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Sleep: Repair by Night, Performance by Day

Dr. Hüseyin Nazlıkul
Dr. Hüseyin Nazlıkul 20.05.2026 4 min read
Modern humans have come to underestimate sleep. "I sleep little but I manage." "Sleep is a waste of time…" Yet the body does not think this way.

Because sleep is not a passive process. Sleep is the time when the body is at its most active. And perhaps the clearest way to put it is this: a body that is not repaired at night cannot perform during the day.

Sleep: Not Shutting Down, But Opening Up

When we sleep, we do not simply close our eyes. In fact, the body opens up inward. During this process:

  • The brain clears out toxins
  • Hormones are balanced
  • Cells are renewed
  • The nervous system is reset

The reward for everything we do during the day is received at night. But modern life has disrupted this cycle.

Light, Screens, and the Disruption of the Biological Clock

The human body operates according to light.

  • daylight → activation
  • darkness → rest

But today:

  • Screen light at night
  • Artificial lighting
  • Irregular living hours

suppress melatonin production. Melatonin is not just the “sleep hormone.”
It is also:

  • A powerful antioxidant
  • An immune regulator
  • A cellular protector

When melatonin is disrupted:

  • Sleep becomes shallow
  • Repair decreases
  • Aging accelerates

The Autonomic Nervous System and Sleep

Sleep is the most important regulatory domain of the autonomic nervous system.

During deep sleep:

  • The parasympathetic system becomes dominant
  • Heart rhythm slows
  • Breathing deepens
  • Muscles relax

During this process, the body: shifts into “repair mode.” But a person living under stress:

  • Cannot fall asleep
  • Wakes frequently at night
  • Gets up tired in the morning

Because the nervous system is still in “alarm mode.”

Sleep and the ECM: Nighttime Cleansing

The ECM (extracellular matrix) is cleansed most actively at night. During sleep:

  • Microcirculation increases
  • Toxins are cleared away
  • Cellular communication is regulated

But sleep deprivation causes:

  • A buildup of load in the ECM
  • Increased inflammation
  • Disrupted cellular communication

For this reason: sleep is a cleansing process not just for the brain, but for the entire body.

Cleansing the Brain: The Glymphatic System

A system discovered in recent years: the glymphatic system.

This system:

  • Clears waste between brain cells
  • Removes toxic proteins
  • Provides protection against neurodegenerative diseases

But this system only operates during deep sleep. In other words, a brain that cannot sleep cannot be cleansed.

The Gut and Sleep: A Silent Relationship

There is a strong connection between the gut and sleep. The gut flora:

  • Affects melatonin production
  • Maintains serotonin balance
  • Regulates inflammation

When the gut is disrupted:

  • Sleep quality declines
  • Nighttime awakenings increase
  • Morning fatigue occurs

For this reason: sleep problems often begin in the gut.

Late-Night Meals: A Silent Sabotage

Eating late at night:

  • Raises insulin
  • Suppresses melatonin production
  • Strains digestion

While the body wants to carry out repair at night, it is forced to deal with digestion instead. This results in:

  • Poor-quality sleep
  • Morning fatigue
  • Metabolic disturbance

as a consequence.

Intermittent Fasting and Sleep

Intermittent fasting directly affects sleep quality. An early evening meal:

  • Supports melatonin production
  • Eases digestion
  • Facilitates the transition into deep sleep

For this reason: sleep is not independent of nutrition.

Sexuality and Sleep

Healthy sexuality:

  • Increases oxytocin release
  • Reduces stress hormones
  • Activates the parasympathetic system

This, in turn, eases the transition into sleep. In other words, sleep is not only a biological process, but an emotional one as well.

Breathing: The Door That Opens Into Sleep

A person who breathes shallowly has difficulty falling asleep. Deep, rhythmic breathing:

  • Activates the vagus nerve
  • Regulates heart rhythm
  • Calms the mind

For this reason, breathing exercises before sleep are one of the most natural “medicines” there are.

Longevity: Those Who Can Sleep, Live

One of the most important determinants of a long life is: sleep quality.

A person who sleeps well: gets sick less often, recovers faster, lives longer.

But when sleep is disrupted: immunity weakens, inflammation increases, aging accelerates.

The Greatest Problem of Modern Humans: Forgetting How to Sleep

Humans learned to work, learned to succeed, learned to move faster… But forgot how to rest.

Yet nature teaches us this:

  • Movement by day
  • Rest by night

When this cycle is disrupted, humans become disconnected from nature.

A Final Word: Respect for the Night

Night is not merely darkness. Night is the time when the body finds itself. Sleep is not an obligation, but an opportunity—an opportunity to meet yourself, to listen to your body, to begin again…

And finally:

Sleep is not a luxury.
Sleep is the foundation of life.
A body that is not repaired at night
cannot live during the day.

For more information on this and similar topics, you can refer to my books “Regulated Life, Longevity” and “I Can’t Sleep.”

You can learn more about neural therapy and Hüseyin Nazlıkul’s other treatment methods here.

Here; /icerik/noralterapi-tedavisi-213

Hüseyin Nazlıkul