Nurturing our circadian rhythm for optimal health and performance
To cope with the predictable daily change in light and dark, almost every living organism has developed an internal timing system or a circadian clock (circa meaning around, and dian meaning day), which is approximately 24 hours long.
Our ancestors believed that our day-night cycles were guided by external environment only - the light in the morning waking us up, while moonlight was a sign to rest and sleep. In 1950, studies revealed that when subjects were cut off from the daily cycle of light and dark, they generated their own endogenous circadian rhythm in the absence of any external sunlight. They expressed a predictable pattern of prolonged wakefulness (about fifteen hours), paired with consolidated bouts of sleep(about nine hours), which concluded that ONLY an internal clock could be the reason for this predictable cycle.
Further research confirms that our biological rhythm is approximately one day (24 hrs, 15 minutes) so not precisely a ‘day’. However, the brain, with the assistance of our ocular light sensors, uses daylight to methodically reset our inaccurate internal timepiece each day, winding us back to precisely, not approximately, twenty-four hours [1].Scientists found that this is due to small cluster of cells collectively known as the Suprachiasmatic nucleus (SCN) which are located within the Hypothalamus– our Master Gland.
Each morning, bright light enters through our retina, sending signals to synchronise our master clock– the SCN. When the light resets the SCN, it sends hormonal signals to reset our clocks in the rest of our body.
Importance of maintaining circadian rhythm
Today we know that the circadian rhythm does not simply regulate sleep-wake cycles, but also influences the molecular biology of individual cells [2] and organ systems.
A study which started in 2002, has identified that every organ down to the cellular level has its own circadian rhythm, and thousands of genes turn on and off at different times of the day synchronising our various internal clocks. For example, our hunger and satiety pathways are circadian, so when synchronised, we optimise the nutrient flow and close the door when we are full, avoiding cravings and overeating.
Our metabolism is also circadian, so disrupting it will affect the use and storage of carbohydrates, fat and protein, amplifying many chronic conditions including obesity.
Cellular maintenance (repair, cell division and cell communication), critical for aging well, is also circadian, and our cells work together to repair, cleanse and rejuvenate in order to communicate effectively, which waxes and wanes throughout the daily cycle.
All the ‘clocks’ work together harmoniously affecting our leading rhythms of metabolism, physiology and behaviour, which organise our life into segments of
- Sleep
- Food intake
- Physical activity
at specific times of day. These interrelated rhythms form the essential foundations of our health and are entirely in our control.
We therefore function at our very best when our lifestyle is aligned with this perfectly designed inner rhythm. When one rhythm is disrupted, the others are ultimately disturbed, creating a downward spiral which, if sustained can lead to poor mental and physical health.
Life style changes that have occurred in response to technological advances over the past century resulted in unprecedented changes in seasonal timing and duration of light exposure, which in turn has been the major contributor de-synchronising our circadian rhythms. Increased prevalence of disrupted circadian rhythms strongly correlates [3] with the increased incidences of mood disorders, anxiety, premature aging, diabetes, cardiac arrhythmias, immune deficiencies, hypertension and many other lifestyle diseases.
Simple techniques to improve and nurture circadian rhythm
- Enjoy as much natural light as possible for at least 10 minutes after waking up. If it’s cloudy, or if you’re sitting by a window, extend your exposure to 20-30 minutes. This triggers your SCN to signal to your brain it’s daytime and resets your circadian rhythm for the day.
- Avoid eating late at night. Due to daily circadian rhythms regulating metabolism, consider eating your evening meal as early as possible – ideally around 6:00/7:00 pm, and avoid late night snacking.When you eat matters [4].
- Embrace soft lighting. As we cannot avoid artificial light in the evenings, using subtle lighting with soft amber, gold or red lightbulbs is ideal as not to disrupt the body’s natural melatonin production.
- Protect your self from blue light. Avoiding blue light exposure after sunset is important to support your SCN as not to disrupt your circadian rhythm. Blue light blocking glasses and protective films for all screens are available to protect you if you work after sunset.
References
- https://www.nature.com/articles/s41398-020-0694-0
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632990/
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4632990/
- https://pubmed.ncbi.nlm.nih.gov/32108181/
