Glycerol in food and acrolein made by gut bacteria
What it found
In 20 people living under controlled conditions for 11 days, meals with more glycerol led to higher levels of acrolein-related substances in their urine.
The authors say gut bacteria turning glycerol into acrolein may explain this.
What they found
Studies in people
Glycerol in meals
Every meal contained glycerol. Men took in 3.8 to 6.3 grams a day and women 3.6 to 5.8 grams a day, with the amount varying by meal and day.
Gut bacteria could use glycerol
Stool samples from all volunteers had bacteria with the genetic ability to turn glycerol into acrolein. Anaerobutyricum was the main group doing this across donors and time.
Glycerol found in stool
Glycerol was detected in all stool samples, at levels from 0.2 to 19.4 micromoles per gram. This shows glycerol was available to gut bacteria.
Urine markers after high glycerol
After dinners with high glycerol, levels of two acrolein-related substances in urine (3-HPMA and CEMA) were higher than after low-glycerol dinners. The authors say this points to gut bacteria turning glycerol into acrolein.
Two urine patterns
Most volunteers (14 of 20) usually had more 3-HPMA than CEMA in their urine. The other 6 usually had more CEMA. These patterns were linked to differences in gut bacteria and fermentation products.
Estimated acrolein levels
The authors estimated that only a small share of the glycerol was turned into acrolein, and that overall levels of acrolein in the gut were low. Most acrolein was not recovered in urine, possibly because it reacts quickly with other molecules.
What the authors conclude
“Fat/glycerol intake with the diet together with intestinal microbiota activity might temporarily increase endogenous acrolein formation; however, overall levels of intestinal acrolein were estimated as low.”
Also in their conclusions
- They say the potential for gut bacteria to turn glycerol into acrolein is common in people.
- They conclude that eating fat and glycerol together with gut bacterial activity might temporarily raise the body's own acrolein formation, but that overall levels were estimated as low.
- They suggest a link between intestinal acrolein and the gut and kidney.
How it was done
Acrolein has been linked to diabetes, heart, lung and brain diseases. The authors wanted to find out how much gut bacteria add to the body's own acrolein by turning glycerol from food into it.
They housed 20 non-smoking volunteers (10 men, 10 women) for 11 days and gave them a controlled diet with no fried or baked foods. Glycerol was in every meal, and the researchers measured glycerol in stool and acrolein-related substances in urine.
What it can’t tell you
- This study followed people over 11 days and can show a link between glycerol intake and acrolein markers, but it cannot prove that glycerol caused the acrolein.
- The authors estimated acrolein levels using a ratio from rat studies, so the human estimates may not be exact.
- The study did not measure acrolein directly in the gut, only its breakdown products in urine.
Who paid
- Funding
- Funded by Deutsche Forschungsgemeinschaft DFG (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Aarhus University, Denmark; RPTU University Kaiserslautern-Landau, Germany; Technical University of Denmark, Denmark
The paper
- Title
- Microbial Transformation of Dietary Glycerol Contributes to Intestinal Acrolein Formation and Urinary Excretion
- Type
- Study
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Schwab C, Lang H, Stegmüller S, et al (2025). Microbial Transformation of Dietary Glycerol Contributes to Intestinal Acrolein Formation and Urinary Excretion. Molecular nutrition & food research. doi:10.1002/mnfr.70289Free full textPubMed 41159664DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error