The world today operates on a 24/7 basis no matter where you are in the world or the time. The most notable instance of this includes shift workers at hospitals or pilots operating planes in the dead of night. However, while these individuals work according to these specific schedules, the circadian rhythms of the body do not. The circadian clocks of our bodies operate on their own rhythm and there are many instances where we can impact that clock. For example, staying up late at night, eating food late, or napping during the day could impact the circadian rhythms of the body in many ways. Dr. Turek, during his talk at Loyola University Chicago, discusssed how disruption of circadian rhythms in different parts of our body is affected. Prior to Dr. Turek’s talk, what piqued my interest was the research he discussed alongside Dr. Summa in a chapter of a textbook. The discussion concerned the promotion of a specific enzyme called histone deacetylase 3 (HDAC3) outside its circadian rhythm that causes adverse effects, more specifically how consumption of high fat foods excited HDAC3 outside of the standard clock in the intestinal epithelium and promotes transcription and expression of a gene that promotes lipid uptake and cause obesity. This made me question whether a similar dysfunction occurred with how later in the night there is an upregulation of the hormone ghrelin that promotes hunger. After Dr. Turek’s talk, I asked him if that was true. Dr. Turek said that is the general idea, but more specifically that during the evening, the hunger-suppressing hormone, leptin, is released. If you are awake later in the night though, leptin production will decrease and there will be an upregulation of ghrelin.
Being in college, I have been surrounded by peers that have utilized energy drinks such as Monster, Reign, and Celsius to stay awake at night and study. This has led me to the question: How does the consumption of caffeine disrupt the circadian rhythm of sleep? In an article by Reichert et. al. titled “Wide awake at bedtime? Effects of caffeine on sleep and circadian timing in male adolescents – A randomized crossover trial”, they aim to add some insight to this question. In this article, Reichert et. al measured the effect of caffeine on the circadian timing of slow-wave sleep (SWS) in adolescent males via the use of an electroencephalogram (EGG). During the day, the researchers disallowed the adolescents to take naps or eat or drink anything that contained caffeine. Five hours prior to their bedtime, the researchers randomly gave an adolescent either a capsule containing a placebo or caffeine and during the night cycle had their EEG recorded. The researchers discovered that consumption of caffeine reduced SWS. This result was most significant in those that had larger SWS than others during the placebo phase of the experiment. This is to say that caffeine consumption, at 80 mg or more, causes more reduction in adolescents that rely heavily on sleep. This is also to say that consuming this much caffeine can disrupt the circadian rhythmicity in SWS. Because of this, it would be important to avoid consuming 80 mg of caffeine to avoid that reduction in SWS which would lead to daytime sleepiness. Understanding this study could bring both reason and caution to those that consume a lot of caffeine in the evening, especially those who are college students. If one is constantly tired throughout the day and has more than a cup of coffee or any energy drink in the evening a few hours prior to going to bed, there may be an explanation for this. It is likely that the caffeine consumption at such later hours causes our bodies to disrupt its natural circadian clock. Changing the time to when you consume caffeine can lead to better sleep and potentially other circadian functions in your body.
References:
Reichert, C. F., Veitz, S., Bühler, M., Gruber, G., Deuring, G., Rehm, S. S., Rentsch, K., Garbazza, C., Meyer, M., Slawik, H., Lin, Y. S., & Weibel, J. (2021). Wide awake at bedtime? Effects of caffeine on sleep and circadian timing in male adolescents - A randomized crossover trial. Biochemical pharmacology, 191, 114283. https://doi.org/10.1016/j.bcp.2020.114283
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