The Key to Life and Death
How bacteria influence our sleep
The human body needs to recover regularly during sleep. But sleep is much more than just relaxing the muscles, initiating regeneration processes and processing impressions in our dreams. It is an essential part of our lives and is influenced by our bacteria.
The little brother of death
Even in Greek mythology, sleep was referred to as the little brother of death. This was not intended to emphasize a danger, but rather its importance for the body. In mythology, Hypnos (the god of sleep) and Thanatos (the god of death) are brothers, both children of the night goddess Nyx. This connection led to the idea that sleep resembles death and is therefore like death’s “little brother”. However, this comparison is less about a possible “deadly” danger and more about the fact that both states represent a form of absence of consciousness or a different level of consciousness.
Plato described death as the final transition of the soul, while sleep was understood as a temporary loss of conscious being. Even though the Greek philosopher used this comparison to explain the immortality of the soul and the cycle of life and death, he emphasized the enormous importance of sleep for human beings. One possible interpretation according to Plato would be that people “test out” another world or level of consciousness during sleep without turning to it completely. This “test run” is an essential and necessary part of life.
Melatonin – the power hormone
Modern medicine, which is based on measurable values and studies, naturally sees things somewhat differently. Nevertheless, the enormous importance of sleep remains undisputed, without which no survival would be possible.
The hormone melatonin plays a key role here. It is a true “power hormone”, as it not only promotes sleep, but also general health. The hormone plays a central role in controlling the circadian rhythm in particular.
This internal clock is heavily dependent on melatonin. It controls many physiological processes in the body, such as sleep, wakefulness, hormone production and body temperature. The hormone is produced in the pineal gland, a tiny gland in the brain the size of a grain of rice. This in turn is controlled by the suprachiasmatic nucleus, a small region of the brain that is connected to the photoreceptors of the eyes. This compound prevents the pituitary gland from producing melatonin in daylight or blue light. In darkness, on the other hand, the pineal gland is signaled to produce melatonin, which triggers drowsiness.
How is melatonin produced?
This important hormone is produced from serotonin, and bacteria play a key role here. They support the production of serotonin. Although the serotonin produced by the bacteria in the intestine cannot pass the blood-brain barrier directly, its precursor, the amino acid tryptophan, can. The sequence is as follows:
- The gut microbiome influences the production of tryptophan.
- The tryptophan reaches the brain.
- Serotonin is produced in the brain.
- Serotonin is ultimately turned into melatonin in the brain.
The dual function of serotonin
In addition to its function as a precursor to melatonin, serotonin acts as a neurotransmitter in the brain and plays a central role in regulating mood. This is why it is often referred to as the “happiness hormone”. In the intestine, on the other hand, the serotonin produced by the bacteria supports digestion and influences blood pressure. Serotonin therefore has a dual function, depending on where it is formed or released.
The role of bacteria in sleep
Bacteria play a decisive role in processes that influence sleep. This illustrates once again that the microbiome should be understood as a part of the human being and not just as a collection of bacteria.
Firstly, the bacteria produce substances (short-chain fatty acids) that stimulate the human cells in the intestine to produce serotonin, which in turn can be converted into melatonin.
Secondly, bacteria influence the amount of tryptophan, from which serotonin and then melatonin are ultimately produced. Even if the bacteria themselves do not release tryptophan, they can cleverly modulate the amount of tryptophan produced in the intestine.
The melatonin in the intestine can reach the brain via the bloodstream. The blood-brain barrier, which protects the brain from many substances, can easily be penetrated by this small and fat-soluble substance, melatonin. In the brain, it then supplements the melatonin produced there by the pineal gland.
However, a large proportion of the melatonin produced in the intestine remains in the intestine and regulates digestion, protects the intestinal mucosa and supports the immune system. It also has an antioxidant and anti-inflammatory effect.
Studies thus show that both tryptophan produced in the gut, which is converted into serotonin and melatonin in the brain, and melatonin produced in the gut can be transported to the brain. However, the main melatonin production takes place in the brain through the pineal gland.
The biological rhythm is synchronized
Interestingly, gut bacteria have their own rhythm that is synchronized with the body’s circadian rhythm. If the biological rhythm is disturbed, for example by jet lag or shift work, the microbial populations in the gut can also become unbalanced, which in turn can affect sleep.
The connections between sleep and bacteria are complex and multifactorial – as is so often the case in the body, there is not just one single parameter that is decisive. Simplification can help to better understand the interactions, but should only ever be seen as such.
The gateway to sleep and death
But back to the pineal gland, which is often referred to as the gateway to sleep and also to death. Its main function is melatonin production, but it is also thought to be involved in regulating reproduction, influencing the immune system and even the ageing process.
It is one of the central switching points in our body, the guardian of sleep and reproduction and may play an important role in the dying process through the formation of DMT (dimethyltryptamine).
It is fascinating that this tiny gland in the brain can communicate directly and indirectly with bacteria.
Plato knew nothing about the existence of the pineal gland or bacteria. But he recognized more than 2,000 years ago that sleep and death are very similar.
The exact role of the pineal gland, particularly in death due to the possible increased production of DMT, is disputed in the scientific community. As is so often the case, different worlds collide here: the materialistic, measurement-based medical world and the philosophical world. Both are separated from each other, but there is a bridge that connects them.
Building bridges
This bridge may come as a surprise to many, but those who cross it open up a new dimension. This bridge is mindfulness.
Through mindfulness, insights can be gained that are excluded by the mind from the outset. It enables insights that cannot be achieved by purely evidence-based means. This is the strength of incorporating mindfulness into life.
And as we have seen, there is another world that plays a role in the overall system of life – sleep – death: the world of bacteria.
Because only when we connect all worlds with each other and do not exclude any of them do we have the opportunity to get to our origin and to understand ourselves. (JS)
_____________________
Further reading:
dos Santos, A.; Galiè, S. The Microbiota-Gut-Brain Axis in Metabolic Syndrome and Sleep Disorders: A Systematic Review. Nutrients 2024, 16, 390. https://doi.org/10.3390/nu16030390
Seong HJ, Baek Y, Lee S and Jin H-J (2024) Gut microbiome and metabolic pathways linked to sleep quality. Front. Microbiol . 15:1418773. https://doi: 10.3389/fmicb.2024.1418773
