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Circadian Rhythm refers to the physiological, psychological, and behavioral patterns that living beings experience according to their respective biological clock. All the living beings including humans, plants, animals, and even the single-celled species follow a circadian or biological clock.

This internal clock runs on a twenty-four-hour cycle, which is essentially the length of one cycle of day and night. Our internal clock syncs with the external environment via the signals of temperature, humidity, and light!

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Exposure to daylight can speed up or slow down our biological clock!

Out of the three signals, light or more specifically sunlight is the primary factor that guides proper functioning of our biological clock and hence regulates our circadian rhythm.

This is the primary reason, why proper exposure to natural light is essential for all living beings. Sunlight or natural light acts as the cue to synchronize our biological/circadian clock, hence regulating all bodily functions!

Each cell of our body has its own biological clock

Biological clocks are found in every cell of our body. The cell clusters, hence respectively guide the functioning of their specific tissues, which in turn guide the functioning of their specific organs, and hence the body.

The cellular circadian clocks are made up of proteins that interact with the cells to guide their functioning. The genes of these proteins are turned on and off by the daylight exposure through a master clock.

Circadian Rhythm - SCN
The Master Clock is located inside our brain

The Master Clock behind Circadian Rhythm – The SCN

The trillions of cellular biological clocks are regulated by the master clock, which is termed as suprachiasmatic nucleus – SCN. It is a group of nearly 20,000 nerve cells and is located in the brain.

SCN receives direct input from the eye, hence acts as a link between light and timing! It receives light signals from the outside world and shares with the rest of the body cells. Besides the eye, SCN is also indirectly connected to the:

  • pituitary gland – produces growth hormone
  • adrenal gland – releases the stress hormone
  • thyroid gland –  produces thyroid hormones
  • gonads – produces reproductive hormones
  • pineal gland – releases sleep hormones
  • hunger center in hypothalamus section of the brain – releases hunger (ghrelin) and satiety (leptin) hormones

Hence, proper functioning of SCN is central to our wellbeing! When SCN gets reset by light exposure, it actually resets the clocks of all other cells in the body. 

This is the reason why a change in day and night cycle results in changing the speed of the circadian clock or SCN and hence of all our body functions such as metabolism rate, hunger levels, sleep cycle, stress levels, our growth, and even fertility.

Disrupting the Circadian Rhythm triggers chronic mental and physical disorders!

Inside the body, the biological clocks of different organs also work together to create a smooth internal rhythm termed as the Circadian Rhythm. Any disruption in the internal rhythm will either LOAD or STARVE our organs, hence affecting their functioning or destroying them completely. Our internal rhythm is controlled by four main factors:

  • Sleep
  • Food
  • Physical Activity
  • Signals from the SCN – Master Clock

For proper functioning of the Circadian Rhythm, it is essential that we take care of the optimal quantity, good quality, and also appropriate timing of the guiding factors.

If you happen to change any of these factors, the results become evident in both the short term as sub-optimal functioning and in the long term as chronic disorders such as Diabetes, Cardiovascular Disorders, Obesity, Insomnia, Stress, and Inflammation.

Circadian Rhythm-min

Relationship of Sleep with Circadian Rhythm

It has been observed that by keeping children awake past the sleep hours 9:00 PM to 10:00 PM interferes with their circadian rhythm. Such disturbances also delay their brain development.

Irregular sleeping hours and insufficient sleep disrupt the functioning of an individual’s biological clock. Insufficient sleep hours lead to:

  • Reduction in the growth hormone secretion and functioning.
  • Interruption with cleansing and elimination functions of the body – directly affecting the digestive system.
  • Interference with the repair and cell division functions which happen during sleep hours. This involves the replacement of dead cells with new cells, which are also produced while we are asleep.
  • reduced efficacy of the natural detoxification process of removal of oxidized cells. These can otherwise accumulate as plaques or toxins inside various body parts.

Insufficient and Irregular sleep hinders growth functions

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Lack of sleep, irregular hours, and lack of daylight can result in Autism and ADHD even in adults! This is the reason why we need to sleep at the same time every night and maintain at least 7-8 hours of sleep for the teens, adults, and the elderly, at least 9-10 hours for the babies, and between 8- 9 hours for the toddlers.

Relationship of Food with Circadian Rhythm

Food intake is vital for our survival! As important as it is, the first bite or the first sip of your drink signals multiple organs to get into action, hence directing our Circadian Rhythm.

If you take food at different times every day, your internal rhythm is disrupted and your brain gets confused. This further impacts the secretion of digestive juices, hormonal release, and proper assimilation of the food. This triggers multiple digestive system health issues such as acid reflux, bloating, and indigestion.

Additionally, irregular food intake is highly likely to overload or starve your organs as they might not be fully ready due to changing signals. Irregular food habits are also one of the factors behind spiking blood sugar levels.

In fact, it has been studied that it is possible to manage Diabetes by maintaining a timely window of food intake along with the type of foods consumed. 

Since every bite or beverage takes several hours to be fully assimilated and eliminated from our body, it is important that we maintain a consistent schedule to food intake.

This allows for an effective digestive system, optimal metabolic rate (which is also important for weight loss), and a regular bowel movement.

The timing of your first and last sip or morsel of the day is the key to weight loss!

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Along with a consistent schedule, it is also important that we eat early! This is because our digestive system functions much better during early evening hours than the latter part. Hence, the same food takes it longer to be digested if consumed at say 9:00 PM than 6:00 PM.

Taking early dinner is key to weight loss!!

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Relationship of Exercise with Circadian Rhythm

Use it or lose it! Apart from losing your body organs by not using them enough, lack of physical activity leads to chronic brain and body issues. Multiple muscles get activated when our body undergoes movement or any kind of physical activity.

Exercise is the key to a healthy brain and body!

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  • It allows our organs to function better by improving blood circulation, hence supplying more oxygen and nutrients to them.
  • Exercise also improves sleep and helps to align the circadian rhythm with the SCN.
  • Apart from this, physical activity releases several hormones that have a positive effect on the functioning of our brain – increases our satisfaction and happiness levels.
  • Some forms of physical activity such as Sun Salutation or Surya Namaskar Yoga help to burn fat and flush toxins out of the system.
  • It strengthens the muscles of the cardiovascular system (heart and of the artery walls) and stimulates the growth of new blood vessels, thus improving blood pressure regulation.
  • It helps with weight loss through the following actions:
    • Increases number of mitochondria that burn fat and sugar
    • Causes fat intake in muscles and not the belly
    • Increases insulin sensitivity of the muscle and fat cells
    • Stimulates Cortisol (stress hormone) temporarily and suppresses hunger hormones

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Circadian Rhythms by NIH

Circadian Clocks, Metabolism, and Disease by Hee-Kyung Hong

Sleep and Circadian Rhythms in Humans

The Circadian Code by Dr. Satchin Panda

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About the Author Nidhi Bansal

Nidhi is the Founder of Medhya Herbals. She is a passionate nature lover and a firm believer in nature's intelligence - which is Ayurveda, a science of life! She started Medhya Herbals with a mission to make Ayurveda's deep knowledge of self-healing practical and accessible. Nidhi has experienced Ayurveda firsthand, through her father Dr. Pawan Bansal, who is an Ayurvedic practitioner with more than 40 yrs. in clinical practice. Nidhi is a Chemical Engineer from IIT Delhi.

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