Have you ever wondered why us humans spend about 1/3 of our lives sleeping?

From an evolutionary point of view, thousands of years ago, when humans were gatherers and hunters living in hostile environments, being asleep meant being most vulnerable to predators and danger. Looking at the animal kingdom, all species engage in some sort of sleep. Sea creatures like dolphins and whales sleep with half brain at a time, with the other half awake to maintain life-necessary movement. When birds need to be vigilant during sleep, one half of the brain stays awake and one eye open. So why didn’t Mother Nature make us evolve into species that could live well with not much or no sleep at all?

In fact, sleeping is so necessary that we could live for a few weeks without any food, some days without water, but after only 2 or 3 nights without sleep our bodies start to fail. Routinely sleeping less than 6-7 hours a day (chronic sleep deprivation) depletes the immune system and increases the chances of having diabetes, heart diseases, stroke, depression and Alzheimer.

What happens during sleep

Within the brain, sleep improves our ability to learn, memorise and make logical decisions and choices. By recalibrating our emotional brain circuits every night it keeps our mental health. By dreaming, it inspires our creativity and problem solving skills.

In the body, it restocks the cells of our immune system, regulates hormones related to blood sugar and appetite and helps to maintain a healthy microbiome in the gut. Sleep lowers the heart rate and blood pressure, maintaining the fitness of our hearts.

Even though sleep quantity is important (most people need an average of 7-9 hours of sleep per day), sleep quality is the key for optimal health. During the night, every approximately 90 minutes we go through different stages of sleep called REM and non-REM, which have different functions within the brain and body.

Missing some parts of these cycles means missing its benefits. For example, going to bed late decreases the amount of non-REM sleep, when the brain would be deleting all unnecessary information acquired through the day and storing the important ones (memory consolidation). By waking up too early, a big part of the REM sleep is missed, when dreams would be happening and problem solving and creativity skills improved.

Sleep hygiene

The human body follows a 24-hour “internal clock” called circadian rhythm, which is related to the sunlight. It’s programmed for us be fully awake during the day from the sunrise, and start to feel sleepy soon after dusk, when the natural sunlight fades and the temperature drops. This is when a substance called melatonin starts to be released.

These are some habits that can help you structure a healthy routine for a good night of sleep:

  • Avoid caffeine after noon
    As a stimulant, caffeine takes over 7 hours to be completely cleansed from the brain tissue. It competes in the brain with the substance responsible for building up the “sleep drive” over the day, called adenosine. Foods and drinks containing caffeine (such as coffee, black tea, green tea, dark chocolate and ice cream) should be avoided after 1pm.
  • Sunlight X darkness
    The stimulus from artificial lights, especially the blue light from screens, interferes with the release of melatonin, as it tricks our brains into believing that the sun has not set yet. It’s important to avoid screens for at least 2 hours before bed and also keep the bedroom as dark as possible through the night.
    On the other hand, starting the day with sun light exposure is a great way to shut down melatonin production and stimulate the production of cortisol, the hormone that drives us to be active.
  • Temperature
    To successfully initiate sleep our core temperature needs to decrease about 1°C.
    Keeping a cool bedroom temperature, having a bath before bed and selectively warming the feet and hands can help to initiate the sleep more easily.
  • Consistency
    Going to bed and waking up around the same time every day, including weekends, helps to regulate the circadian rhythm.
  • Regular exercise
    Regular exercise is an effective way to improve sleep quality. It helps to increase the non-REM sleep (restorative phase), decrease the sleep onset (how long we take to fall asleep – ideally it should be no longer than 20-30 minutes) and improves sleep duration. Aerobic exercises 3x/week outdoors, in the morning, are ideal to improve sleep quality.
  • Diet
    Ideally the last large meal should be at least 2-3 hours before bed time. Having a heavy meal before bed or going to bed hungry can affect the quality of sleep and hormone production.


Make the bedroom your sleep sanctuary. Wind down before bed by reading a relaxing book, practice meditation and breathing techniques, listen to calming music or give your self a massage with calming oils such as lavender.

A good night of sleep is the single most effective thing you can do to reset your brain and body each day and keep a strong immune system!