Inulin for Sleep: Does It Really Help?

Inulin for Sleep: Does It Really Help?

It’s been picking up traction in the news – how you treat your digestive system can affect how well you sleep at night. The systems behind this are much more complex than they seem, and can have surprising knock-on effects around the body. We’re going to focus on one supplement for the gut that can play a part in this: inulin.

This article is going to look into how inulin can help you get a good night’s sleep. It might not seem like the most direct way, but the science behind the process may surprise you.

What is Inulin?

Inulin is a sweet, starchy powder that’s made by plants and used as an energy source. It’s found in large amounts in bananas, asparagus, leeks and chicory, where the supplement industry sources its inulin. It’s part of a group of carbohydrate chains called fructans, which are usually found in certain vegetables, but especially in onions, broccoli and the foods listed earlier. The human body finds it difficult to digest fructans like inulin, and that’s why it works as an effective supplement.

When you eat inulin, it survives the harsh conditions of the stomach and small intestines intact, passing through to the large intestines. When there, it’s used as sustenance for the bacteria that live in the lower gut, replenishing them. This kind of substance is called a prebiotic; which is different but related to the probiotics that deliver ‘good bacteria’ to your gut via foods and supplements. Prebiotics essentially act as a kind of fertiliser for probiotics, helping them grow, divide and live longer inside you.

Naturally, prebiotics have a number of obvious benefits to your digestion, but they can also have positive effects all around the body. We’re still learning about the extent to which gut bacteria affects the rest of the body, and we’re still being surprised about what we’re discovering. One such surprising discovery is how your gut microbiota can influence your sleep.

Prebiotics and Sleep

With two thirds of people in the UK having disrupted sleep (according to a 2017 survey) many of us are looking for any way we can to get rest. Whilst not intuitive, the conditions inside your gut may play a part.

The kernel of this theory comes from a 2017 study, where the theory that prebiotics could assist in sleep was tested in rats. They were given a dairy-based prebiotic diet and placed under certain conditions to test their reactions. From the multiple conclusions drawn, there are two very interesting ones.

Firstly, the subjects had “improved NREM sleep consolidation”. This means they spent more time asleep compared to before, but in a particular state of sleep. Non-rapid eye movement (NREM) sleep is what makes up about 80% of the time we spend asleep; where our muscles twitch and our breathing and heart rate gradually slows. We don’t spend this part of sleep dreaming, but it’s important in another way: a lot of the restorative effects of sleep happen during this state, such as repairing damaged tissue and growing new muscle and bone.

The second important conclusion is that the prebiotic diet “support[ed] beneficial REM sleep rebound following acute stress”. Rapid Eye Movement (REM) sleep is the stage where deep sleep occurs and vivid dreaming happen. It’s been link to memory and learning, and a lack of REM sleep can disrupt these processes.

As mentioned, this experiment was conducted on rats, but since then there have been observations of prebiotics helping sleep in humans. In May 2017, a BBC documentary looking into sleep and insomnia tested prebiotics, taking them for five days and measuring how much time spent in bed was spent awake. That time dropped from 21% at the start of the experiment, to 9% at the end. Although, this experiment may not be the most scientifically sound, having no official write up and being used for television.

Another, more official review on the subject, states that understanding of the microbes in the gut may lead to better treatments of sleep disorders in the future, but that evidence is “still scarce”.

Let’s go back to the conclusion – the idea that prebiotics support REM sleep after stress. This may link into another observed function of prebiotics in the body.


One of the most common roadblocks to getting healthy amounts of sleep is stress – the Sleep Council estimates that about half of insomnia is caused by high levels of it. You might be asking yourself how conditions in your digestive system can help change your way of thinking or even begin to tackle such a stubborn issue. The secret may be in serotonin – the neurotransmitter in the brain linked to happiness, satisfaction and more.

Did you know that about 90% of serotonin in the body is made in the gastro-intestinal tract? It’s odd when you first hear it, but serotonin is used in more places in the body than just the brain: it’s used to constrict blood vessels when they’ve been cut, and it regulates bowel movement and hunger. Naturally, an increase of what’s known as “peripheral serotonin” in the blood will also mean an increase in the brain, promoting calmer thoughts and feelings.

Research by Caltech into the link between microbes in the gut and production of serotonin have shown that certain kinds greatly influence its production in cells. With prebiotics like inulin promoting their growth and good health, that has a knock-on effect to levels of serotonin in the body, leading to a happier mind and calmer nights.

Circadian Rhythm

In a more direct way, serotonin affects sleep via the body’s circadian rhythm. This is the internal ‘body clock’ that’s used to determine when energy levels peak and trough during the day. Externally, it’s influenced by light levels and the food we eat before sleeping, but internally serotonin is the major hormone dictating it. It’s synthesised in the brain into melatonin during the night, which prepares the body for sleep.

Of course, with the use of inulin, as mentioned before, levels of serotonin can be increased, ready to be converted into the sleep-inducing melatonin.  If you find yourself feeling awake and energetic in the middle of the night, or lacking energy during the day, perhaps you need to introduce more inulin into your diet.


Research into the bacteria and microbes in the gut is in its infancy. There’s a population of billions of them inside you right now, and scientists are only just now starting to figure out their effect on the digestive system and the body as a whole. Individual species can have different effects when combined with favourable conditions or certain cells within the large intestines, making experimentation slow. The benefits are worth the effort, though, and prebiotics like inulin not only contribute to eased sleep, but may prove to have benefits yet to be discovered.

Now may be a great time to start adding inulin into your diet, whether it’s using it in your coffee or tea, or adding it to your daily smoothie. Even aside from being a sleep aid, inulin can aid your digestive system and is also an excellent source of fibre. If you have any concerns about taking inulin for any reason, consult your doctor to see if it conflicts with any conditions or medication you may be taking.