Exploring how what we eat — and when we eat — impacts our sleep and wellbeing
Quality sleep is essential for our overall health and wellbeing, yet many of us overlook its complexity and how deeply it connects to other aspects of our health—including our gut, and what and when we eat.
In episode four of Listen to Your Gut, our podcast exploring gut health, David Ray, Professor of Endocrinology at the University of Oxford and Co-Director of the Sir Jules Thorn Sleep and Circadian Neuroscience Institute, sheds light on the fascinating link between sleep and gut health. He explains how both are closely tied to our circadian rhythm — the body’s internal clock that regulates essential functions.
Also featured in the podcast is Jacquie Rees, who shares her personal journey of living with gastritis, from childhood illness to the ongoing impact on her sleep. She discusses how her condition has evolved over time, influenced by various health and lifestyle factors, including the crucial role of sleep.
So what do we need to know, and what can we do to improve our sleep and digestive health?
“We spend about a third of our lives asleep,” David explains in the podcast. “At its most fundamental level, sleep is a requirement to help repair the nerves in our brains that are busy during the day, and they need to recover during sleep. I think there’s a cost of being conscious, and the cost needs to be paid with some downtime when the nerves can repair themselves and get ready.”
But sleep is about more than just repairing tired neurons. It is deeply intertwined with our circadian rhythm, which governs countless biological processes.
How the circadian rhythm affects your body
Circadian rhythms are biological cycles synchronised with the 24-hour rotation of the Earth.
“All life on the planet — bacteria, plants, fungi, and animals — have evolved an internal timing system that allows them to anticipate the change from day to night and night to day,” explains David. “This drives behavioural changes, like when animals go out to look for food or find somewhere safe to sleep.”
Humans, however, are unique in their ability to disrupt these natural rhythms. With bright artificial lights, devices, and 24-hour work schedules, we’re increasingly altering our exposure to the natural light-dark cycle.
“Humans are the only animals that can alter their light cycle,” says David. “This is kind of an interesting experiment because it’s only really been possible in the last 50-100 years where light has become so cheap and so bright. There’s some horrifying data showing that even when you’re asleep, ambient light can increase your risk of developing diabetes.”
The gut: your second brain
The gut microbiome — home to trillions of microbes — is another critical player in this story. These microbes help with digestion, produce essential vitamins, and create molecules that regulate other parts of the body, including the brain.
“The microbiome is highly rhythmic,” David notes. “Its rhythmicity is driven by food timing. The microbes in the gut can’t see daylight, but they are subject to rhythmic arrival of food. In turn, they produce metabolites — small molecules that circulate in our blood and regulate organs like the liver and brain — at predictable circadian phases.”
Eating at irregular times or consuming food late at night disrupts this balance. “Digestion requires energy and neuronal activation, which stimulates the brain when it should be resting,” David explains. “Eating late at night or overnight, when your body expects to be in a fasted state, can lead to higher glucose levels, difficulty storing energy safely, and other metabolic issues.”
David’s tips for better sleep and gut health
So how can we optimise both our sleep and gut health? David offers practical advice:
- Follow a regular eating schedule
“It’s becoming clear that humans haven’t evolved to stay in a prolonged fed state. Eating a substantial breakfast after the overnight fast helps align metabolic clocks in the liver and gut with the brain’s circadian rhythm.” - Avoid heavy meals close to bedtime
“Eating near sleep can disturb sleep because digestion stimulates the brain,” says David. Give your body at least two to three hours after eating before you head to bed. - Get morning sunlight
Natural light helps synchronise your internal clock. “Even on a bright day, sitting near a window provides a thousand-fold less light exposure than stepping outside.” - Limit stimulants
Avoid caffeine for at least six hours before bedtime. David adds, “A warm milky drink before bed can be helpful. It’s not just the drink itself — it’s the habit of winding down that reinforces healthy sleep.” - Embrace downtime
Both the brain and the “second brain” in your gut need rest to function optimally. “What’s good for the brain in our head is also good for the brain in our gut.”
The bigger picture
As David eloquently puts it: “We’ve evolved to anticipate a significant fasted period. This steady state of nutrients during the rest phase allows the brain to focus on productive, restful, and recovery sleep.”
By aligning our eating habits and daily routines with our natural circadian rhythms, we can unlock better sleep, improved gut health, and overall wellbeing. It’s a reminder that sometimes, the key to health is simply allowing our bodies to do what they were designed to do.
EXPLORE OUR NEW PODCAST
Listen to Your Gut is a 10-part podcast series brought to you by ITN Business, with sponsorship from Yeo Valley Organic Kefir. This series delves into the intriguing world of the gut microbiome, featuring insights from individuals managing gut-related conditions and expert perspectives from academics, clinicians, and researchers. Together, we aim to shed light on the complexities of gut health.
Each episode focuses on a different aspect of gut health, aiming to increase awareness, debunk myths, share best practices, and amplify the voices of those living with gut-related challenges. Topics range from IBD, stress, and ADHD to sleep, diet, and the impact of our daily habits on our digestive health.
