Arginine

What is arginine and what does it do in the body?

Arginine is an amino acid found in protein-rich foods, especially animal products and nuts; the body also makes it from citrulline, mostly in the kidneys. According to NIH ODS, typical dietary intake is 4–5 grams per day. ^[1] It is the main precursor in nitric oxide synthesis (via NOS enzymes); nitric oxide plays a role in areas such as vasodilation, blood flow, mitochondrial respiration, and platelet function. ^[2]

Supplement marketing rests on this mechanism: if nitric oxide rises, oxygen and nutrient delivery to muscles increases, fatigue products such as lactate and ammonia are cleared faster, and creatine synthesis and growth hormone secretion are supported. NIH ODS reports these four views as “suggested by some experts.” ^[1] A plausible mechanism does not mean that orally taken arginine changes outcomes; each claim is given below together with the measured result.

In a randomized, double-blind, placebo-controlled crossover study of 20 healthy volunteers (6 different dosing regimens), citrulline raised plasma arginine levels (AUC and Cmax) in a dose-dependent manner more effectively than arginine itself; the study’s introduction explains this by extensive presystemic elimination of oral arginine by intestinal arginase. No administration improved flow-mediated dilation (FMD) from baseline. ^[8]

Does arginine improve athletic performance?

According to NIH ODS, support for arginine as a performance enhancer is limited and conflicting; at doses in the 2–20 g/day range, little or no effect was seen on anaerobic or aerobic exercise. A review of 54 clinical trials concluded that in healthy, active adults arginine (usually given mixed with other ingredients) improved athletic performance little or not at all and did not improve recovery after exercise. Most studies have few participants, mostly men aged 18–25 (only four include women), and lasted 4–8 weeks; none lasted three months or longer. ^[1]

The 2020 systematic review by Viribay and colleagues covered 18 studies; 15 entered the meta-analysis. Pooled results were reported as an SMD of 0.84 (95% CI 0.12–1.56; I² 89%; p=0.02, “large”) in aerobic performance tests and 0.24 (95% CI 0.05–0.43; I² 0%; p=0.01, “small”) in anaerobic tests. ^[3] The very high heterogeneity in the aerobic result (I² 89%) and the wide CI make it hard to rely on a single number. A commentary published in Nutrients in 2025 argues that this meta-analysis made errors common in sports nutrition and that the pooled effect estimates are distorted. ^[4] The affiliation of one of the review’s authors appears in PubMed as a sports science and nutrition company. ^[3]

A 2012 review reports that training level is decisive: in untrained or moderately trained healthy people, nitric oxide precursors may improve aerobic and anaerobic exercise tolerance, whereas no performance effect is seen in highly trained people; most of the evidence comes from young men, and further studies are needed in older people and women. ^[2]

The growth hormone and IGF-1 claim

NIH ODS states that findings on the effect of supplemental arginine on growth hormone and IGF-1 levels are conflicting: depending on the study, participants’ age, fitness level, use of other supplements, and the nature of the exercise, growth hormone secretion has been both decreased and increased. An increased secretion has not been shown to translate into more blood flow to muscle or more protein synthesis. There is little evidence that arginine alone raises muscle creatine levels or is superior or complementary to direct creatine intake. ^[1]

Does arginine increase nitric oxide and blood flow?

According to NIH ODS, arginine generally did not affect nitric oxide levels, blood flow, or exercise metabolites such as lactate and ammonia, particularly when well-trained athletes (cyclists, tennis players, judo athletes) used it for 1–28 days. ^[1] In other words, “pump” labels mostly present a mechanistic assumption as performance evidence; the measured studies have not shown a consistent picture supporting this effect. An outcome measure (nitric oxide derivatives, FMD) is not at the same evidence level as a clinical or performance outcome.

Does arginine lower blood pressure?

The 2011 meta-analysis by Dong and colleagues pooled 11 randomized, double-blind, placebo-controlled trials (387 participants) of oral L-arginine at 4–24 g/day. Compared with placebo, systolic blood pressure fell by 5.39 mmHg (95% CI −8.54 to −2.25) and diastolic blood pressure by 2.66 mmHg (−3.77 to −1.54); sensitivity analyses of trials lasting at least 4 weeks and of trials in which participants were not taking blood pressure medication gave similar results. The inverse relationship between baseline systolic blood pressure and the reduction was not significant (p=0.13). ^[5]

The more recent 2022 review covered 22 RCTs (30 effect sizes) from oral arginine trials lasting ≥4 days: systolic blood pressure fell by 6.40 mmHg (95% CI −8.74 to −4.05) and diastolic blood pressure by 2.64 mmHg (−3.94 to −1.40). In subgroup analyses, the reduction was seen in both normotensive and hypertensive participants. At doses above 9 g/day there was no significant reduction (systolic −1.66 mmHg; 95% CI −4.36 to 1.03). The article’s abstract states that there was also no significant change in trials longer than 24 days or in obese individuals; however, in the subgroup table of the full text, the systolic reduction in trials longer than 24 days is significant at −5.26 mmHg (95% CI −7.66 to −2.87), and in obese individuals it is borderline (−7.93; 95% CI −15.87 to 0.001; p = 0.050). This inconsistency between the abstract and the table reduces the certainty of the result. ^[6] The size of the reductions is small, the trials are short, and no result on cardiovascular events is shown.

