Hemp fiber, gut permeability and blood metabolites after cycling
What it found
In 23 cyclists, taking hemp fiber bars for 2 weeks did not change gut permeability after a long, hard ride.
It did shift many substances in the blood, including some made by gut bacteria.
What they found
Studies in people
Gut permeability
The main measure of gut permeability, the urine lactulose to 13C mannitol ratio, did not differ between the hemp fiber and placebo trials. The authors say the exercise-induced changes in this ratio were modest and variable.
Muscle damage and stress
Markers of muscle damage (creatine kinase, myoglobin) and the stress hormone cortisol rose after exercise, but the pattern over time was the same in all three trials.
Blood metabolites
An analysis of many substances in the blood showed clear differences between the hemp fiber trials and placebo. Several metabolites were identified as important for telling the trials apart, including 3-hydroxy-4-methoxybenzoic acid, serotonin, 5-hydroxytryptophan, and 4-methoxycinnamic acid.
Metabolic pathways
Hemp fiber intake affected several metabolic pathways, including those for alpha-linolenic acid, porphyrin, sphingolipid, arginine and proline, tryptophan, and primary bile acid metabolism.
Symptoms and tolerance
Gastrointestinal, mental health, respiratory, and sleep symptoms did not differ between the hemp fiber and placebo periods. Participants took over 98.5% of the bars.
What the authors conclude
“The combination of consuming nutrient-rich hemp fiber bars and intensive exercise increased levels of beneficial metabolites, including those derived from the gut in healthy cyclists.”
Also in their conclusions
- They conclude that a 2-week intake of hemp hull fiber did not influence the modest changes in gut permeability after 2.25 hours of vigorous cycling.
- They report that the combination of hemp fiber bars and intensive exercise increased levels of beneficial metabolites, including those derived from the gut, in healthy cyclists.
- They state that the combination had a selective effect on gut permeability and a significant influence on lipid-, bile acid-, and amino acid-related metabolic pathways.
How it was done
The authors wanted to test whether hemp fiber, which is rich in two compounds called NCT and NFT, could affect the gut changes that happen after intense exercise. Lab and animal studies had suggested these compounds might help the gut barrier.
They studied 23 male and female cyclists in a randomized, double-blind, crossover trial. Each person took high-dose (20 g/day) or low-dose (5 g/day) hemp hull powder bars or placebo bars for 2 weeks, with 2-week washouts between. At the end of each period, they cycled for 2.25 hours and gave blood and urine samples.
What it can’t tell you
- The study lasted only 2 weeks per supplement period, so it cannot show what might happen with longer use.
- The results are from healthy, trained cyclists doing a specific 2.25-hour ride, so they may not apply to other people or types of exercise.
- The metabolite changes were measured in blood, but the study cannot prove they cause any health benefit.
Who paid
- Funding
- Funded by NIDDK NIH HHS; Brightseed Inc. (from the PubMed record).
- Conflicts
- The authors declare no conflicts of interest. The authors declare that this study received funding from Brightseed, Inc. The funder was not involved in the study design, collection, analysis, interpretation of data, the writing of this article or the decision to submit it for publication.
- Authors work at
- Appalachian State University, USA; University of North Carolina at Chapel Hill, USA
The paper
- Title
- Selective Influence of Hemp Fiber Ingestion on Post-Exercise Gut Permeability: A Metabolomics-Based Analysis
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Nieman DC, Sakaguchi CA, Williams JC, et al (2025). Selective Influence of Hemp Fiber Ingestion on Post-Exercise Gut Permeability: A Metabolomics-Based Analysis. Nutrients. doi:10.3390/nu17081384Free full textPubMed 40284247DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error