Resetting the Human Death Clock: The Circadian Rhythms
Understanding how the circadian rhythms affect human longevity and how we can reset them.
The ancient Greeks believed that three older women called the Fates spun the thread of human destiny and allotted a specific amount of time for every human on earth. When this time was up, Thanatos — the personification of death — appeared to humans and carried them to the underworld.
After more than 2000 years, we no longer believe that we die once the grim reaper shows up at our doorsteps. Science has shown us that we die because, over time, our bodies lose their functions.
Table of contents:
What are The Circadian Rhythms
The Suprachiasmatic Nucleus (SCN)
How are The Circadian Rhythms and Longevity Related?
Intermittent Fasting and Caloric Restriction
Key Takeaways
What are The Circadian Rhythms?
The circadian rhythms are like your own internal planner. They regulate your physical, mental and behavioural changes daily. They work based on the amount of light in your environment. As humans, we get overcome by fatigue when our environment is darker, and we get energetic when there is light.
Biological clocks produce and regulate circadian rhythms.
What are the biological clocks? They are the timing systems in your body. Biological clocks are in your tissues and organs, and they are composed of molecules (proteins) that interact with your cells.
Factors in your body produce circadian rhythms, but external factors like light can affect them.
Light can turn on and off the genes that maintain the molecules and proteins of the biological clock.
The master clock in your brain coordinates all biological clocks in your body: the master clock is called the suprachiasmatic nucleus (SCN).
To learn more about the circadian rhythms, biological clocks, master clock and SCN, visit this link.
To learn more about the genetics of circadian rhythms, visit this link.
The Suprachiasmatic Nucleus (SCN)
SCN is a structure composed of 20 000 neurons located in the hypothalamus.
The SCN responds to changes in light because the light directly travels from the eye’s optic nerves to the SCN.
Once the light arrives in the SCN, the master clock tells the other biological clocks that it is time to wake up. Thus the circadian rhythms are regulated.
To learn more about the relation of SCN and your sleep, visit this link.
How are The Circadian Rhythms and Longevity Related?
The circadian rhythms are the biological clocks in your body ticking away until your death!
Haha, I will stop with the exaggerated and morbid jokes, but research on hamsters has shown a correlation between the changes in circadian rhythm and longevity.
A research paper written by Mark W. Hurd and Martin R. Ralph in 1998 researched “The Significance of Circadian Organization for Longevity in the Golden Hamster.” This research’s objective was to see if disrupting the circadian rhythms of golden hamsters will decrease their lifespan.
They used golden hamsters whose total activity per circadian cycle had dropped below 10% of young adults. The researchers measured the total activity per cycle of the hamsters by counting their hamster wheels’ rotations. As a result, the researchers took the hamsters who completed 500 to 1000 turns per cycle.
They then split the hamsters who met this criterion into four categories: SCN graft, control graft, sham-operated and unoperated.
In the results, the control groups (those who got cortical tissue grafts, unoperated, sham-operated) continued to perform less activity. In contrast, the hamsters that underwent SCN graft transplants lived longer than the operated and unoperated control groups.
- Their longevity increased by four months.
- The death rate was less than 10% per month for the SCN recipient group (the rate of death for the control groups was 20% to 30% per month.
- On average, SCN graft recipients lived more than twice as long as they were supposed to before the transplant.
- Animal care observations also showed that the hamster with SCN grafts had improved food consumption and general appearances.
Consequently, the general health and longevity of the old golden hamsters improved by the SCN graft.
This research paper suggests that the SCN graft could have increased longevity because it had better synchronized the circadian rhythms of the hamsters, or perhaps “metabolic cost associated with maintaining circadian organization for the whole organism is increased when entrainment is compromised” (Hurd, Ralph, 1998).
The final takeaway:
“Humans, like other organisms, are rhythmic in nature, and the contribution of rhythm maintenance to overall health, longevity, and energy — especially in the elderly — should not be undervalued.” (Hurd, Ralph, 1998)
To read the full research paper, visit this link.
Intermittent Fasting and Caloric Restriction
The SCN grafts in the golden hamsters might have increased their longevity; however, we as humans cannot undergo the same procedure due to ethical issues and operational dangers.
