III.8

Sleep and circadian rhythm

Sleep is not wasted time but active healing. Your gut flora has a daily rhythm of its own, and when you sleep well, the engrafting bacteria find better conditions too. This chapter shows you how to set your own body clock.

Összefoglaló

It is easy to think of sleep as simply "switching off", but the reality is the exact opposite: during sleep your body is at its most active when it comes to repair and recovery. Your gut flora — including the freshly transplanted bacteria now engrafting — also lives by a daily rhythm: it behaves differently by day than by night. If your own daily rhythm is predictable and restful, you create the background conditions for the new flora to feel at home and take root. This chapter is not about sleeping pills but about simple, adjustable habits: light, dark, consistent timing and a few evening routines that set your body's internal clock alongside your healing.

The internal clock — and why your gut flora cares

Almost every organ in your body works to a shared, roughly 24-hour rhythm — this is what we call the circadian rhythm^[G]. It governs when you are alert and when you are sleepy, when your body temperature rises and falls, and even the pace of your digestion. The internal clock is set chiefly by light: morning brightness tells your body "it's daytime", and evening darkness tells it "it's time to rest".

The surprising part is that your gut bacteria have a daily rhythm of their own too. By day, when you eat and move, they behave differently than by night, when your gut is at rest and clearing out. When your own rhythm is steady — going to bed and getting up at roughly the same time — you keep your flora's rhythm in order as well. Irregular sleep, late-night eating or a reversed day-night cycle disturb exactly this delicate harmony.

During the engraftment phase, sleep is therefore doubly useful. On the one hand, you yourself recover better, are less tired and less irritable, which you also need in order to see the course through. On the other, a predictable rhythm creates a favourable, stable environment for the engrafting flora too.

The building blocks of good sleep

Good sleep is not a matter of luck but the result of a few habits. The most important is consistency: try to go to bed at roughly the same time and — more importantly — to get up at the same time, even at the weekend. Your wake-up time anchors your internal clock; if it is steady, falling asleep becomes easier too.

Light is your most powerful tool. In the morning, as soon as possible after waking, let in natural light — draw the curtains, or step outside for a few minutes. In the evening, by contrast, dim the lights, and in the final hour avoid the strong blue light of phones and screens, because this holds back the production of melatonin^[G] — the "falling-asleep hormone". Keep the bedroom dark, quiet and rather cool.

A few practical tricks help a great deal: it is worth giving up caffeine after two in the afternoon, because it lingers in your body for hours; avoid heavy, late-evening meals, because a full stomach worsens sleep quality; and alcohol — although it makes you drowsy — fragments night-time sleep and makes it shallow, and is in any case to be avoided during the course. A calm evening routine — a warm shower, reading, a few minutes of slow breathing — signals to your body that rest is approaching.

Light as the strongest lever of your body clock

Light is worth highlighting separately, because it is the lever with which you can do the most for your internal clock — and most people use it the wrong way round. The circadian rhythm is held together by the alternation of light and dark: your eyes are not only for seeing, but as light sensors they also signal to your body that it is "daytime" or "night-time".

Morning light is the most important dose. As soon as possible after waking, get into strong, natural light — draw the curtains, stand by the window, or step outside for a few minutes, even in overcast weather (outdoors, even an overcast sky is many times brighter than indoor lighting). This morning light dose sets the daily clock, sharpens alertness, and — because it also brings forward the timing of melatonin — makes falling asleep easier in the evening. If you can, pair it with a morning walk or with your coffee beside a window.

In the evening the goal is the reverse: less light and warmer light. After sunset, dim the lamps, and in the final hour or two avoid the strong, blue-toned light of phones, tablets and television, because this type of light brakes melatonin production and "lies daytime" to your body. If you do use a screen, switch on the evening/warm colour mode and turn the brightness down. Morning brightness and evening darkness together — not separately — produce a stable rhythm.

When sleep just won't come

It is entirely normal for sleep to stutter at times during illness and treatment — the symptoms, the worry, or getting up for the toilet at night can all disrupt it. Do not make more of it than it is: the more anxious you are about sleep, the harder it becomes to fall asleep.

If you toss and turn for more than twenty minutes, do not stay in bed tense. Get up, go into another, dimly lit room, do something dull and soothing (read a few pages), and only lie back down when you feel sleepy again. This way you preserve the link between bed and sleep. Avoid short daytime naps — especially in the late afternoon — because they take away your evening sleepiness.

Important: use sleep aids or supplements (including melatonin) only in consultation with your treating physician during the course. If the sleep disturbance is persistent and seriously affects your daily life, that too is a subject for a medical conversation — you do not have to struggle with it alone.

🍽️ Eating during these days

The theme of this week is sleep and circadian rhythm, and although the three days are primarily about sleep hygiene (fixed wake-up and morning light — day 46; evening winding-down, a screen-free final hour — day 47; bedroom and difficult nights — day 48), eating has a concrete task here too: avoiding a heavy, late dinner and having dinner at least 2–3 hours before bed, as well as giving up caffeine after 2 p.m. — these all support sleep quality and the natural rise of melatonin.

