The majority of people carry out their daily routine without understanding how the timing of their habits and actions have a domino effect on how they feel, look and behave.

This is because they fail to understand the importance of circadian biology and that it underpins health, performance and wellbeing.

Once you understand what your circadian rhythm is and how to optimise it, you realise that in reality you don’t need to make huge changes in your life. You just need a routine that is intentional. 

 

This article includes:

-        What is a circadian rhythm?

-        Why is light important?

-        Why is your circadian rhythm important?

-        6 top tips to optimise your circadian rhythm

 

What is a circadian rhythm?

 

A circadian rhythm is the internal body clock that regulates bodily functions over a 24 hour period.

 

Examples of processes that have circadian rhythmicity include:

●      Sleep / wake cycle – sleep anticipation in the brain default mode network (DMN)

●      Hormones – e.g. insulin, melatonin, cortisol, leptin

●      Immune system activity – e.g inflammatory substances such as TNF (tumour necrosis factor)

●      Body temperature – reaches peak during middle of day and minimum point at night

The master clock of our circadian rhythm lies in the brain, specifically in the hypothalamus there are a bunch of brain cells called the suprachiasmatic nucleus (SCN).

 

We also have circadian clocks in most organs throughout the body, like the gut, liver, pancreas, fat and muscle tissue - these are called peripheral clocks.

 

To be healthy and feel great, the master clock needs to be aligned with the peripheral clocks and they need to be aligned with our solar 24 hour day and night.

 

Why is light important?

 

There are specific factors that can influence and set our circadian rhythm - in German, this is called  “zeitgeber”! The most powerful zeitgeber is light.

 

The pathway for light to the master clock is through entering the eye.The master clock is attached to the retina and detects light (specifically blue light) which it uses to inform the body whether it is day or night.

 

This is how light synchronises our master clock to the day-night cycle!

 

The master clock then communicates with the peripheral circadian clocks throughout the body, coordinating them to also be in sync with the day-night cycle.

 

This is why viewing daylight in the morning is such a popular hot topic - more about this later.

 

Why is your circadian rhythm important?

 

The body thrives on cyclical rhythm - everything in biology does. There are times for activity and times for rest, for example, you need to be awake but you need to sleep, you need to eat but you need to fast, and you need to work but you need to rest.

 

All these processes in the body need to be coordinated to be able to operate optimally - this is what having a synced circadian rhythm allows.

 

When your circadian rhythm isn’t synced, you neither feel nor perform at your best. You might feel low in energy, struggle with your mood, productivity or weight and develop a chronic disease like type 2 diabetes or depression. (REFERENCE).

This can happen when we stay up late/ indoors / on our phones or laptops,  drink lots of caffeine and neglect our eating habits. This starts to confuse our internal body clock and cause misalignment.

 

Therefore we need to sync the habits that can influence the regulation of our circadian rhythm.

 

6 top tips to sync your circadian rhythm

 

1. Get outdoors first thing upon waking: prioritise getting outdoors within the first 60 mins or so, and get outside for some fresh or air or ideally a walk for 20 mins or so. This will help sync your circadian rhythm so you feel alert and focused for the day and sleep better at night.

2. Eat at set times in accordance with daylight: one other zeitgeber is food. This will improve your hunger and fullness signals, as well as pre and post meal processes. Eating when it is daylight is associated with better health outcomes than when it is dark.

3. Get outdoors again - ideally in the afternoon:  viewing sunlight in the afternoon/evening again communicates to your master clock that it is evening and time to begin the process of transitioning to sleep that night.

4. Practise a consistent wind down sleep routine: going to bed at the same time is a great signal for syncing our circadian rhythm. Following a wind down schedule, avoiding stimuli and devices, to wind down ready to sleep.

5. Beware of caffeine: which will keep you up. So if using caffeine, limit it to 1-2 cups earlier on in the day, so that you have sufficient time to metabolise it so that it won’t keep you up!

6. Avoid bright light in the evening: which could negatively impact your mood and make sleep harder. 

 

By Antonia Osborne, MSc, RNutr @antoniaosbornenutrition

 

References

Partch et al. (2014). Molecular architecture of the mammalian circadian clock.

Panda (2016). Circadian physiology of metabolism.

Scheer et al. (2009). Adverse metabolic and cardiovascular consequences of circadian misalignment.

Segers & Depoortere (2021). Circadian clocks in the digestive system.

Qian et al. (2018). Differential effects of the circadian system and circadian misalignment on insulin sensitivity and insulin secretion in humans.

Manoogian & Panda (2017). Circadian rhythms, time restricted feeding & healthy ageing

Walker et al. (2020). Circadian rhythm disruption & mental health.