L-arginine and L-citrulline are amino acids that have a wide range of effects on your body. Both of these protein building blocks can be found naturally in foods and synthesized in your body from other sources. In fact, citrulline can be produced in your body from arginine. Arginine and citrulline can be taken as nutritional supplements for their potential health benefits and low toxicity, although some side effects have been associated with arginine use. Talk to your doctor before using these compounds to make sure they are safe for you to consume.
Arginine is naturally found in nuts, seeds, cereals, corn, meat, and a variety of other food products. According to the Mayo Clinic, there is little evidence for a standardized dose or arginine because many different doses have been studied. A common dose of arginine supplements range between 2 to 3 g three times a day for a total of 6 to 12 g daily. In certain clinical settings, up to 20 g of arginine per day have been used to successfully treat symptoms of congestive heart failure.
According to MedlinePlus, a website sponsored by the National Library of Medicine, arginine supplementation is possibly safe for most people when taken in the short-term, however, side effects such as stomach pain, bloating, diarrhea, gout, blood abnormalities, allergies, inflammation, asthma, and low blood pressure have been reported. Not enough information is available regarding the safety of arginine supplementation on adolescents and pregnant or lactating women, therefore the use of arginine in these populations is not advised.
Citrulline is found most abundantly in nature in watermelons, but is also derived from the metabolism of arginine in your body. Little peer-reviewed scientific information regarding effective dosages of citrulline are available. However, a 2008 study published by the "British Journal of Nutrition" found that short-term supplementation of citrulline in 2 to 15 g doses is safe and well-tolerated. Another study published in 2002 by the "British Journal of Sports Medicine" found that 6 g per day of citrulline supplementation promoted aerobic energy production and changes in muscle metabolism in healthy subjects during exercise.
According to the book, "Nutritional Supplements in Sports and Exercise;" arginine and citrulline work together since arginine promotes the natural production of citrulline in your body. A high intake of arginine causes an increase in blood levels of citrulline as well, possibly making citrulline supplementation unnecessary if you are taking arginine supplements. However, not enough is known about the exact relationship between arginine and citrulline to determine the proper dosage of citrulline while also taking arginine.