For these days, the Plant Calendar (Appendix F) recommends olives (day 46), extra-virgin olive oil (day 47) and green tea / matcha (day 48) — three polyphenol-rich sources. These days fall into the calendar's "gradual expansion" (days 31–50) phase, where the aim is to gradually increase plant diversity and polyphenol sources. On reaching the colon, polyphenols become food for the good bacteria, support a diverse flora, and also have an anti-inflammatory effect — so alongside increasing diversity, they also help to calm post-infection inflammation. Green tea additionally counts towards your fluid intake; just take care, because of its caffeine content, not to drink it in the late afternoon or evening, so that it does not disturb your sleep.

🩺 Klinikai blokk

The central clock of the circadian rhythm sits in the suprachiasmatic nucleus (SCN) of the hypothalamus, set by light sensing in the retina; the peripheral clocks — including the gut epithelium's and the microbiota's own oscillators — synchronise to it. The gut microbiota shows daily compositional and functional fluctuation (diurnal oscillation); circadian disruption of the host (jet lag, shift work) is accompanied by a shift in the microbiota's rhythm and by dysbiosis (after Thaiss and colleagues 2014 [59]). Melatonin, a product of the pineal gland, is darkness-dependent and is also present in the GI tract, where it modulates motility and the mucosal barrier.

Sleep deprivation can result in a pro-inflammatory state and raised evening cortisol^[G], which can impair gut barrier function and the conditions for engraftment. During the engraftment phase, a stable sleep-wake cycle is therefore not merely symptomatic comfort but a supporting factor in flora stabilisation. From a clinical standpoint, melatonin or sedative supplementation during the course is to be avoided without individual medical judgement; chronic insomnia and a disrupted circadian rhythm worsen the quality of life of CDI patients, which is why sleep-hygiene intervention is an integral part of the lifestyle pillar of the Patient Recommendation.

Day 46 – Anchoring your wake-up

Today you fix your wake-up time and let in light in the morning — these two steps are the foundation of your internal clock. A consistent wake-up is worth more than a perfect bedtime.

Set a fixed wake-up time and keep it at the weekend too (±30 minutes)
Within 10–15 minutes of waking, let in natural light or step outside for a few minutes
Light reminder: strong, natural morning light is your most powerful lever — even in overcast weather, outdoors your eyes receive the most light
Drink your morning coffee, but give up caffeine after 2 p.m.
Diary: bedtime and wake-up time, hours of sleep, how you feel

Day 47 – Winding down in the evening

Today you focus on the evening hours: dimmed light, a screen-free final hour and a soothing routine. This helps the natural rise of melatonin.

In the final hour, dim the lights and put down the phone/screen
Have dinner at least 2–3 hours before bed; avoid heavy, late eating
Introduce a short evening routine: a warm shower, a few pages of reading or slow breathing
Diary: hours of sleep, ease of falling asleep, night-time awakenings

Day 48 – The bedroom and handling challenges

Today you set up the environment and how to handle difficult nights. The goal is for the bed to remain the place of sleep.

Make the bedroom dark, quiet and cool (blackout, quiet, ~18–20 °C)
If you don't fall asleep within 20 minutes, get up, do something dull in dim light, and only lie back down when sleepy
Avoid late-afternoon naps
Use a sleep aid (including melatonin) only in consultation with your doctor
Oral hygiene: keep twice-daily brushing and interdental cleaning — the mouth is part of the microbiome too, and bacteria can reach the gut from the mouth

🍽️ Eating during these days

📊 Adat

During the sleep phase, record daily:

sleep: bedtime and wake-up time, hours of sleep;
ease of falling asleep and number of night-time awakenings;
how you feel (1–5) and mood;
fluid intake (litres);
daily stool count and Bristol scale — core CDI data;
DiffBiome dose (capsules/day) and LOT number.
Movement: type + minutes, step count (target/actual)
Stress level (1–5) and mood (1–5)

Why does this matter?

Sleep is active healing: this is when you recover, and a stable daily rhythm also creates a favourable environment for the engrafting gut flora. You don't need sleeping pills but a few adjustable habits — a fixed wake-up, morning light, evening winding-down — that set your body's internal clock alongside your healing.

[[REFERENCES]]

References

[59] Thaiss CA, Zeevi D, Levy M et al. Transkingdom control of microbiota diurnal oscillations promotes metabolic homeostasis. Cell. 2014. Link

Mechanistic study in mice and humans demonstrating that the gut microbiota exhibits diurnal oscillations driven by feeding rhythms, producing time-specific compositional and functional profiles. Disruption of host molecular clock components or jet lag caused aberrant microbiota oscillations and dysbiosis through impaired feeding rhythmicity. Jet-lag-induced dysbiosis in both species promoted glucose intolerance and obesity that were transferable by FMT to germ-free recipients. Identifies microbiota–host circadian cross-regulation as a metabolic disease mechanism.