Sun-dried raisins and gut bacteria in a lab model
What it found
In a lab model of the human gut, sun-dried raisins increased bifidobacteria and lactobacilli and boosted organic acid production.
The work used a simulated digestive tract, not people.
What they found
Animal and lab studies
Beneficial bacteria increased
In the lab model, adding either sun-dried raisins or fructo-oligosaccharides increased the numbers of bifidobacteria and lactobacilli after 8 and 24 hours of fermentation.
Firmicutes and Bacteroidetes decreased
The raisins caused a significant drop in Firmicutes and Bacteroidetes after 8 and 24 hours of fermentation.
Short chain fatty acids
Fructo-oligosaccharides produced the most short chain fatty acids overall. Raisins also increased lactic and acetic acid, and propionic and butyric acid rose after 8 and 24 hours with raisins.
Bacterial diversity
After 24 hours, the raisin samples had 13 fewer species, while the fructo-oligosaccharide samples had 91 more species.
Specific bacteria changes
Faecalibacterium prausnitzii dropped after 4, 8 and 24 hours with raisins. Blautia producta was more abundant in all raisin samples after 24 hours.
What the authors conclude
“Sun-dried raisins demonstrated considerable potential to promote the colonization and proliferation of beneficial bacteria in the human large intestine and to stimulate the production of organic acids.”
Also in their conclusions
- They say sun-dried raisins show considerable potential to promote the colonisation and proliferation of beneficial bacteria in the human large intestine and to stimulate the production of organic acids.
- They call for more in-depth studies on the digestibility of raisins and the long-term effects of raisin supplementation in human test subjects.
How it was done
The authors wanted to see whether sun-dried raisins could affect the mix of bacteria in the human gut, since raisins contain small amounts of fructo-oligosaccharides and other compounds that might reach the large intestine.
They put sun-dried raisins through a lab model that copies chewing, stomach digestion, small intestine digestion and then fermentation in a model of the human large intestine. They compared raisins with fructo-oligosaccharides and with a control that had no added carbon source, and they ran the fermentations three times.
What it can’t tell you
- This was a lab model using faecal material from one healthy donor, not a study in people. It cannot show what would happen in a living human gut.
- The fermentations ran for up to 24 hours, so the results cannot show what would happen with regular raisin eating over weeks or months.
Who paid
- Authors work at
- University of Messina, Italy; Institute of Food Research, UK
The paper
- Title
- The effect of sun-dried raisins (Vitis vinifera L.) on the in vitro composition of the gut microbiota
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Mandalari G, Chessa S, Bisignano C, Chan L, Carughi A (2016). The effect of sun-dried raisins (Vitis vinifera L.) on the in vitro composition of the gut microbiota. Food & function. doi:10.1039/c6fo01137cFree full textPubMed 27713974DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error