A 2022 study showed significant improvements in fasting glucose, A1c, and lipid profile vs placebo. A 2023 umbrella review confirmed these trends but noted that the observed A1c decrease — around 0.1 percentage points — is unlikely to be clinically meaningful. More recent randomised trials, according to another meta-analysis, point to slight improvements in various metabolic parameters, but without a clear effect on insulin levels. Many studies were conducted under very different conditions, further complicating comparison and interpretation.
On average, the observed effects are small; studies are often short (mostly 8-16 weeks), with limited sample sizes and substantial heterogeneity. Differences include the type of cinnamon (cassia vs Ceylon), dose (from a few hundred milligrams to 6 g per day), formulation (powder, extract, or capsule), and populations studied (prediabetes, newly diagnosed type 2 diabetes, or metabolic syndrome). Many studies have methodological weaknesses, such as insufficient blinding, unclear adherence, or concurrent lifestyle changes that could skew results.
The German Diabetes Society therefore states that culinary use of cinnamon is unproblematic but explicitly advises against using cinnamon preparations to lower blood glucose. The benefit is not sufficiently proven.
There is also a toxicologic aspect: Many commercial preparations are based on cassia cinnamon, which contains significantly higher amounts of coumarin. Coumarin can damage the liver at high doses over longer periods. The European Food Safety Authority has set a tolerable daily intake of 0.1 mg of coumarin per kilogram of body weight, which should not be exceeded on an ongoing basis. Dietary supplements can easily exceed this limit, often without listing the exact content.
Cinnamon in Neurology: Many Questions
Assessing potential neuroprotective effects is even more speculative. Preclinical studies show antioxidant, anti-inflammatory, and neuroprotective properties of various cinnamon constituents. These compounds reduce aggregation of amyloid-beta and tau proteins in models, modulate signalling pathways such as SIRT1 or nuclear factor-kappa B, and promote neuronal survival.
There are promising animal studies in Parkinson’s disease: Mice given cinnamon showed upregulation of the proteins DJ-1 and Parkin and protection of dopaminergic neurons. DJ-1 and Parkin have protective properties. Older investigations suggest possible positive effects in traumatic brain injury, stress-induced mood changes, or cognitive functions — again, exclusively in preclinical work.In September 2021, researchers searched PubMed, Scopus, Google Scholar, and Web of Science, identifying 2605 potentially relevant studies on neuroprotection. After detailed screening, 40 studies met all criteria for their systematic review: 33 animal studies, five in vitro analyses, and two clinical investigations.
In vivo studies using different animal models indicate that cinnamon and its components — such as eugenol, cinnamaldehyde, and cinnamic acid — can meaningfully improve brain function. In vitro studies support this picture: When researchers add cinnamon or cinnamaldehyde to cell cultures, tau and amyloid-beta deposits are reduced, and cells show higher survival rates.
Clinical studies, however, have yielded mixed results. Some report clear improvements in cognitive performance, while another found no changes. Until results from high-quality clinical trials are available, it is too early to make recommendations.
Metabolism, Inflammation, and the Microbiome
Beyond neurology and diabetology, cinnamon is drawing attention in other medical areas. Researchers have shown that cinnamon may improve lipid levels, triglycerides, or certain inflammatory markers in patients. These effects are attributed to antioxidant properties and possible influences on the gut microbiome. Robust clinical data to clearly confirm these findings are stilllacking.
Cinnamon also shows antimicrobial effects in vitro. Whether practical medical applications — such as for gastrointestinal complaints or mucosal infections — can be developed remains uncertain. Experts likewise judge possible mood-stabilising effects cautiously, as supporting evidence to date comes only from animal studies.
Enjoy as a Spice — Don’t Treat as Medication
Cinnamon is a time-honoured spice with pharmacologically relevant constituents. Scientific evidence shows metabolic and neuroprotective effects in preclinical models and small improvements in blood glucose in clinical studies. But the strength of the evidence is limited.
Professional societies therefore clearly advise against using cinnamon preparations to treat diabetes. In neurology, it remains an experimental research field without clinical relevance at this time.
For everyday life, a simple recommendation stands: Enjoy cinnamon as a delicious spice — but don’t treat it as a medical preparation.
Cinnamon: Tips for counselling
- Cinnamon in normal culinary amounts is unproblematic for healthy individuals.
- Ceylon cinnamon is considered the better choice due to its much lower coumarin content.
- High-dose cinnamon preparations can be risky, especially for individuals with liver disease, for pregnant women, for children, and for patients taking medications.
- Experts explicitly advise against using cinnamon preparations as a diabetes therapy or adjusting medications on one’s own.
- The evidence is even weaker for neurologic or infectious indications.
