Citable fact
«Arginine» — evidence level C. Dosage: 3–6 g per day in several doses at minimum; studies used doses up to 6–12 g. Even high oral doses give a smaller effect than 6–8 g of citrulline. Source: PMID 34965876, permanent link to the source in the list below.
How it works
Arginine is a substrate of the enzyme NO synthase, from which nitric oxide, which dilates blood vessels, is formed. This is exactly what the idea of improving blood flow and oxygen delivery is built on. The problem lies in the pharmacokinetics: when taken orally, a significant part of arginine is destroyed in the intestine and liver by the enzyme arginase before it reaches the bloodstream. Therefore plasma arginine concentration rises only slightly, and the increase in nitric oxide turns out to be insignificant. Citrulline bypasses this barrier: it passes through the liver and is converted to arginine already in the kidneys, providing a more pronounced and stable rise in concentration.
Dosage and intake
3–6 g per day in several doses at minimum; studies used doses up to 6–12 g. Even high oral doses give a smaller effect than 6–8 g of citrulline
In divided doses during the day or 60–90 minutes before training. A single large dose is tolerated worse than a divided one
Forms
L-arginine in powder or capsules. Sustained-release forms and precursors such as arginine alpha-ketoglutarate do not fully solve the problem of hepatic breakdown. The alternative is citrulline malate
What is confirmed
- Theoretically supports nitric oxide formation and blood flow
- Part of ordinary protein and participates in the synthesis of creatine and urea
- May slightly affect endurance measures in individual studies
Adverse effects and limitations
- Oral bioavailability is low: a significant part is destroyed in the liver and intestine
- Inferior to citrulline and dietary nitrates in effectiveness — when choosing, it is more logical to take those
- Often causes stomach upset and diarrhea at doses from 6–10 g
- May lower blood pressure and interact with antihypertensive drugs
Interactions
- With antihypertensives, nitrates and PDE5 inhibitors — risk of pronounced hypotension
- With citrulline — a shared metabolic pathway, taking them together duplicates the effect
- With lysine — they compete for transport, lysine may reduce arginine availability
Who must not use it
- Under 18 years: There are no data on supplement use by children and adolescents; as part of protein it is safe
- Pregnancy and lactation: There are no data on the safety of high doses in pregnancy and lactation
- Hypotension and taking antihypertensive drugs - caution
- After myocardial infarction — high doses are not recommended without a doctor
- Active herpes infection — a possible triggering effect
- Asthma — data on possible worsening of control are ambiguous
Sources
- Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials · d'Unienville NMA, Blake HT, Coates AM · Journal of the International Society of Sports Nutrition, 2021 · PMID 34965876
- A critical review of citrulline malate supplementation and exercise performance · Gough LA, Sparks SA, McNaughton LR · European journal of applied physiology, 2021 · PMID 34417881
See also
Comparisons
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