Taking L-citrulline pills for 10 days at a specific dose doesn’t seem to make healthy young adults feel sick—only a few people might get a little stomach upset.

Taking a specific dose of L-citrulline for 10 days doesn’t change how your body uses sugar or handles lactic acid when you bike really hard, so it doesn’t help or hurt your energy or fatigue during intense exercise.

Taking a specific amino acid supplement called L-citrulline every day for a week, then taking one more dose an hour before a short, intense bike ride, helps trained male cyclists finish the ride 1.5% faster.

Taking a specific dose of L-citrulline for 10 days doesn’t make you bike harder, faster, or feel less tired—even though some people think it might help. Your heart, lungs, and muscles act the same as if you didn’t take it.

Taking at least 6 grams of L-citrulline every day might lower your bottom blood pressure number by about 3 points, but taking less than that doesn’t seem to do anything noticeable.

Taking L-citrulline supplements every day for a few weeks might slightly lower your blood pressure—like a small drop that could help keep your heart healthier.