What L-Arginine is
L-arginine is an amino acid found in many protein-rich foods such as meat, poultry, fish, dairy, and nuts; the body also makes some of its own (mainly in the kidneys, from citrulline). A portion of the arginine you consume can be converted into nitric oxide, a compound that relaxes and widens blood vessels, which is the main reason it is marketed as a dietary supplement.
Commonly used for
Taken by athletes and exercisers in hopes of boosting blood flowUsed in an attempt to improve exercise or athletic performanceUsed in an attempt to build muscle or aid recovery after workoutsMarketed as a "nitric oxide booster" in pre-workout and bodybuilding products
What the evidence shows
According to the NIH Office of Dietary Supplements, the research supporting supplemental arginine as a performance enhancer is "limited and conflicting," and a review of 54 studies concluded it provided "little or no enhancement of athletic performance" and did not improve recovery from exhaustion. The NIH also notes that doses of roughly 2-20 g/day have shown little to no effect on anaerobic or aerobic exercise, and typically no effect on nitric oxide levels, blood flow, or exercise metabolites in trained athletes. NCCIH likewise states there is "no clear evidence" that arginine and similar bodybuilding or performance supplements improve athletic performance. Overall, its claimed ability to increase strength, improve performance, or speed muscular recovery has little scientific support.
Typical dosage
There is no established supplement dose, since benefits are not well supported. In research summarized by the NIH, intakes of up to about 9 grams per day for several days or weeks are generally reported as safe and well tolerated, while higher amounts (roughly 9-30 g/day) more often cause side effects. The safety of high-dose arginine taken for longer than 3 months is not known. Talk to your doctor or pharmacist before using L-arginine, especially if you have a medical condition, take any medications, or are pregnant or breastfeeding.
Safety
At moderate doses (up to about 9 g/day for several days or weeks) the NIH reports arginine is generally safe and well tolerated, but the long-term safety of high doses beyond about 3 months is not known. NCCIH also warns that bodybuilding and performance products in general are sometimes adulterated with hidden prescription drugs or anabolic steroids, and that such products have become a leading cause of supplement-linked liver injury, so choose products carefully and consult a clinician.
Side effects
The NIH reports that at higher intakes (about 9-30 g/day) the most commonly reported adverse effects are gastrointestinal complaints such as diarrhea and nausea, along with a slight drop in blood pressure. The effects of very high or long-term use are not well characterized.
Interactions & cautions
No specific drug interaction for L-arginine is established in the cited NIH sources. However, because arginine can slightly lower blood pressure and acts on blood vessels, and because NCCIH cautions that dietary supplements can interact with medications or other supplements, extra care is reasonable if you take blood-pressure medicines or other drugs that affect blood vessels or nitric oxide. Tell your healthcare provider about all supplements and medicines you take so they can check for possible interactions.
This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Summarized from public health authorities; general reference, not medical advice. Talk to a licensed healthcare professional before starting any supplement.