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Culinary spices

Culinary spices such as cinnamon, ginger and garlic have long histories in folk and traditional medicine, and several have been tested in randomised trials, mostly as concentrated supplements rather than as food. Trials suggest small improvements in blood glucose markers with cinnamon in adults with type 2 diabetes, less nausea with ginger in pregnancy and lower blood pressure with garlic in adults with high blood pressure, and a large Chinese cohort linked regular spicy food with lower mortality. None of these findings reaches moderate certainty, because the trials are small, varied in product and dose, and highly heterogeneous, and the mortality evidence is observational. Spices in food amounts are generally regarded as safe; heavy use of cassia cinnamon can bring coumarin intake up to the tolerable daily intake.

Evidence retrieved up to

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5 research claims, 1 tradition claim

Research5Tradition1
Marks

What the research shows

In randomised trials in adults living with type 2 diabetes, cinnamon supplements modestly lowered fasting blood glucose, HbA1c and insulin resistance compared with control, though results varied widely between trials.

No known concerns at usual amountsBenefit

Who this is about

adults living with type 2 diabetes

Details and sources

Practical note

Graded low: randomised trials (a 2025 meta-analysis of 28 RCTs and a 2024 meta-analysis of 24 RCTs) downgraded for very high heterogeneity (I2 up to 100%) and for indirectness, since products often did not state which cinnamon species or plant part was used. Most trials gave cinnamon in capsules for 30 to 120 days; the 2025 review reported effects for doses at or below 2 g a day and above it.

Vegan note

Cinnamon is plant-derived; capsule products may use gelatine shells.

Safety note

Cassia cinnamon, the most common type sold in North America, contains coumarin; see the coumarin claim in this topic.

Sources

In randomised trials in pregnant women, ginger reduced nausea symptoms compared with placebo, but did not clearly reduce the number of vomiting episodes.

No known concerns at usual amountsBenefit

Who this is about

pregnant women with nausea and vomiting of pregnancy

Details and sources

Practical note

Graded low: 12 RCTs with 1278 women, consistent for nausea (I2 = 0%) but downgraded for risk of bias and variable outcome reporting (the authors describe the evidence as low quality) and for imprecision. Most trials tested supplements rather than food; subgroup analyses favoured daily doses below 1500 mg.

Vegan note

Ginger is plant-derived; capsule products may use gelatine shells.

Safety note

The meta-analysis found no significant increase in spontaneous abortion, heartburn or drowsiness, but the trials were few and small. NCCIH notes ginger can cause abdominal discomfort, heartburn and diarrhoea, and that little is known about use while breastfeeding.

Sources

In randomised trials, garlic supplements lowered systolic and diastolic blood pressure compared with placebo, with larger reductions in adults with high blood pressure.

No known concerns at usual amountsBenefit

Who this is about

adults with high blood pressure

Details and sources

Practical note

Graded low: a single-author meta-analysis of 20 trials with 970 participants, downgraded for imprecision (small trials), indirectness (mixed supplement preparations rather than culinary garlic) and possible publication bias from a Medline-only search.

Vegan note

Garlic is plant-derived; some aged garlic and garlic oil products use gelatine capsules.

Safety note

The review describes garlic supplements as highly tolerated; the trials did not assess cardiovascular events.

Sources

In a large cohort of Chinese adults, eating spicy foods on most days of the week was associated with lower total mortality over about seven years than eating them less than once a week.

No known concerns at usual amountsBenefit

Who this is about

adults aged 30 to 79 in China

Details and sources

Practical note

Graded low: one large prospective cohort (487,375 adults, median 7.2 years), observational and with spicy food intake self-reported once at baseline, so residual confounding cannot be excluded. The adjusted hazard ratio was 0.86 for eating spicy food 6 or 7 days a week.

Vegan note

Spices are plant-based seasonings, though the dishes they flavour may not be.

Sources

Cinnamon in usual food amounts is regarded as likely safe, but cassia cinnamon contains coumarin, and heavy consumers of cassia cinnamon may reach the tolerable daily intake of coumarin.

Take care: see the safety noteRisk

Who this is about

adults who consume large amounts of cassia cinnamon

Safety note

Coumarin can affect the liver in a susceptible subgroup of people; NCCIH notes prolonged use of cassia cinnamon could be an issue for people with liver disease. Ceylon cinnamon contains only trace coumarin.

Details and sources

Practical note

Graded low: based on a risk assessment that derived a tolerable daily intake of 0.1 mg coumarin per kg body weight from clinical data on coumarin given as a drug, combined with a survey of more than 1000 people in Germany; direct evidence of harm from culinary cinnamon is limited.

Sources

What the tradition holds

Folk medicine traditions have used ginger since ancient times, including for indigestion and gastrointestinal discomfort.

No known concerns at usual amountsUnclear

Who this is about

adults using ginger in traditional practice

Details and sources

The tradition's frame

Other

Folk medicine has used ginger since ancient times as a remedy for a range of complaints, including flu and gastrointestinal discomfort.

Practical note

This records a traditional use; it is not graded.

Vegan note

Fresh and dried ginger root are plant foods.

Safety note

Oral ginger can cause abdominal discomfort, heartburn, diarrhoea and mouth and throat irritation.

Sources