Taking a specific amino acid supplement called L-arginine every day for three weeks helps people who’ve had a heart attack and are in rehab walk farther in six minutes than those who take a sugar pill.

Taking a specific amino acid supplement called L-arginine every day for three weeks might make people feel less tired when they exercise, after having a heart attack and while doing heart rehab — compared to taking a sugar pill.

Taking a daily L-arginine supplement for two weeks doesn't make healthy young men cycle any harder or faster in a short, self-paced test compared to taking a sugar pill.

Taking L-arginine while doing heart rehab after a heart attack might help you feel stronger and move better, no matter how old you are, your gender, how fit you were before, or other health problems you have.

Taking a daily L-arginine supplement for two weeks doesn't help lower ammonia levels in the blood when healthy young men cycle hard, because the supplement group and the placebo group ended up with pretty much the same ammonia levels.

Taking L-arginine pills in these amounts doesn’t raise the levels of L-arginine or related molecules in your blood or urine, because your body breaks them down too quickly before they can get into your system.