What is L-Arginine?
L-arginine is an essential amino acid that contributes significantly to wound healing, detoxification, and immune functions. It also aids in the secretion of various hormones such as glucagon, insulin, and growth hormone.
One of L-arginine's crucial roles is in the production of nitric oxide, a compound that helps regulate blood vessel tone. Nitric oxide relaxes blood vessels, thereby enhancing blood flow.
While L-arginine is often taken as a sports supplement to promote cardiovascular health, human studies have not consistently shown significant benefits, even with doses exceeding 3 grams per day.
L-Arginine Food Sources
L-arginine is naturally present in many foods, including nuts, seeds, meat, seafood, and soy. Typically, the body produces sufficient L-arginine, but sometimes additional supplementation is necessary to meet the body's needs.
What is L-Citrulline?
L-citrulline is an amino acid known for its role as a precursor to L-arginine. It is primarily found in watermelon and is converted to L-arginine in the body.
Supplementing with L-citrulline has proven more effective than L-arginine in raising the body's L-arginine levels. Consequently, L-citrulline has gained popularity as a sports supplement and is often included in combination products.
Fitness Benefits
Studies have shown that L-arginine supplementation can influence growth hormone production, blood flow, mitochondrial function, and energy metabolism, which could benefit athletes. However, human clinical trials have generally shown minimal benefits in improving physical performance with L-arginine supplementation. In contrast, L-citrulline has demonstrated positive results in numerous double-blind human studies.
These studies suggest that a typical dosage of 2.4 to 6 grams of L-citrulline daily may enhance strength, power, and endurance during high-intensity resistance exercises. This improvement is significant because exercising to the point of muscle failure, where you cannot complete another repetition, is considered the most effective way to stimulate muscle growth. L-citrulline's ability to increase the number of repetitions before reaching muscle failure is a valuable benefit.
While not all research on L-citrulline in sports medicine shows positive outcomes, several reviews have concluded that it significantly enhances high-intensity strength and power performance. L-citrulline supplementation has also been found to reduce muscle soreness after weight training, although it does not improve aerobic exercise endurance.
Effects on Growth Hormone Secretion
L-arginine is often used to promote the secretion of growth hormone by the pituitary gland, which is crucial for muscle and skeletal growth. Bodybuilders frequently use L-arginine supplements to boost natural growth hormone levels. While L-arginine can increase growth hormone output, especially when administered intravenously, its effectiveness as a supplement varies.
L-arginine supplementation (10 grams per day) has shown a slight increase in growth hormone secretion in younger adult males but does not appear to enhance growth hormone release in older individuals. Similarly, even at high doses, L-citrulline has not been shown to raise growth hormone levels in healthy males.
Cardiovascular Support
L-arginine is known to support heart and blood vessel health. By boosting nitric oxide levels, L-arginine improves blood flow, reduces blood clot formation, and enhances blood fluidity, making it flow more easily through blood vessels.
However, L-citrulline has shown superior results in human clinical trials. Studies indicate that L-citrulline or watermelon extracts are more effective than L-arginine in supporting blood pressure control and restoring blood vessel wall flexibility.
Key Takeaways
L-arginine and L-citrulline are amino acids important for health and performance. L-arginine supports wound healing, hormone secretion, and blood vessel function by increasing nitric oxide levels, although its benefits in human studies are inconsistent. It's found in nuts, seeds, meat, and seafood but may require supplementation in some cases. L-citrulline, primarily from watermelon, converts more efficiently to L-arginine in the body and has shown superior results in enhancing physical performance and cardiovascular health, particularly in supporting blood pressure control and restoring blood vessel flexibility.
These findings underscore L-citrulline's potential as a preferred supplement for improving athletic performance and cardiovascular function.