]. Available: https://journals.physiology.org/doi/full/10.1152/physrev.00013.2010. [Accessed: 05-May-2023].
[5] T. A. LeGates, D. C. Fernandez, and S. Hattar, "Light as a central modulator of circadian rhythms, sleep and affect," Nature Reviews Neuroscience, vol. 15, no. 7, pp. 443-454, Jul. 2014, doi: 10.1038/nrn3743. [Online]. Available: https://www.nature.com/articles/nrn3743. [Accessed: 05-May-2023].
[6] K. Krauchi and T. Deboer, "The interrelationship between sleep regulation and thermoregulation," Frontiers in Bioscience, vol. 15, pp. 604-625, Jan. 2010, doi: 10.2741/3630. [Online]. Available: https://www.bioscience.org/2010/v15/af/3630/fulltext.php. [Accessed: 05-May-2023].
[7] S. D. Youngstedt, "Effects of exercise on sleep," Clinics in Sports Medicine, vol. 24, no. 2, pp. 355-365, Apr. 2005, doi: 10.1016/j.csm.2004.12.003. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S0278591904001385. [Accessed: 05-May-2023].
[8] R. B. Kanarek, "Psychological effects of snacks and altered meal frequency," British Journal of Nutrition, vol. 77, no. S1, pp. S105-S120, Jan. 1997, doi: 10.1079/BJN19970107. [Online]. Available: https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/psychological-effects-of-snacks-and-altered-meal-frequency/8E49BA864A3A4703B79C6E0A1DABDF6A. [Accessed: 05-May-2023].
[9] F. Auld, E. L. Maschauer, I. Morrison, D. J. Skene, and R. L. Riha, "Evidence for the efficacy of melatonin in the treatment of primary adult sleep disorders," Sleep Medicine Reviews, vol. 34, pp. 10-22, Aug. 2017, doi: 10.1016/j.smrv.2016.06.005. [Online]. Available: https://www.sciencedirect.com/science/article/pii/S1087079216300371. [Accessed: 05-May-2023].