Is arginine safe to use after a heart attack?

VINTAGE MI is a single-center, randomized, double-blind, placebo-controlled trial: 153 patients with a first ST-elevation myocardial infarction (77 of them aged 60 and over) received arginine (target dose 3 g three times daily) or placebo for 6 months in addition to standard therapy. No significant differences between groups were seen in vascular stiffness measurements or in left ventricular ejection fraction. During the study, 6 participants (8.6%) in the arginine group died, and no deaths occurred in the placebo group (p=0.01); the data safety monitoring board therefore stopped enrollment. The authors stated that arginine added to standard post-infarction therapy did not improve vascular stiffness or ejection fraction, might be associated with a higher mortality rate, and should not be recommended after infarction. ^[7] Because death was not the primary endpoint, the certainty of the result is limited; even so, the safety of arginine in this group has not been supported.

Is arginine safe, and what are the side effects?

According to NIH ODS, most study results suggest that arginine up to 9 g per day for several days or weeks is safe and well tolerated. At doses of 9–30 g/day, the most commonly reported adverse events are digestive complaints such as diarrhea and nausea, and a mild fall in blood pressure. The safety of high-dose arginine supplementation used for longer than three months is unknown. ^[1]

Whether arginine’s effect adds to the effect of blood pressure–lowering medication in people taking such drugs has not been measured directly; because arginine lowers blood pressure, the possibility of an additional reduction is theoretical. ^{[5] [6]} In the blend formulas found in products, arginine is mostly combined with other ingredients; in that case it becomes unclear which ingredient accounts for the effect in a study. ^[1]

Which foods contain arginine, and what supplement forms exist?

Arginine is a natural component of protein-rich foods; NIH ODS lists animal products and nuts as the richest sources and gives typical intake as 4–5 g per day. ^[1] In supplements, L-arginine is found alone or mixed with other ingredients; the Türkiye list gives chemical synthesis and duck feathers as sources for L-arginine, and chemical synthesis for arginine alpha-ketoglutarate. ^[10] In blend formulas, it can remain unclear whether an effect in a study came from arginine or from another ingredient; the 54-study review reported by NIH ODS notes that arginine was mostly given together with other ingredients (such as BCAAs and lysine). ^[1]

How should this evidence be read?

The shared limitation of the performance studies is the participant profile: mostly men aged 18–25, 4–8 weeks, with duration not exceeding three months. ^[1] Blood pressure results, in turn, are a surrogate outcome; the effect of a small reduction on cardiovascular events was not measured in these studies. ^{[5] [6]} These two results do not contradict each other: a small reduction in blood pressure does not mean a performance gain or a clinical benefit. The post–heart attack study, on the other hand, is a single RCT in one specific patient group and cannot be generalized; but it shows that the assumption of arginine as a “harmless amino acid” does not hold in every clinical situation. ^[7]

Arginine supplements in Türkiye

For every dietary supplement to be placed on the market in Türkiye, approval from the Ministry of Agriculture and Forestry is mandatory; for imported products, applications can be made only to the Istanbul and Ankara Provincial Directorates. ^[9]

The Ministry’s Restricted Substances List for dietary supplements (last updated September 21, 2026) has an L-arginine row: the source is chemical synthesis or duck feathers; at most 1,200 mg/day for ages 4–10 and at most 5 g/day for ages 11 and over (for ages 11 and over, published March 8, 2016, updated September 27, 2017; for ages 4–10, January 23, 2017). Arginine alpha-ketoglutarate is a separate row: chemical synthesis, 5 g/day in the ages 11 and over column (June 16, 2017). ^[10]

These limits are not in the same context as the 4–24 g/day range used in the blood pressure meta-analyses: study doses belong to research conditions, not to a supplement product, and extend above the list’s upper limit. Likewise, NIH ODS’s summary “safe up to 9 g/day for several days or weeks” is not a benchmark for the approved product amount in Türkiye. ^{[1] [10]}

Who should be cautious?

• People who have had an acute myocardial infarction: Deaths were seen in the arginine group in VINTAGE MI, and the authors concluded that use after infarction should not be recommended. ^[7]
• People taking blood pressure–lowering medication and people with low blood pressure: A blood pressure–lowering effect was reported in the meta-analyses. ^{[5] [6]}
• Digestive complaints: At 9–30 g/day, diarrhea and nausea are the most commonly reported adverse events. ^[1]
• Ages 4–10: The Restricted Substances List sets a separate, lower limit for this age than for ages 11 and over. ^[10]

Evidence table: claim, population, and limits

This guide does not recommend personal doses or treatment; in situations such as cardiovascular disease, regular medication use, pregnancy, and breastfeeding, the decision depends on individual clinical assessment.