Sleep & Gut Health

Everyone sleeps. In fact, the average person spends a third of their life sleeping. However, the amount of sleep we get and the quality of it have a huge impact on our health. In addition, research shows that our gut microbiome is also deeply connected to sleep. So why is sleep important? And how is it connected to your gut microbiome?

The importance of sleep

Sleep is crucial for both mental and physical recovery. It affects everything from energy levels, mood, hormone production, immune system and digestive system. For example, sleep deprivation can lead to increased hunger and appetite. This is due to altered levels of certain hormones that regulate appetite: higher levels of ghrelin and lower levels of leptin.

Too little sleep, waking up during the night, or sleep problems affect the quality and quantity of sleep. This affects the quality of life and can lead to long-term consequences for your health, such as type 2 diabetes, cardiovascular disease, obesity, and depression.

Circadian rhythm

The circadian rhythm is the 24-hour biological clock in the body. It is the phenomenon that regulates the wake-sleep phases. This rhythm causes changes in the body in response to external signals, such as light, to prepare the body for expected changes (e.g. sleep or waking).

Disruption of the circadian rhythm sleep phase, for example through night work, night flights or jet lag, affects healthy sleep patterns. In addition, exposure to blue light from electronics in the evening/night has been shown to downregulate the production of melatonin, a hormone that regulates the sleep-wake cycle and alters the circadian rhythm.

In the long term, this can lead to sleep disorders and chronic health problems, as well as disrupting the gut microbiome.

Can sleep affect your gut health?

The gut and brain constantly communicate through a two-way axis: the gut-brain axis. They interact via, among other things, nerve cells, microbes, microbial metabolites, and short-chain fatty acids (SCFAs).

Poor quality sleep and disrupted circadian rhythms affect the microbiome through this gut-brain axis communication. This is associated with gut dysbiosis (an imbalance between beneficial and non-beneficial bacteria), with lower levels of the beneficial species: e.g. Lactobacillaceae and Bifidobacteriaceae , and higher levels of the non-beneficial bacteria: e.g. Ruminococcus gnavus .

But can your gut health also affect your sleep?

It is not yet conclusively proven whether the composition of the gut microbiome can affect your sleep. A bidirectional or cyclical relationship has been suggested, meaning that the sleep we get affects the microbiome, and vice versa.

It has been proven that the microbiome can lead to alternative sleep patterns through gut-brain axis communication. Overall, increased microbiome diversity, with higher numbers of beneficial bacteria, is positively associated with sleep quality and quantity.

In addition, 90% of the hormone serotonin is produced by gut bacteria. Serotonin is a precursor to melatonin (the sleep hormone). Higher concentrations of melatonin are associated with more serotonin-producing bacteria in the gut, which have been shown to positively affect sleep and circadian rhythms.

How to improve sleep quality?

Sleep is something we can directly control. We should therefore strive to get enough sleep and optimize its quality. This will positively affect our gut microbiome and our overall health.

• Try to get 7-9 hours of sleep every night.
• Try to go to bed around the same time every day, as it helps set your body's internal clock and optimize sleep quality.
• Optimize your sleep environment by ensuring proper lighting, a comfortable temperature, and getting fresh air into the room.
• Avoid exposure to blue light from electronics within 1-2 hours before your bedtime.
• Avoid caffeine late in the day and large meals before bed.
• Get enough daily exercise and movement.
• Spend time outdoors when it's light to increase your alertness.

Key messages

• Getting enough, good-quality sleep is essential for optimal health.
• Sleep and the gut microbiome are deeply connected: Disrupted sleep and circadian rhythms negatively affect the gut microbiome. Conversely, it appears that a healthy gut microbiome can improve sleep quality.
• We should therefore strive to improve our sleep to positively impact our gut microbiome and overall health.

Author:  Ingeborg Amble Holtmann