The optimal sleep

Many associate summer with recovery, yet the season often introduces specific challenges for the body. Bright nights, higher temperatures, and altered habits, such as dietary changes and a potentially increased alcohol intake, can subtly disrupt the biological clock. Recent scientific advances demonstrate connections that extend far beyond a temporary feeling of fatigue. They significantly influence the composition and function of the gut microbiota.

The microorganisms in the gut maintain a continuous dialogue with the central nervous system via the gut-brain axis. This mechanism implies that a disrupted circadian rhythm quickly manifests in gastrointestinal health. While an imbalanced gut microbiota can impair sleep quality and initiate a negative spiral (Lin et al., 2024).

 

The circadian rhythm and the internal clock of the gut microbiota

The sleep cycle is regulated by biological rhythms, and studies show that the microorganisms in the gut possess their own circadian rhythm. In fact, a significant portion of the human gut microbiota composition follows a strict rhythm throughout the 24-hour cycle.

When the circadian rhythm or sleep patterns are disrupted—for instance, by bright summer nights or irregular sleep schedules, a measurable alteration occurs among the bacteria in the gut (Lin et al., 2024). Scientific data indicate that these shifts can lead to:

• An alteration in the balance between the bacteria in the gut microbiota, which is frequently linked to adverse effects on metabolism (Lin et al., 2024).
• A reduction in beneficial and indigenous bacterial strains, such as Lactobacillus (Lin et al., 2024).
• A decrease in microbial richness and bacterial diversity, which weakens the natural protective barrier of the gut (Lin et al., 2024).

When sleep patterns return to a regular schedule, the balance generally stabilizes, underscoring the importance of consistent sleep routines.

 

Summer lifestyle factors

In addition to light and heat, the summer months tend to involve dietary changes and, for some, a more frequent intake of alcohol, which affects the body’s capacity for recovery on multiple levels.

Alcohol, REM sleep, and respiratory pauses

Alcohol initially exerts a relaxing effect and can shorten the time it takes to fall asleep (Gardiner et al., 2025; Ebrahim et al., 2013). However, research shows that alcohol impairs sleep quality in several ways. Among other effects, it disrupts REM sleep (dream sleep), which is essential for mental health and emotional balance (Gardiner et al., 2025; Ebrahim et al., 2013).

As blood alcohol levels decline, the body responds by increasing the secretion of stress hormones, leading to fragmented sleep characterized by frequent awakenings. Furthermore, alcohol acts as a muscle relaxant on the tissues of the throat. This increases the risk of snoring and airway obstructions during sleep, known as sleep apnea.

These respiratory pauses lower oxygen saturation and force the body and brain to wake up briefly. Within gut microbiota research, sleep apnea has been observed to reduce microbial diversity and increase the abundance of bacteria capable of driving inflammation and compromising the gut barrier (Lin et al., 2024).

Neurotransmitters and inflammation

A substantial portion of the body’s chemical signaling system originates in the gastrointestinal tract. For instance, over 90% of the body’s serotonin is synthesized in the gut. Serotonin constitutes the essential building block required for the production of the sleep hormone melatonin. Certain specific gut bacteria assist in stimulating this process.

Current research highlights that when heavy food is consumed late or when alcohol is ingested, the production of short-chain fatty acids—which gut bacteria generate when fermenting dietary fibers, decreases. These fatty acids are necessary to suppress inflammation. When the production of these substances declines, it can lead to increased systemic inflammation, which in turn has been shown to disrupt sleep and exacerbate feelings of exhaustion.

 

Targeted interventions for improved sleep

Research indicates that it is possible to break this negative spiral through the targeted administration of bacteria and fibers. Specific interventions have demonstrated substantial potential in correcting imbalances in the gut microbiota and thereby improving sleep quality.

• Probiotics – Specific strains of Bifidobacterium and Lactobacillus.
• Prebiotics – Specific dietary fibers.

These components influence several central pathways in the body. For example, they attenuate inflammation that would otherwise disturb nocturnal sleep and contribute to stabilizing the natural circadian rhythm (Lin et al., 2024). Administering a combination of these components (synbiotics) provides the gut microbiota with the necessary tools to support sleep from within.

 

Advice for a balanced sleep

To optimize the conditions for high sleep quality and maintain a stable gut microbiota during the summer, the following concrete strategies can be applied:

• Regular light exposure – Early exposure to natural daylight stabilizes the production of sleep hormones later in the evening, which helps keep both the biological clock and the balance of the gut microbiota aligned (Matenchuk et al., 2020).
• Temperature regulation – Keeping the bedroom cool facilitates the natural core temperature drop required for the night, making it easier to fall asleep and reducing the risk of nocturnal awakenings (Thompson et al., 2017).
• Prebiotic foods – Increasing the intake of dietary fibers found in foods such as asparagus and onions nourishes beneficial gut bacteria. This enhances the production of protective short-chain fatty acids and counteracts stress-induced inflammation (Lin et al., 2024).
• Avoid late food intake – Avoiding heavy meals and alcohol during the final hours before bedtime reduces gastrointestinal workload. This preserves REM sleep and protects the intestinal mucosa (Gardiner et al., 2025; Lin et al., 2024).
• Synbiotic supplementation – Introducing a high-quality synbiotic supplement ensures a concentrated and synergistic combination of live bacterial strains and prebiotic fibers. This administration supports a balanced gut microbiota and counteracts the dysbiosis that can arise from altered summer habits.

Purchase Synbiotic here

By combining a conscious circadian rhythm with a diet and lifestyle that support gastrointestinal health, the optimal prerequisites for deep and restorative sleep are established (Lin et al., 2024).

 

References

Lin, Z., Jiang, T., Chen, M., Ji, X., & Wang, Y. (2024). Gut microbiota and sleep: Interaction mechanisms and therapeutic prospects. Open Life Sciences, 19, 20220910. https://doi.org/10.1515/biol-2022-0910

Gardiner, C., et al. (2025). The effect of alcohol on subsequent sleep in healthy adults: A systematic review and meta-analysis. Sleep Medicine Reviews, 80, 102030.

Thompson, R. S., et al. (2017). Dietary Prebiotics and Bioactive Milk Fractions Improve NREM Sleep, Enhance REM Sleep Rebound and Attenuate the Stress-Induced Decrease in Diurnal Temperature and Gut Microbial Alpha Diversity. Frontiers in Behavioral Neuroscience, 10(240). https://doi.org/10.3389/fnbeh.2016.00240

Ebrahim, I. O., Shapiro, C. M., Williams, A. J., & Fenwick, P. B. (2013). Alcohol and sleep I: effects on normal sleep. Alcoholism: Clinical and Experimental Research, 37(4), 539–549.

Matenchuk, B. A., Mandhane, P. J., & Kozyrskyj, A. L. (2020). Sleep, circadian rhythm, and gut microbiota. Sleep Medicine Reviews, 53, 101340.