CIRCADIAN RHYTHM – What is it? And why is it so important?

Your circadian rhythm is vital for your well-being. It is an ancient system. We evolved to be in tune with the cycles of the earth. Everything is built around the sun and the 24 hr cycle. Light guides everything, every cell in your body. Your mood, when you get hungry and when you sleep…

These circadian rhythms developed 300,000 years ago. We have been using artificial light for just a few hundred years…

The cells in our bodies are on different schedules. Some are active while others rest and vice versa. You need light information in every cell in the body…

The neurons in your eyes are not just for seeing stuff, they also convey light information to the brain which controls mood, body temperature and lots of other stuff.

The key thing to reset your circadian clock is to get natural light into your eyes early in the day. If there is cloud cover you may need a bit more time. Anywhere from 2 to 10 mins. Even if it is a dull old day, the photons (light energy) still get through.

Your body will release melatonin 16 to 18 hours after seeing light. Melatonin makes you sleepy.

Bright light too late – body thinks it’s out of sink and delays sleep.

Bright light too early – body thinks it’s out of sink and wakes you up early.

The best way to regulate ourselves is through appropriate exposure to light. Light during the day AND natural evening light to a certain extent helps to buffer our exposure to bright light later on.

Your circadian rhythm is linked to happiness and here is why – Light during the day affects a structure in the brain called the habenula, which is responsible for pro-depressive circuits. Light prevents the habenula from suppressing the release of stuff like dopamine, which makes you feel good. So, the right light at the right time suppresses the activity of the habenula. Lots of things affect the habenula, light is one of the most important. Behaviours that increase serotonin such as feeding and socializing, cuddling and smiling also suppress the habenula. Get smiling and cuddling people!

Bright light between the hours of 11pm and 4am activates the habenula and therefore the depressive circuit. It also has an effect on our memory and learning capacity.

Your circadian rhythm is also linked to weight gain and over-eating – Because of light, you eat at certain times, your body will lock on to that schedule. If you remove light, you will throw off the circuitry that controls feeding and your body won’t know when to tell you to eat.

Along with the habenula, light also signals to the intergeniculate leaflet, an area near the thalamus. This controls hunger and metabolism. The light coming into your eyes controls when you get hungry and your metabolism. Therefore, it is tuned into correct functioning of pancreas, insulin excretion etc.

What you need to do…

Avoid bright light 2 hrs before bed, candles/lights physically low in the room

Reset your circadian rhythm – get out and see a sunrise and sunset x2 days – this will restore cortisol and melatonin levels.

Do not look at your phone/computer/tablet at night, never between 11pm and 4pm.

Do not eat late.

For more on this…
Andrew Huberman

Samer Hattar

Exposure to Light at Night May Cause Depression, Learning Issues, JHU Biologist Says

For most of history, humans rose with the sun and slept when it set. Enter Thomas Edison, and with a flick of a switch, night became day, enabling us to work, play and post cat and kid photos on Facebook into the wee hours. However, according to a new study led by Johns Hopkins biologist Samer Hattar, this typical 21st- century scenario comes at a serious cost: When people routinely burn the midnight oil, they risk suffering depression and learning issues, and not only because of lack of sleep. The culprit could also be exposure to bright light at night from lamps, computers and even iPads.

jo stephens