How Digestion and Sleep Work Together

“Rest, digest” is a popular phrase in wellness circles, but the reverse – “digest, rest” – is also important.  You may have noticed that your appetite, digestion and gut health can feel different when you are tired, or that heavy meals make you feel tired.  Here we take a look at how sleep and digestion are connected, and what you can do to support both, and feel healthier.

This phrase is often used to highlight the importance of sitting down, distraction free, to relax while eating meals.  Daily stresses can slow digestion, reduce appetite as our stomachs feel like they’re ‘in knots’, and give us an uncomfortable bloated feeling after the meal.  But, our main resting process of sleep also plays a role through the circadian rhythm.

You’re probably familiar with the phrase, but just in case: circadian rhythm is essentially the body clock.  It’s what wakes you in a morning at a regular time even if your alarm didn’t go off, and it makes you feel sleepy at your regular bedtime.  The circadian rhythm also impacts our gut – how it works and our appetite.  More specifically, circadian rhythm can affect:

• The times of day that you feel hungry.
• How the digestive system functions, for example: movement, the release of enzyme and digestive juices and absorption of nutrients.
• Hormone balance.

The circadian rhythm works on a 24-hour cycle, and is mainly influenced by light, but our habits – dietary and lifestyle – can influence it.  Changes in our habits can disrupt the rhythm.

Shift work, particularly night work, and international travel have been shown in studies to negatively impact our circadian rhythm as we are forced to ignore the natural cues, such as changes in natural light, and follow irregular eating patterns.

The disruption of your circadian rhythm, and inadequate sleep, may result in digestive issues such as:

• Increased risk of inflammatory bowel disease (IBD).
• Increased risk of irritable bowel syndrome (IBS).
• Increased risk of stomach ulcers.
• Increased cravings for high-calorie, sugary foods.

Scientists believe that our sleep patterns not only affect the health of the gut structure, but also the microbiome that can influence our general health including our immunity and weight management.

Digestion does not stop when we sleep, although it does slow down as the body moves to a rest and repair state.  This slowing means that it takes longer to move food through your body, potentially contributing to symptoms such as reflux and nausea.  Of course, when we go to bed we typically lie down, which also increases the risks.  Not only can reflux feel uncomfortable, it can contribute to symptoms such as hoarseness, laryngitis, coughs, asthma and bronchitis.  There is also a two-way link between reflux and snoring, with each having the potential to aggravate the other.  While prevention is best, if you do experience discomfort from reflux during the night, try sleeping on your left side as this puts the upper stomach opening in an upwards position.  If you have persistent problems with reflux at night, consult your GP.

Eating late may also result in increased blood sugars as our sensitivity to insulin naturally reduces at night, meaning that less sugar is moved into storage*.  This can disrupt sleep not only due to the sugar-spike (and the later sugar crash), but also because high levels of blood sugar can increase our stress hormones too.  Some studies suggest that it may also result in the retention of sodium, which can increase fluid retention and swelling of the mucous membranes contributing to nasal congestion and early waking.  Furthermore, if you sleep on your back you may increase your risk of fluids around your airway, increasing your risk of broken sleep and sleep apnoea.

*If you are living with diabetes, it is important that you continue to follow advice from your medical team regarding blood sugar management.  Any changes to your diet should be discussed with them in the first instance to protect your health.

While we discussed the circadian rhythm above with regards to sleep, eating at irregular times can also disturb your circadian rhythm.  However, it’s not just the timing of food that can disturb our sleep, it is also the content.  Spicy food, stimulants (e.g. caffeine and sugar) and low quality food (e.g. ultra-processed foods) can also be a problem for some people.

Eating according to your body clock is referred to as chrononutrition.  But, I’m not going to go into the technical aspects of this, instead here are some simple suggestions to help you keep this two-way relationship healthy:

• Avoid eating large meals less than two hours before bedtime.
• Consider eating larger meals during the earlier parts of the day, if practical.
• Eat a diet rich in a variety of whole nutrient-dense foods (especially plant-sourced foods) to support your gut health, hormone production and circadian rhythm – think vegetables, whole grains, protein and fruit (up to two portions per day).
• If you feel that you need to snack after your evening meal choose nutrient-dense foods such as veg sticks with houmous, or apple slices with nut butter.
• Eat at consistent times each day.
• Avoid caffeine after mid-afternoon (earlier if you are sensitive to it).
• Go to bed and get up at a consistent time each day – that includes the weekends!
• Aim for 7-9 hours sleep per night.
• Spend time outside in daylight each day to help your body recognise day/night cycles.
• If you smoke or vape, stop. Nicotine is a stimulant that affects the gut’s nervous system.  It can negatively affect sleep, contribute to digestive problems, and may increase stomach acid and aggravate problems with reflux.

If you work shifts or travel abroad frequently:

• Try spending time in bright light during your working hours and darken your environment when you are preparing for sleep (use sunglasses, if safe, to travel home after a night-shift; use blackout curtains and eye mask for daytime sleep).
• Try blue-light blocking options on screens when preparing to sleep.
• Avoid large meals when working the night-shift part of your rota, focusing instead on lighter, nutrient-dense meals that include protein and vegetables.
• Avoid caffeine during the second half of a night-shift to support sleep when you have finished.
• Exercise (engage in physical activity) during your waking hours each day, rather than aiming for a fixed time.

While the two processes may appear unrelated, our digestion and sleep are interconnected.  This means that making changes to support one process may help the other.  Remember that it isn’t always necessary to make big changes suddenly – choose one of the tips above to implement daily for a few weeks before adding a further change.  If you need to adjust the time that you eat your evening meal but the idea of eating 2 hours earlier feels like chaos, trying shifting it in 15 or 30 minute increments over the course of a few weeks to lessen the impact on your daily planning.

• Circadian rhythms: a regulator of gastrointestinal health and dysfunction – Voigt, Forsyth and Keshavarzian (2019)
• The Future of Shift Work: Circadian Biology Meets Personalised Medicine and Behavioural Science – Potter and Wood (2020)
• Sleep disorders related to nutrition and digestive diseases: a neglected clinical condition – Vernia, et al (2021)
• Late-Night Feeding, Sleep Disturbance, and Nocturnal Congestion Mediated by Hyperglycemia, Renal Sodium Retention, and Cortisol: A Narrative Review – Brown (2025)