Carrageenan, insulin resistance and gut permeability in men
What it found
In 20 young men, two weeks of carrageenan did not change insulin sensitivity overall, but those with a higher BMI had lower insulin sensitivity and signs of inflammation.
Carrageenan also increased intestinal permeability.
What they found
Studies in people
Insulin sensitivity overall
Whole-body insulin sensitivity measured by oral glucose tolerance test and clamp did not differ between carrageenan and placebo. Hepatic insulin sensitivity was also unchanged.
Higher BMI and insulin
In participants with higher BMI, carrageenan led to lower whole-body and hepatic insulin sensitivity and higher fasting insulin resistance compared to placebo. No effect was seen on skeletal muscle insulin sensitivity.
Gut permeability
The lactulose-mannitol ratio was higher during carrageenan intake, indicating increased intestinal permeability. Plasma zonulin was also higher after carrageenan (55.9 vs 52.1 ng/l).
Inflammation markers
Overall, C-reactive protein and interleukin-6 did not differ between treatments. In participants with higher BMI, carrageenan was associated with elevated CRP and IL-6.
Brain inflammation
Hypothalamic inflammation showed a trend toward an increase with carrageenan in overweight participants, but no overall difference between treatments.
Animal and lab studies
Immune cells in lab
When immune cells from participants were exposed to carrageenan in the lab, natural killer cells and B cells were activated and pro-inflammatory cytokines were released.
What the authors conclude
“These findings suggest that carrageenan, a common food additive, may contribute to insulin resistance and subclinical inflammation in overweight individuals through pro-inflammatory mechanisms in the gut.”
Also in their conclusions
- They conclude that increased carrageenan intake can disrupt intestinal barrier function in humans.
- They state that the results warrant caution with carrageenan-containing foods, especially in individuals who are prone to develop type 2 diabetes.
- They call for further studies to test carrageenan's effects in a population at increased risk.
How it was done
The authors wanted to test whether carrageenan, a common food additive that causes insulin resistance and gut inflammation in animals, has similar effects in people.
They ran a randomised, double-blind, placebo-controlled cross-over trial in 20 young non-obese men. Each man took 250 mg of carrageenan or a placebo twice daily for 2 weeks, with a washout period in between.
What it can’t tell you
- The study only included young, healthy males, so the results may not apply to women, older people, or those with existing health conditions.
- The short 2-week exposure periods cannot show what might happen with long-term carrageenan intake.
- The trial cannot prove that carrageenan causes type 2 diabetes, only that it was linked to some changes in the short term.
Who paid
- Conflicts
- Declarations. Ethics approval and consent to participate: The study was approved by the Ethical Committee of the Medical Faculty of the University of Tübingen, Germany (project number 359/2012BO1). All participants provided written informed consent. Consent for publication: All authors have reviewed and approved the manuscript for submission. Competing interests: RW reports lecture fees from NovoNordisk, Eli Lilly, Boehringer-Ingelheim and Sanofi, and travel grants from Eli Lilly, Sanofi and NovoNordisk. He served on the advisory board of Akcea Therapeutics, Daiichi Sankyo, Sanofi and NovoNordisk. Outside of the current work, MH reports research grants from Boehringer Ingelheim and Sanofi to the University Hospital of Tübingen, participation in advisory board for Boehringer Ingelheim and Sanofi and lecture fees from Amryt, Bayer, Sanofi, Eli Lilly, Novo Nordisk and Boehringer Ingelheim.
- Authors work at
- University Hospital of Tübingen, Germany; Institute for Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Centre Munich at the University of Tübingen, Germany; German Center for Diabetes Research (DZD), Germany
The paper
- Title
- Carrageenan and insulin resistance in humans: a randomised double-blind cross-over trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Wagner R, Buettner J, Heni M, et al (2024). Carrageenan and insulin resistance in humans: a randomised double-blind cross-over trial. BMC medicine. doi:10.1186/s12916-024-03771-8Free full textPubMed 39593091DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error