L-arginine is an amino acid your body uses to produce nitric oxide, a molecule that relaxes and widens blood vessels. This single function drives most of its benefits: better blood flow means lower blood pressure, improved exercise performance, faster wound healing, and stronger erections. Your body makes some L-arginine on its own and you get more from food, but supplemental doses (typically 3 to 6 grams per day) are where the more pronounced effects show up.
How L-Arginine Works in the Body
Enzymes in your cells convert L-arginine into nitric oxide and a byproduct called L-citrulline. Nitric oxide signals the smooth muscle lining your blood vessels to relax, which widens the vessels and lets blood flow more freely. This improved circulation is the mechanism behind nearly every benefit associated with L-arginine. When your L-arginine levels are adequate, your body can produce enough nitric oxide to keep blood vessels flexible and responsive. When levels are low, or when demand is high (during intense exercise, recovery from surgery, or in people with vascular problems), supplementation can make a measurable difference.
Blood Pressure Reduction
L-arginine supplementation lowers blood pressure by about 5.4 mmHg systolic and 2.7 mmHg diastolic, based on pooled data from clinical trials. That reduction is comparable to what you’d get from dietary changes or starting a regular exercise program. For someone with borderline or mildly elevated blood pressure, that drop could be enough to move readings back into a healthier range. It won’t replace medication for someone with significantly high blood pressure, but it can be a meaningful addition to lifestyle strategies.
Erectile Dysfunction
Because erections depend heavily on blood flow, L-arginine’s effect on nitric oxide production translates directly to sexual health. A meta-analysis of 10 randomized trials found that daily doses ranging from 2.8 to 8 grams significantly improved mild to moderate erectile dysfunction compared to placebo. In one double-blind trial, men with blood-flow-related ED took 6 grams daily for three months. By the end, 74% had improved by at least one severity category. The strongest results appeared in men who started with milder problems: 24% of participants reached scores consistent with no ED at all. The effect builds over weeks, not days, so this isn’t a quick fix but rather a gradual improvement in vascular function.
Exercise and Athletic Performance
L-arginine can boost both aerobic and anaerobic performance, though the effects are modest. A systematic review and meta-analysis found a large, statistically significant improvement in aerobic performance, with athletes showing longer time to exhaustion, higher power output during cycling time trials, and better scores on standardized endurance tests. The anaerobic side showed a smaller but still significant benefit, including improvements in peak power, upper body strength, and total repetitions on bodyweight exercises like chin-ups.
The doses that produced these results ranged from 6 to 10 grams per day, often taken acutely (within a few hours of exercise) or over short supplementation periods of less than a week. The benefits appear most clearly during moderate to submaximal exercise, the kind of sustained effort involved in distance cycling, running, or circuit training, rather than single explosive movements.
Wound Healing and Post-Surgery Recovery
L-arginine plays a direct role in collagen production, the protein that forms the structural framework of healing tissue. In a study of healthy older adults, 17 grams of supplemental arginine daily for two weeks significantly increased collagen accumulation in experimental wounds compared to placebo. The amino acid didn’t speed up skin resurfacing, but it strengthened the underlying repair.
The surgical recovery data is especially striking. In cancer patients recovering from oral or laryngeal surgery, an arginine-enriched formula cut fistula formation from 17.6% to 5.2% and shortened hospital stays from 36 days to 24 days. Patients recovering from stomach cancer surgery who received arginine-containing nutrition had zero wound healing complications compared to 26.7% in the control group. A broader review of 13 randomized trials covering over 1,200 surgical patients found that arginine-enriched nutrition cut postoperative infection rates by more than half and reduced hospital stays by about 3.5 days, with no serious side effects.
Top Food Sources
The average diet provides roughly 3.6 to 4.9 grams of L-arginine daily, but some foods are especially rich. Per 100 grams:
- Soy protein isolate: 6.7 g
- Pumpkin and squash seeds: 5.4 g
- Watermelon seeds: 4.9 g
- Sesame seeds: 3.3 g
- Peanuts: 3.25 g
- Soybeans: 3.15 g
- Peanut butter: 2.7 g
- Tahini: 2.68 g
Seeds and legumes dominate the list. A handful of pumpkin seeds as a snack or a couple of tablespoons of peanut butter can contribute a meaningful amount, though reaching the 6-gram-plus doses used in clinical trials typically requires supplementation.
Dosage and Safety
Most clinical trials use doses between 3 and 6 grams per day, split across two or three servings taken with meals. For erectile dysfunction specifically, 6 grams daily for at least three months appears to be the effective range. For blood pressure and exercise, lower doses in the 3 to 6 gram range have shown results.
The no-observed-adverse-effect level for L-arginine has been set at 30 grams per day, meaning that even very high doses have been well tolerated in studies tracking blood pressure, kidney function, liver function, and metabolic markers. That said, the most commonly reported issues at supplemental doses are digestive discomfort and, in rare cases, skin reactions. People with a history of herpes simplex outbreaks sometimes avoid L-arginine because the virus uses it to replicate, though clinical evidence on this is mixed. L-arginine has also shown inconsistent effects in people with dangerously high blood pressure, lowering it in some cases but not in others, so it’s not a reliable tool for severe hypertension.