Sleep as the Foundation of Health: How It Affects the Brain, Mood, Energy, and the Immune System

15.10.2025

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Sleep as the Foundation of Health: How It Affects the Brain, Mood, Energy, and the Immune System

Sleep is not just a time of rest – it is a key process during which essential functions take place to regenerate both body and mind. Quality sleep affects not only mood, energy, concentration, and overall mental well-being, but also the strength of the immune system. All of these can be supported through healthy habits and appropriate supplements. At the same time, avoiding behaviors that disrupt sleep can make regeneration as effective as possible.

What you will learn in this article:

Why sleep is important
How inadequate sleep affects health
The sleep cycle and its stages
What quality sleep should look like and tips to support it
Melatonin: more than just the “sleep hormone”
How to support sleep with supplements and natural remedies
When to seek professional help
Key takeaways

Why sleep is important

Sleep is essential not only for mental well-being and cognitive function but also for optimal immune system performance and physical recovery. Lack of sleep directly affects concentration, reaction speed, and decision-making, which significantly slows down. Even one sleepless night can reduce cognitive performance to a level comparable to mild intoxication. Being awake for 17–19 hours corresponds to the same decrease in reaction time as having a blood alcohol level of 0.5‰. This leads to slower responses, poorer judgment, and a higher risk of mistakes or accidents, especially when driving or performing tasks that require attention.

Regeneration: During deep sleep, muscles, tissues, and cells are repaired. Growth hormone is also produced, supporting recovery after physical exertion.
Immune system: Sleep stimulates the production of cytokines and white blood cells that protect the body against infections and inflammation. Insufficient sleep reduces resistance to illness and slows down healing.
Brain detoxification: A key component of sleep is the activation of the glymphatic system, which removes waste substances and accumulated metabolites from the brain. This process is crucial for long-term healthy cognitive function and the prevention of neurodegenerative diseases such as Alzheimer’s disease.
Hormones and metabolism: During sleep, levels of cortisol, insulin, and other hormones are regulated, supporting energy balance and helping to prevent chronic inflammation.
Mental well-being and mood: Quality sleep reduces stress, anxiety, and the risk of depression, which indirectly supports immune resilience as well.

Cognition and memory: Sleep enhances concentration and creativity. It also helps consolidate memories and supports long-term memory retention.

How inadequate sleep affects health

Lack of sleep doesn’t just cause tiredness – it has wide-ranging effects on health. Chronic sleep deprivation increases the risk of obesity, type 2 diabetes, high blood pressure, and cardiovascular diseases. Insufficient rest also weakens the immune system, making the body less capable of fighting infections and slowing down recovery. Finally, short or poor-quality sleep negatively affects mental health – it increases anxiety, contributes to depressive symptoms, and reduces resilience to stress.

The Sleep Cycle and Its Stages

Sleep consists of several stages that repeat in cycles approximately every 90 minutes. Each stage has a specific function and is essential for the regeneration of both body and brain. During sleep, it’s important to go through all stages so that all necessary bodily processes can take place. A lack of any sleep phase can lead to fatigue, reduced concentration, irritability, and weakened immunity.

NREM Sleep (Non-Rapid Eye Movement)

Stage 1 (light sleep): The transition between wakefulness and sleep. The brain slows down, muscles relax, and the eyes move slowly.
Stage 2 (deeper light sleep): Heart rate and body temperature decrease. The brain produces “sleep spindles,” which help stabilize memories.
Stage 3 (deep sleep): Also called delta sleep. The brain works slowly, while the body regenerates muscles, tissues, and cells. Growth hormone is released, and the immune system becomes active, clearing waste substances from the body.

REM Sleep (Rapid Eye Movement)

Occurs approximately 90 minutes after falling asleep and repeats several times during the night, with each cycle lasting longer than the previous one.
The brain is almost as active as during wakefulness, and the eyes move rapidly beneath closed eyelids. This is also the phase in which dreaming occurs.

REM sleep is essential for processing emotions, experiences, and consolidating long-term memory.

What Quality Sleep Should Look Like and Tips to Support It

Quality sleep is not only about the number of hours slept but also about depth, regularity, and rhythm. It should meet several basic criteria:

Sufficient duration and depth of sleep: For most adults, 7–9 hours of sleep per night is optimal. Shorter durations lead to insufficient recovery, while the need for extended “rest” often indicates poor sleep quality or another underlying health issue.
Regularity: Going to bed and waking up at approximately the same time each day helps synchronize your internal biological clock.
Continuity: Sleep should be smooth and uninterrupted, without frequent awakenings, allowing the body to pass through all sleep phases (NREM and REM).
Feeling refreshed in the morning and alert during the day: A sign of good-quality sleep is waking up feeling rested, maintaining stable energy throughout the day, and having good concentration.

To ensure high-quality sleep and all its benefits, we recommend:

- Proper circadian rhythm alignment: This can be supported by spending time outdoors in natural daylight during the first hour after waking, which delays melatonin (the sleep hormone) secretion. It is also beneficial to maintain regular wake-up and bedtime routines.

