Circadian Rhythm

  • Also known as the ‘body clock’ or the brain’s master clock
  • Circadian means “around the day” in latin
  • Regulates changes in physical and mental characteristics over a 24 hour period
  • Follows 24 hour cycle of the sun
  • Regulates itself based on light cues from the environment which differentiate between night and day

The importance of daylight

  • Exposure to sunlight increases the brain’s release of a hormone called serotonin which is associated with boosting mood and feeling calm and focussed
  • Regulates hormones, sleep patterns and the timing of the body clock
  • A lack of natural daylight interferes with a chemical in brain called Melatonin
  • Melatonin is also produced in the skin through sun exposure
  • Exposure to daylight/bright light can provide the same energy boost as a nap

Supplements are discouraged as high doses built up in the body can create new problems

People need to have a regular clear, daily circadian rhythm for health melatonin production


  • During the daytime, and in daylight, melatonin production stops.Peak levels tend to occur at night time and help to induce sleep
  • Melatonin is a hormone produced by the pineal gland within the brain and is the chemical which makes us feel sleepy
  • Melatonin production is driven by the master body clock
  • Melatonin is produced in response to darkness (reduced light entering the eyes) 
  • Melatonin in body sends signals to the brain that it is night time and switches off the signals that keep us awake
  • Being exposed to light at night can block melatonin production

Disruptions to Circadian Rhythm

Things that can disrupt your body clock!

  • Jet lag / travelling across different time zones
  • Shift Work
  • Blindness – retina cannot detect light
  • Lack of sunlight or natural daylight
  • Eating a big meal before bed
  • Staying awake all night
  • Sleeping in the daytime
  • Stress
  • Sleep disruption
  • Ageing
  • Chronic conditions (Alzheimer’s, Depression, Diabetes, Hypertension, Metabolic Syndrome, Cardiovascular Disease)

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