Nevertheless, there are still so many ways we can reset our circadian rhythms to increase longevity. This article will focus on:
Caloric restriction (CR)
Intermittent fasting (IF)
A research paper by Oren Froy and Ruth Miskin, released in 2020, explores the “Effect of feeding regimens on circadian rhythms: Implications for ageing and longevity.” Their paper explains if CR and IF can impact the master clock in SCN to reset the circadian rhythms.
Caloric Restriction
In mice, rats and monkeys, CR prevents and delays age-related diseases like cancer, diabetes, kidney disease and cataracts. In humans, CR has had positive impacts on significant risk factors of atherosclerosis, type 2 diabetes and inflammation. Why CR is so beneficial is still unclear. The following theory suggests using CR to decrease mTOR signalling to SCN:
- A new theory is that ROS (H2O2), an activator of the TOR (target of rapamycin) pathway, causes ageing. The TOR pathway is like a sensor that checks how much nutrition and energy the cell has and then sends an anabolic signal that will determine the growth of the cell, its size and its metabolism. In mice, the mTOR is a signalling cascade in the SCN activated by light; this is to say that mice’s circadian rhythms link to mTOR. Scientists have found that CR has decreased the mTOR signalling in mice tissues.
Thus by using CR to decrease mTOR signalling to the SCN clock, we can reset the circadian rhythms.
Intermittent Fasting
In animals, IF has increased lifespan, improved glucose metabolism, cardio-protection, neuro-protection, and cancer resistance. In humans, IF can reduce the risk of cardiovascular diseases. It is important to note that the benefits of IF are separate from its reduction of caloric intake. Like CR, we still do not know the mechanisms behind IF that makes it so beneficial for longevity. The following experiment on mice showed that IF can change the circadian rhythms:
- When IF mice were given food during daylight, their gene expression in the liver became arrhythmic, but the rhythm established when they were given food during the night. IF can reset the SCN clock because the time of feeding and light conditions changed the circadian rhythms.
The main benefits of CR and IF are that they reset the master clock in SCN, thus resetting the circadian rhythms.
To read the full research paper, visit this link.
Key Takeaways
Understanding how we age and how we can stop the process is a very complex topic. Many biological factors stimulate the process.
The role that the circadian rhythms, biological clocks and SCN play in ageing is significant, and we research, we understand their roles more clearly.
CR and IF are two dietary regimens that can reset the circadian rhythm and increase longevity. Researchers are still exploring the mechanisms of these two regimens.
It is a matter of personal choice whether you decide to implement CR or IF into your lifestyle.
The field of longevity is evolving every day, creating new practices and treatments continually. There is still a long way ahead of us to explore the effects of the circadian rhythms on longevity. However, every day, with ever-evolving innovations and research, we get a step closer to resetting the human death clock.
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References
Thanatos: The Editors of Encyclopaedia Britannica. “Thanatos.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 28 Feb. 2011, www.britannica.com/topic/Thanatos-Greek-mythology.
The Fates: The Editors of Encyclopaedia Britannica. “Fate.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 26 Apr. 2019, www.britannica.com/topic/Fate-Greek-and-Roman-mythology.
4 types of ageing: Stibich, Mark. “How to Slow Down the Process of Aging.” Edited by Isaac O Opole, Verywell Health, 16 Jan. 2020, www.verywellhealth.com/what-is-aging-2224347.
The circadian rhythm, biological clock, master clock and SCN: “Circadian Rhythms.” National Institute of General Medical Sciences, U.S. Department of Health and Human Services, www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx.
SCN and light: “Sleep Drive and Your Body Clock.” Sleep Foundation, 28 Sept. 2020, www.sleepfoundation.org/articles/sleep-drive-and-your-body-clock.
Research paper of effect of circadian rhythm on longevity in hamsters: Hurd, Mark W, and Martin R Ralph. “The Significance of Circadian Organization for Longevity in the Golden Hamster.” Journals.sagepub.com, 1998, journals.sagepub.com/doi/pdf/10.1177/074873098129000255.
Research paper on the effect of caloric restriction and intermittent fasting on the circadian rhythms and their implications for longevity: Froy, Oren, and Ruth Miskin. “Effect of Feeding Regimens on Circadian Rhythms: Implications for Aging and Longevity.” Aging, Impact Journals LLC, 11 Dec. 2010, www.ncbi.nlm.nih.gov/pmc/articles/PMC2837202/.