Limiting blue light before sleep: This type of short-wavelength light is emitted mainly by phone screens, computers, and LED lighting. In the evening, it suppresses the production of melatonin — the sleep hormone — which can disrupt falling asleep and reduce sleep quality. Therefore, we recommend avoiding blue light exposure at least one hour before bedtime. If screen time is unavoidable (for example, due to work), blue-light-blocking glasses or computer filters can help. Instead of regular LED bulbs, consider using special light sources that emit red light with an optimal wavelength.
We also recommend listening to the podcast with Hynek Medřický – The influence of light on the quality of our life.

Meditative rituals for calming the mind: If you have trouble falling asleep, incorporating evening meditation, breathing exercises, or other calming activities such as reading can help. Evening workouts should be of a gentler nature — yoga, stretching, or light walking are ideal. A warm bath or shower before bed can also promote relaxation.

Including physical activity in the morning or early afternoon: Exercise helps pleasantly tire the body and supports the natural circadian rhythm. Regular physical activity improves not only sleep quality but also overall mental well-being and stress resilience.

Light, protein-based dinner: Avoid eating large portions late in the evening — ideally, have your last meal at least two hours before bedtime. Dinner should also be easy to digest. This reduces digestive strain, promotes calmer sleep, and increases the likelihood of waking up refreshed.

Limiting caffeine and alcohol: We recommend avoiding large amounts of caffeinated drinks in the late afternoon and evening, as caffeine can interfere with sleep. Similarly, excessive alcohol consumption can have a negative effect on sleep quality.

Optimizing the bedroom environment: Focus on ensuring that your sleeping environment is quiet, dark, and slightly cooler than the rest of your home.

Herbal teas to promote sleep: Herbs provide a gentle and natural way to support a calm evening and quality rest. Drinking a warm tea before bedtime induces relaxation and helps the body transition into night mode. Try chamomile, lavender, or lemon balm infusions.

Melatonin: More Than Just the “Sleep Hormone”

Melatonin is a hormone produced in the pineal gland, primarily after dark, and regulates our circadian rhythm. Its release into the bloodstream triggers a feeling of sleepiness and helps facilitate the transition into sleep. It supports falling asleep, extends deep sleep, and improves sleep quality.

This hormone is also a powerful antioxidant that protects cells from oxidative stress, slows down aging processes, and supports brain and immune health. Its production and release are strongly influenced by light — morning sunlight suppresses its secretion, as does blue light from screens, while darkness stimulates its production.

Adequate melatonin levels not only promote better sleep but also enhance the body’s resistance to stress, infections, and premature cellular aging. As we age, melatonin production decreases, mainly due to changes in the pineal gland — its calcification and loss of active cells. This is why older adults often experience insomnia.

Consuming foods rich in protein, especially those high in the amino acid tryptophan (such as turkey, chicken, beef, oily wild fish, nuts, or seeds), supports melatonin production, as tryptophan serves as its precursor.

How to Support Sleep with Supplements and Natural Remedies

Magnesium: Magnesium in the form of magnesium bisglycinate promotes relaxation and calmness, which can help improve sleep onset and overall sleep quality.
Amino acid L-tryptophan: Serves as a precursor for the production of serotonin and melatonin. Supplementation may be beneficial, but we recommend focusing primarily on food sources.
Omega-3 fatty acids: Not only do they reduce inflammation and support brain function, but by improving cell membrane fluidity, they also facilitate serotonin transport to the brain — a precursor for melatonin production.
Melatonin: Suitable for disrupted sleep cycles or jet lag. However, we do not recommend taking it in large doses or for extended periods, as it can interfere with the body’s own melatonin production.

Adaptogens and herbal supplements:

- To support healthy sleep onset and a balanced circadian rhythm, ashwagandha can be helpful. It reduces cortisol and supports a regular sleep pattern. Herbs with mild sedative or hypnotic effects include valerian, chamomile, lavender, and lemon balm. These can be taken before bedtime as tea or tincture. You can also benefit from the calming effects of lavender by adding essential oil to a bath.

- Valerian root: One of the most effective herbs for sleep support. It acts directly on brain receptors that regulate nervous activity, shortening the time it takes to fall asleep and improving deep sleep quality. It is also used for anxiety and tension. Due to its strong aroma, tinctures or herbal extracts are preferred.
- Chamomile: Has a relaxing effect on the nervous system, relieves tension, and can ease mild digestive issues that sometimes interfere with sleep.
- Lavender: Calms the nervous system, reduces stress and anxiety, and promotes overall body relaxation.
- Lemon balm: Known for its calming properties, it helps with nervous tension and supports the body’s natural sleep rhythm.

When to Seek Professional Help

If sleep problems or insomnia persist for an extended period or significantly impact quality of life and work performance, it is important to consult a doctor or a specialist in sleep medicine.

Insomnia lasting longer than 3–4 weeks.
Severe fatigue, loss of motivation, irritability, poor concentration.
Possible treatment options include sleep hygiene, psychotherapy, or pharmacological support.
Insomnia and sleep disturbances may also occur as side effects of certain medications.

Key Takeaways

Sleep is essential for mood, energy, brain health, regeneration, and immunity.
Sleep quality can be improved through exposure to natural daylight, regular routines, evening hygiene habits, and physical activity.
Supplements such as magnesium, melatonin, adaptogens, omega-3s, and B vitamins can significantly enhance sleep quality.
It is important to avoid stimulants and stress in the evening.
If problems persist, seek professional help.