Light, sleep and mood - how are they related?

You know the weather that makes you feel joyful, cheerful, full of strength and energy? And the kind makes you want to wrap yourself in a blanket, cancel all your responsibilities and fall asleep? Of course, personal preferences can be very different, but on average, we are most active and joyful in sunny weather, and sleepy and melancholic when it's cloudy. And if you wondered who is to blame for your lack of strength on sunless days - the perpetrator is your pineal gland.

The pineal gland is a neuroendocrine gland located in the brain. It got this name because of its appearance (from the Greek word "epiphysis", meaning "growth, lump"). The pineal gland hormones are responsible for circadian biorhythms (fluctuations in the intensity of biological processes associated with the change of day and night), regulating nervous system functioning, and affecting metabolic processes. The most interesting hormones of the pineal gland for us are melatonin and serotonin. 


One of the main actions of melatonin is to regulate sleep. In humans, up to 80% of melatonin is produced in the pineal gland. The secretion of this hormone is strongest at night; during the day, the synthesis of melatonin decreases. Darkness stimulates the production of this hormone, while light acts as an inhibitor. Actually, it is thanks to this hormone that a full night's sleep and restoration of our body at this time are possible. Since light blocks the production of melatonin, it is important to sleep in the dark.


Serotonin is synthesized during daylight hours and accumulates in the pineal gland. This hormone regulates a huge number of processes in the body, from digestion and the reproductive sphere to the general feeling of satisfaction and happiness. It's even called the "happiness hormone". Adequate amounts of serotonin are essential for a good mood and normal performance. Also, serotonin is necessary for the production of melatonin at night and, accordingly, it indirectly affects our ability to get enough sleep and recover through the night.

As you see, our pineal gland is very sensitive to light. When there’s light all around - it's time to produce serotonin, rejoice and create. When it’s dark out - time for melatonin, rest and a reboot. This scheme works great when there is a lot of sun during the day and darkness at night. But when cloudy days arrive, serotonin production decreases and your mood deteriorates.

So what to do?

  1. Sleep at night and stay awake during the day. Remember that melatonin is only produced in the dark, which means that your quality of rest during the day will be much lower.
  2. In the absence of natural sunlight outside your window, surround yourself with artificial light and don’t work in the darkness.
  3. Eat foods high in glucose (needed for the production of serotonin) and tryptophan (the amino acid that makes serotonin). This includes dairy products (especially cheese), dates, plums, figs, tomatoes, soy, and dark chocolate - yum!

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