Hormonal response to L-arginine supplementation in physically active individuals

Area of Science:

• Exercise Physiology
• Nutritional Biochemistry
• Endocrinology

Background:

• Nutritional supplements containing L-arginine are theorized to boost exercise performance by elevating insulin and growth hormone (GH) levels.
• Investigating hormonal changes in response to L-arginine can elucidate its physiological effects on physical performance.

Purpose of the Study:

• To assess the impact of L-arginine supplementation on serum insulin, GH, IGF-1, and cortisol levels during exercise.
• To evaluate the effects of L-arginine on overall exercise performance.

Main Methods:

• Fifteen trained runners were assigned to either 6 g L-arginine (ARG) or placebo (PLA) groups.
• Blood samples were collected pre- and post-exercise sessions and during recovery.
• Exercise protocol involved two 5 km time-trial running tests.

Main Results:

• No significant differences were found in IGF-1, insulin, or running times between the ARG and PLA groups.
• While GH and cortisol levels increased post-exercise in both groups, L-arginine supplementation did not significantly alter these responses compared to placebo.

Conclusions:

• L-arginine supplementation did not stimulate insulin, GH, or IGF-1 production in trained runners.
• Supplementation with L-arginine provided no discernible benefits regarding hormonal response or exercise performance.