The Study
The effects on plasma L-arginine levels of combined oral L-citrulline and L-arginine supplementation in healthy males
This study showed that when healthy guys took two supplements together, their blood had more of a certain chemical than when they took just one. It’s like proving that mixing two juices gives you more sugar than drinking either one alone — but it doesn’t tell us if that makes you healthier.
Analysis score
Maximum 45 for a randomized controlled trial.
Where the score came from
Taking half a gram of one amino acid plus half a gram of another works better than taking two grams of just one — like mixing two keys to unlock more of a nutrient.
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 545 / 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 — this means combining them gives a stronger, faster boost to L-arginine, which your body uses to make nitric oxide, even if nitric oxide didn't rise in this short test.
- 2Combining 1 g L-citrulline + 1 g L-arginine raised blood L-arginine 25% more than 2 g of either alone, with peak levels at 1 hour.
- 3L-citrulline alone lasted longer but rose slower.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Bioscience, Biotechnology, and Biochemistry
Year
2017
Authors
Takashi Suzuki, M. Morita, Toshio Hayashi, A. Kamimura
Related Content
Claims (4)
In healthy Japanese men aged 20–49, taking 1 gram of L-citrulline and 1 gram of L-arginine together raises plasma L-arginine levels more than taking 2 grams of either amino acid separately, with a 25% higher area under the curve and higher peak concentration at one hour after ingestion.
When healthy men take 1 gram of L-citrulline and 1 gram of L-arginine together, their blood L-arginine levels reach a higher peak after one hour than when they take 2 grams of either amino acid by itself.
Taking L-citrulline and L-arginine together reduces the enzyme that breaks down L-arginine, resulting in higher levels of L-arginine in the blood.
Taking L-citrulline and L-arginine supplements orally does not increase plasma nitrite and nitrate levels in healthy men, showing that higher plasma L-arginine does not lead to higher nitric oxide production over a short period.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.