Raisins and gut bacteria in 13 healthy adults
What it found
In 13 healthy adults, eating three servings of raisins a day for 14 days did not change the overall mix of gut bacteria.
It did raise or lower the levels of a few specific types of bacteria.
What they found
Studies in people
Overall bacteria mix
The overall variety and mix of gut bacteria did not change much after adding raisins. The authors say the effect on the overall bacterial community was limited.
Bacteria that increased
Some types of bacteria became more common after raisins were added. These included Faecalibacterium prausnitzii, Bacteroidetes sp. and Ruminococcus sp.
Bacteria that decreased
Some types of bacteria became less common after raisins were added. These included Klebsiella sp., Prevotella sp. and Bifidobacterium spp.
Timing of changes
More types of bacteria changed after the first week than after the second week. The authors say this could mean raisins have mostly short-term effects, or that some people found it hard to keep eating the raisins.
Other findings
Possible health links
The authors note that higher levels of Faecalibacterium prausnitzii have been linked to less chronic inflammation and fewer colon polyps. They say future studies are needed to see if these bacterial changes lead to health benefits.
What the authors conclude
“Our findings suggest that adding raisins to the diet can affect the prevalence of specific bacterial taxa.”
Also in their conclusions
- They say their findings suggest that adding raisins to the diet can affect the prevalence of specific bacterial groups.
- They advise that the potential health benefits of these changes should be tested in future studies with clear health outcomes.
- They caution that because this was a small pilot study, the results should be interpreted with caution.
How it was done
Raisins contain plant chemicals and fiber that may help health, possibly by changing gut bacteria. The authors say the effects of eating raisins on gut bacteria had not been well studied in people before.
Thirteen healthy adults aged 18 to 59 ate three servings of sun dried raisins (28.3 g each) every day for 14 days. Stool samples were collected before starting and on days 7 and 14, and the bacteria in them were identified by their DNA.
What it can’t tell you
- This was a small study with only 13 people, so the results may not apply to everyone.
- The study did not measure health outcomes, so it cannot show whether the bacterial changes affect health.
- The study did not include a comparison group that did not eat raisins, so other factors could have caused the changes.
Who paid
- Conflicts
- ETHICS APPROVAL AND CONSENT TO PARTICIPATE: Written informed consent was obtained from all study participants upon enrolment and monetary compensation was provided for each fecal sample provided. This study was conducted according to the guidelines in the declaration of Helsinki, the study protocol was approved by the University of Florida, Institutional Review Board 01. This trial was registered at clinicaltrials.gov as NCT02713165. CONSENT FOR PUBLICATION: All authors provided consent for publication. COMPETING INTERESTS: The authors declare no competing interests. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
- Authors work at
- University of Florida, USA
The paper
- Title
- Dietary raisin intake has limited effect on gut microbiota composition in adult volunteers
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Wijayabahu AT, Waugh SG, Ukhanova M, Mai V (2019). Dietary raisin intake has limited effect on gut microbiota composition in adult volunteers. Nutrition journal. doi:10.1186/s12937-019-0439-1Free full textPubMed 30845997DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error