Chicory: The Roadside Plant That's Caught Diabetes Researchers' Attention

It grows where almost nothing else survives – in the dry gravel along the roadside – and that is exactly why it became one of Europe's most important coffee substitutes. What sits inside the root of chicory is now the subject of a growing number of controlled human trials.

Why did a roadside plant become Europe's best-known coffee substitute?

Chicory (Cichorium intybus) belongs to the daisy family (Asteraceae) and is the wild form from which two quite different crops were bred over the centuries: root chicory, whose roasted root served as a caffeine-free coffee substitute, and the leaf chicories such as Belgian endive, radicchio and curly endive. Its bright blue flowers open in the morning and usually close again by early afternoon – a rhythm that earned the plant the nickname "farmer's clock" in rural areas.

Its German name, Wegwarte ("path-watcher"), traces back to an old folk legend, told in many versions: a woman waits by the roadside for her lover's return and eventually turns into the blue flower that still "waits" along roads and field edges today. What is documented, by contrast, is its history of use: when coffee became scarce across much of Europe during Napoleon's Continental Blockade, roasted chicory root became a household staple – a tradition that persisted in Central Europe well into the 20th century.

What makes the root one of Europe's richest sources of dietary fibre?

Chicory root stores its reserve carbohydrates not as starch but as inulin – a fructan that is not broken down in the small intestine and is only fermented further down, in the colon, by the resident microbiota. Depending on variety and harvest time, inulin makes up roughly 20 percent of the root's fresh weight; measured by dry matter, chicory root ranks among the most fibre-rich vegetables of all. This is precisely what makes it Europe's most important industrial source of inulin – most commercially used inulin comes from chicory grown in north-western Europe.

What do controlled human trials show for digestion and metabolism?

A number of randomised, placebo-controlled human trials on chicory are now available – a remarkably solid evidence base for a roadside plant.

In an RCT (human) involving 47 healthy adults, the intervention group drank 300 ml of a roasted-chicory-root-extract drink daily for four weeks. Fasting blood glucose and insulin did not change significantly, but long-term blood sugar (HbA1c) fell in the chicory group. Adiponectin – a hormone involved in regulating fat and glucose metabolism – rose significantly, and self-reported stool quality tended to improve.

A second RCT (human) with 55 people at elevated risk of type 2 diabetes tested dried chicory root against placebo. Stool frequency and consistency improved measurably, gut microbiota composition shifted substantially, and the bacterial genera Bifidobacterium and Anaerostipes increased three- to four-fold in a dose-dependent, reversible manner. Short-chain fatty acids rose by around 26 percent in stool and around 16 percent in blood; in the subgroup with low baseline levels of the genus Blautia, fasting glucose and the insulin-resistance marker HOMA-IR also decreased.

A third RCT (human) in 49 women with type 2 diabetes specifically tested chicory-root-derived inulin (10 g daily for two months). Compared with placebo, fasting blood glucose fell by around 8.5 percent and HbA1c by around 10.4 percent, while several markers of antioxidant capacity improved.

What role do chicory's bitter compounds play in traditional use?

Chicory's characteristic bitterness comes mainly from sesquiterpene lactones, in particular lactucin and lactucopicrin. On the strength of this long tradition of use, the European Medicines Agency's Committee on Herbal Medicinal Products (HMPC) has recognised chicory root for relieving mild digestive complaints such as a feeling of fullness, flatulence and sluggish digestion, as well as temporary loss of appetite, in adults and children over 12. This classification is explicitly based on traditional use rather than clinical trials – for this type of approval, evidence of at least 30 years of documented safe use, including 15 years within the EU, is sufficient. The traditional classification is supported by a laboratory study showing that chicory root stimulates bile secretion – a plausible mechanism for the bitter compounds' appetite-stimulating and digestion-supporting effects.

In vitro research (lab model) on isolated sesquiterpene lactones such as 11β,13-dihydrolactucin also points to anti-inflammatory potential; the cell models involved, however, remain a long way from clinical application.

What does animal research show for the liver?

A 2023 animal study (preclinical) in rats examined an extract from the above-ground parts of wild chicory – not the root. In animals with experimentally induced acute liver injury, the extract, at doses of 100 or 500 mg/kg body weight, lowered liver enzyme activity as well as bilirubin, glucose and lipid levels; in diet-induced hyperlipidaemia, favourable effects on fat and glucose metabolism were also seen. The results are promising, but given the animal model, plant part used and dosage, they cannot be directly extrapolated to use in humans.

Compound / Aspect	Observation	Study type
Inulin (fructan)	Up to approx. 20% of root fresh weight; substrate for gut bacteria	Analytical / several RCTs
Stool frequency & consistency	Improvement with dried chicory root	RCT, n = 55
Bifidobacterium / Anaerostipes	Dose-dependent, reversible increase	RCT, n = 55
HbA1c / fasting glucose	Decrease in two independent RCTs, in diabetic and healthy participants	RCT, n = 47 / n = 49
Sesquiterpene lactones (lactucin etc.)	Bitter compounds; traditionally linked to bile secretion	Laboratory study / traditional use (HMPC)
Liver enzymes, blood lipids (herb extract)	Improvement after induced liver injury	Animal study (rat)

What should be kept in mind when using chicory?

As a food – for example as roasted chicory "coffee" or as a salad vegetable – chicory is generally considered well tolerated. For more concentrated preparations, a few points are worth noting:

• Daisy-family allergy: As a member of the Asteraceae family, chicory can trigger cross-reactions in people with an existing allergy to related plants such as mugwort, ragweed, dandelion or artichoke.
• Bloating and fullness: The inulin it contains is fermented in the colon and can cause bloating, particularly with a sensitive gut or at higher doses; increasing the amount gradually is advisable.
• Bile ducts: Because bitter compounds traditionally stimulate bile secretion, medical advice is recommended before using higher-dose preparations in the case of gallstones or bile duct obstruction.
• Children, pregnancy and breastfeeding: According to the HMPC, traditional use is intended for adults and children over 12; for younger children and for pregnancy and breastfeeding, there is insufficient data for medicinally dosed preparations.
• Side effects: At the time of the HMPC assessment, no side effects had been reported; even so, review articles describe the overall toxicological data on chicory as limited.

Conclusion: a roadside plant with a remarkably solid evidence base

For a plant more readily associated with roadsides than with laboratories, chicory paints an unusually clear picture: three independent randomised human trials consistently show how the root supports bowel habits, gut microbiota and short-chain fatty acids – and deliver solid signs of favourable effects on blood glucose parameters, particularly in people at elevated risk of diabetes. Its centuries-old traditional use for digestive complaints and appetite loss is now formally recognised by the HMPC, a fitting example of accumulated experience and modern research meeting in the middle. The first animal findings on the liver open up a promising new line of research: whether these effects also hold in humans is likely to be one of the most exciting next chapters in the study of this unassuming blue roadside companion.

This article is for general information only and does not replace medical advice. If you have health concerns, or before using higher-dose preparations, please consult a doctor or pharmacist.