Black cumin extract and gut bacteria in lab tests
What it found
In lab tests using human stool samples, black cumin extract increased the production of three short-chain fatty acids and boosted certain gut bacteria.
Turmeric and cinnamon extracts had much smaller effects.
What they found
Animal and lab studies
Short-chain fatty acids
Black cumin extract increased acetate by 8.7 mM, butyrate by 1.3 mM, and propionate by 3 mM compared with the control. Turmeric and cinnamon extracts did not change total short-chain fatty acid levels.
Specific gut bacteria
Black cumin extract increased Alistipes onderdonkii, Alistipes shahii, and especially Candidatus Cibiobacter qucibialis. It decreased Bacteroides ovatus and several other species.
Cinnamon effects
Ceylon cinnamon extract increased Faecalibacterium prausnitzii, Enterococcus species, and Veillonella parvula, while decreasing Bacteroides ovatus and other species. It also slightly reduced total bacterial cell counts, but this was not statistically significant.
Turmeric effects
Turmeric extract had the smallest effect on gut bacteria. It significantly decreased Parabacteroides distasonis, Alistipes shahii, and Alistipes onderdonkii, but increased beneficial species like Faecalibacterium prausnitzii and Dysosmobacter welbionis, though these increases were not statistically significant.
Overall community
None of the extracts significantly changed the overall diversity or community structure of the gut bacteria. Black cumin made the communities from different donors more similar to each other.
What the authors conclude
“Overall, these findings indicate these spices may have an impact on the human gut microbiome that could explain their purported health effects.”
Also in their conclusions
- They conclude that black cumin extract caused the largest increase in metabolic function of the gut microbiota, while turmeric had very small effects.
- They say these findings indicate the spices may have an impact on the human gut microbiome that could explain their purported health effects.
How it was done
The authors wanted to see if these spices affect the human gut bacteria, since many of their claimed gut health benefits have not been tested in people.
They collected stool samples from 6 healthy adults and grew the gut bacteria in the lab for 48 hours with extracts of black cumin, turmeric, or Ceylon cinnamon, each at a dose of 3 grams per litre. They then measured bacterial DNA, cell counts, and the fatty acids produced.
What it can’t tell you
- This was a lab study using stool samples, not people. It cannot show what happens when someone eats these spices.
- The extracts were tested at a higher dose than would typically be used as a supplement, so the results may not reflect normal use.
Who paid
- Conflicts
- This work was supported by the USDA In-House Project 8072-41000-108-00-D, “In Vitro Human Intestinal Microbial Ecosystems: Effect of Diet”. This research used resources provided by the SCINet project of the USDA Agricultural Research Service, ARS project number 0500-00093-001-11-D. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
- Authors work at
- Eastern Regional Research Center, United States of America; University of Maryland, United States of America
The paper
- Title
- The ex vivo effects of ethanolic extractions of black cumin seed, turmeric root, and Ceylon cinnamon bark on the human gut microbiota
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Licence
- Public domain. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Mahalak KK, Narrowe AB, Liu L, et al (2025). The ex vivo effects of ethanolic extractions of black cumin seed, turmeric root, and Ceylon cinnamon bark on the human gut microbiota. PloS one. doi:10.1371/journal.pone.0334824Free full textPubMed 41343511DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error