Rhubarb compounds, gut bacteria and colon damage in rats
What it found
A breakdown product called rhein built up in rat colons after 90 days of rhubarb extracts and damaged colon cells in lab tests.
Gut bacteria from treated rats made more rhein than those from untreated rats.
What they found
Animal and lab studies
Tolerance built up in rats
The rats needed much higher doses over time to keep their stools loose. By the end of the 90 days, the dose was 10 times the starting amount of 48.25 mg/kg, reaching 482.5 mg/kg per day.
Weight loss in rats
Control rats gained 18.62% of their body weight over the study. The rats given rhubarb extract lost 3.38% of their starting weight.
Colon damage in rats
After 90 days, the treated rats had brown pigment deposits in their colon lining, fewer mucus-producing cells and signs of inflammation. Their colons and stomachs were heavier relative to body size than those of control rats.
Rhein built up over time
Gut bacteria turned the main rhubarb compound into several breakdown products. One called rhein accumulated the most, reaching 66.62 μg/g in rat droppings by day 80. Bacteria from treated rats produced more rhein than bacteria from control rats.
Cell damage in lab dishes
When human colon cells were exposed to rhein, cell growth slowed. At 40 μM, 77.76% of normal colon cells survived, compared with only 27.70% of colon cancer cells. Rhein caused normal colon cells to break down their own parts and triggered DNA damage at higher amounts.
What the authors conclude
- They conclude that rhein, made by gut bacteria from rhubarb compounds, is the most likely cause of colon damage seen after long-term use.
- Their results suggest that finding ways to reduce rhein build-up in the colon might help lower the risk of harm.
How it was done
Rhubarb is eaten as food and used to treat constipation, but long-term use has been linked to a dark pigmentation of the colon lining. The authors wanted to find out which specific breakdown product causes this change.
They gave 8 male rats a daily dose of rhubarb extract for 90 days, while 8 control rats received water. They checked the animals' weight, stool water content and colon tissue. They also tested how gut bacteria broke down the extract, and exposed human colon cells to the breakdown products in lab dishes.
What it can’t tell you
- These findings come from rats and lab dishes, so they cannot show exactly what happens in people who eat rhubarb.
- The researchers gave rats concentrated extract at high doses, which may not match how much rhubarb a person eats as food.
Who paid
- Conflicts
- Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
- Authors work at
- Northwest University, China; University of Leeds, UK; Jiangsu University, China
The paper
- Title
- Identification of rhein as the metabolite responsible for toxicity of rhubarb anthraquinones
- Type
- Study
- Evidence
- Animals and lab studies
- Summarised from
- Full text
- Cite
- Cheng Y, Zhang H, Qu L, et al (2020). Identification of rhein as the metabolite responsible for toxicity of rhubarb anthraquinones. Food chemistry. doi:10.1016/j.foodchem.2020.127363Free full textPubMed 32590269DOI
Summary written 1 Oct 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error