In plain terms: Cinnamon (Cassia / Ceylon) has some human trial evidence supporting it, but the evidence is not yet strong enough for EBL to call it established. It is worth knowing about and worth discussing with your clinician.
Cinnamon (Cassia / Ceylon)
The evidence as the record states it
Allen et al. (Annals of Family Medicine, 2013; PMID 24019277) and de Moura et al. (Nutrition Reviews, 2025; PMID 38917435): meta-analyses: cinnamon modestly lowered fasting glucose and some lipid markers in type 2 diabetes; HbA1c effects were less consistent. Grade B: meta-analytic RCT evidence, modest glycemic effect.
Why Grade B and not Grade A
Grade B reflects moderate human evidence -- typically a single strong trial, multiple smaller trials, or surrogate endpoint data without hard clinical outcome replication. To reach Grade A, Cinnamon (Cassia / Ceylon) would require at least one additional independent randomized trial demonstrating a hard clinical endpoint or objectively measured functional outcome in a comparable population.
What would move this grade
An independent randomized trial demonstrating a hard clinical endpoint -- mortality, major adverse event, or objectively confirmed functional improvement -- in an adequately powered sample, with results independently replicated, would support Grade A.
How this was studied
Form: Cinnamon supplementation, oral, compared with placebo or control (Allen 2013 meta-analysis, PMID 24019277; de Moura 2025 meta-analysis, PMID 38917435); capsule form was analyzed as a subgroup (de Moura 2025, PMID 38917435). Species (cassia or Ceylon) is not stated in the cited abstracts. · Dose: 120 mg/day to 6 g/day (Allen 2013, PMID 24019277); doses analyzed as 2 g/day or less and more than 2 g/day (de Moura 2025, PMID 38917435). · Population: Patients with type 2 diabetes: 10 trials, 543 patients (Allen 2013, PMID 24019277); 28 trials, 3054 adults and elderly patients (de Moura 2025, PMID 38917435). Age range and sex mix are not stated in the cited abstracts. · Duration: 4 to 18 weeks (Allen 2013, PMID 24019277); 30 to 120 days (de Moura 2025, PMID 38917435).