Life & Health

Struggling to fall asleep at night or feel groggy in the morning? If so, getting more sunlight exposure in the morning might help. According to experts, sunlight affects sleep and mood by influencing the body's natural rhythms and hormones.

Like temperature, food, caffeine and supplements, light influences sleep cycles and mood. Human beings have internal 24-hour biological clock, called the circadian rhythm regulating the sleep/wake cycle. 

Circadian rhythm is sensitive to light, especially in the morning and evening, and biochemically regulates the sleep/wake cycle through three different types of hormones and neurotransmitters: melatonin; serotonin; and cortisol.

Melatonin is a sleep-inducing hormone, normally produced when it is dark. Production of this hormone declines when it is bright. Melatonin levels are normally low during the day and high at night. It is called sleep hormone not because it causes sleep directly but because it relaxes the neurons (brain cells) signalling the body that it's time to hit the sack.

And exposure to sunlight can help increase the body’s melatonin levels at night by stopping the production and resetting its level in the morning. A healthy melatonin level also has the added benefit of reducing the risks of cancer and bone health.

Cortisol is another hormone, the production of which is influenced by sunlight. It is often called the stress hormone as cortisol levels go up when one feels stressed, automatically increasing the heartbeat and blood pressure. Cortisol levels are normally high in the morning, helping one wake up warming the body and preparing for the day. It also helps in the body’s immune function. 

However, cortisol levels should drop throughout the day, reaching their lowest point at night, allowing the body to relax and ultimately fall asleep. If cortisol levels are too high at night, one may have trouble sleeping, or experience insomnia, anxiety, or depression.

Sunlight can help lower cortisol levels at night by stimulating the body to produce more cortisol in the morning. This creates a healthy cortisol rhythm matching the sleep/wake cycle.

Serotonin is a neurotransmitter, meaning it helps in transferring messages (signals) between neurons. Human brains on average are said to have 120 billion neurons.

It plays an important role in mood and well-being. Also called a natural “feel good” chemical, it makes one feel emotionally stable, more focused, motivated and happy. Serotonin appears also to play a role in regulating appetite, and digestion.

Low serotonin levels, on the other hand, can lead to a variety of mood swings and disorders, including depression.

When eyes are exposed to sunlight parts of retina become stimulated cuing the human brains to produce serotonin. Serotonin has a very vital role, in that it helps produce melatonin in human bodies. Hence, keeping the serotonin level balanced is key to a good night’s sleep.

By getting sunlight in the morning, the body synchronises with the natural day/night cycle, making one feel more alert during the day and sleepy in the evening. This can improve sleep quality and duration, as well as mood and energy levels.

Disclaimer: This article is inspired by different episodes of the Huberman Lab podcast, by Dr Andrew Huberman, Professor of Neurobiology and Ophthalmology at Stanford School of Medicine. Some suggestions here are taken from various TED Talks and podcast episodes of Dr Matt Walker, Professor of Neuroscience and Psychology at the University of California, Berkeley, USA These tips and bio hacks are grounded in science and are helpful to everyone but it is not a substitute for medical treatment for insomnia and sleep apnea. Consult and follow the medical advice from doctors for that matter.