The Study
The Effects of L-Citrulline on the Apparent Digestion and Metabolism of Nutrients, Blood Hormone Levels, Amino Acid Metabolism and the Diversity of Faecal Microbiota in Mares in the Later Stage of Pregnancy
This study gave different amounts of a supplement to pregnant horses and saw what changed in their bodies. It shows that the supplement might help them digest food better and feel less stressed, but only in these horses — we don’t know if it would work the same in people or other animals.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists gave pregnant horses a special amino acid called citrulline to see if it helped them digest food better and stay healthier during pregnancy.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 519 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — better digestion and less stress mean the mother horse can support her growing foal more effectively, potentially leading to healthier births.
- 2Horses given 30 grams per day digested protein and fiber better, had 11% less oxidative stress, 15% more pregnancy hormone, and more good gut bacteria.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Life
Year
2026
Authors
Pengshun Liu, Fan Yang, Jiahao Li, Chao Li, X. Guo, Xiaobin Li
Related Content
Claims (6)
Citrulline increases the liver's ability to remove ammonia from the blood and extends the time the body can use oxygen for energy during exercise.
In late-pregnant Yili mares, daily intake of 30 grams of L-citrulline increases the efficiency of protein and fiber digestion, raises the rate of nitrogen metabolism by 19.97%, boosts superoxide dismutase activity by 10.90%, and lowers malondialdehyde levels by 11.53%.
In late-pregnant Yili mares, daily intake of 30 grams of L-citrulline raises plasma estradiol levels by 14.81% and increases urinary conjugated estrogens, reflecting higher estrogen production and metabolic activity during late pregnancy.
In late-pregnant Yili mares, daily intake of 30 grams of L-citrulline increases the diversity of gut bacteria and raises the abundance of specific bacterial groups including Lachnospiraceae, Saccharofermentans, and Fibrobacter.
In late-pregnant Yili mares, 30 grams of L-citrulline per day leads to the best overall health score based on nutrient digestion, antioxidant levels, hormone concentrations, and gut bacteria, compared to 15 grams or 45 grams per day.
When late-pregnant Yili mares receive 30 grams of L-citrulline daily, their blood levels of citrulline and arginine rise by more than 50%, and levels of ornithine, histidine, leucine, and glutamate also increase, reflecting greater activity in the urea cycle and altered amino acid metabolism.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.