Sleep starts in the gut

Most of the serotonin in your body isn't made in your brain; it's made in your belly. Serotonin is the raw material for melatonin, the hormone that controls your sleep clock, and about 90% of your serotonin comes from the cells lining your gut — with a lot of help from the creepy-crawly bacteria living there (Yano et al., Cell, 2015). That gives digestion more say over your sleep than you'd expect, and raises a key question: what are you feeding your little goggas?

Food for your inner ecosystem

Chicory root is one of the richest plant sources of inulin (not to be confused with insulin). Inulin is a type of fibre humans can't digest, but that our gut bacteria can. In fact, the molecular structure of inulin is preferred by a wide array of beneficial gut bacteria, which makes it a prebiotic, a substance that helps to stabilise and regulate your inner microbial ecosystem. When your gut microbes break inulin down, they release short-chain fatty acids — the same compounds that switch on the gut cells that make serotonin. Feed the bacteria, and you supply the front end of a chain that ends, a few steps later, in more melatonin and a steadier nervous system.

What the studies show

In a 2023 placebo-controlled trial in the American Journal of Clinical Nutrition, adults with mild-to-moderate anxiety took 8 grams of chicory-derived inulin a day for five weeks. They came out less anxious, in better spirits, and with a smaller morning spike in cortisol, the body's main stress hormone (Jackson et al.). The study didn't track sleep, but having consistently elevated stress levels is one of the surest ways to end up staring at the ceiling at 2 a.m., and turning the volume down tends to make sleep come easier.

Ye olde evening drink

None of this would have surprised the old herbalists. Ancient physicians like Dioscorides called chicory a cooling herb — the old-timey term for something that calms rather than stimulates. Almost two thousand years later, when the French began blending chicory with coffee, it came to be known as a *contra stimulante*, a substance that could blunt the hyper-stimulating, nervous energy of coffee. Roasting, the French found, also took the edge off the otherwise intolerably bitter root, giving it a subtly sweet, woody-nutty flavour very similar to coffee. For a coffee lover, it is these characteristics that make chicory an ideal stand-in for that late afternoon cup, given what we now know about the negative impact of residual caffeine on REM sleep.

The famed Café du Monde in New Orleans, where chicory-blended coffee has been served since 1862

Worth a shot?

As it turns out, the inulin in chicory survives the roasting process very well. This gives the act of drinking chicory a two-pronged character as a potential sleep enhancing intervention: it can be used both as a pleasant way to displace excessive caffeine (by satisfying your craving for the flavour and ritual of coffee), and as a supplement that can enhance your body's ability to sink into and stay in deep sleep. The sources that suggest this — ancient Greek physicians, 19th century Frenchmen, modern scientific trials — come from very different ways of thinking about the world, yet land up in the same place.

The final test, of course, lies with each of us to self-experiment and observe how the effects accumulate over days and weeks after implementing a new behaviour. Roasted chicory doesn't have strong sedative properties, meaning it can be enjoyed (by you and your microbes) at any time of day, as often as you like. At the same time, enjoying a warm cup of something as a winding down ritual — an anchor that leads into your pre-sleep routine — is another well-evidenced way to improve your ability to get yourself to head for bed and fall asleep at a regular time. Why not stack the odds in your favour, and make it a nice cup of chicory?