L-arginine

Precautions

After a heart attack: in the VINTAGE MI trial (3 g three times a day for 6 months), 6 patients on L-arginine died (8.6%), none on placebo; the trial was stopped and the authors advise against L-arginine after a heart attack. Peripheral artery disease of the legs: in 133 patients who limp when walking, 3 g per day for 6 months resulted in less walking distance gained than placebo (11.5% vs 28.3%). Inflammation: CRP increased in those over 60, in people whose CRP was already high, and in cancer patients. Adverse effects: digestive and cardiovascular disorders reported in the short term, according to a review conducted for the US military. With an erectile dysfunction drug (PDE5 inhibitors): the combination was tested without a clear increase in adverse effects, but only in 373 patients followed by a doctor. Limits: strength and recovery: no effect on strength or nitric oxide (6 g before exercise, 12 trained men), nor on recovery after a heavy session (20 young adults), nor on muscular endurance (16 trained young men). Hormones: growth hormone even increased less after the session with L-arginine in 14 trained men, and IGF-1 did not budge across 9 studies. Blood glucose: no effect on fasting blood glucose, insulin, HbA1c or HOMA-IR across twelve trials. Vessels: no clear improvement in artery wall function in heart or metabolic disease patients, and no effect on mortality after a heart attack (927 patients). Performance studies contradict each other: the positive meta-analysis groups participants of all levels, sexes and ages, with very dispersed results for endurance, and a 2016 review concludes that L-arginine alone improves performance or recovery very little, based on small studies at risk of bias.