Acute Effect of L-Arginine Supplementation on Fat and Carbohydrate Metabolism Before, During, and After Endurance Exercise in Athletes
In today’s societies, supplement consumption is practiced in various ways, and it is believed that supplements can improve athletic performance, leading to better movement execution during both training and competition. Generally, supplements are categorized into three groups: nutritional (vitamins, amino acids, carbohydrates, proteins), performance enhancers (caffeine, creatine, L-carnitine), and doping (nutritional supplements aimed at enhancing physical strength). Among the various amino acids, the effect of L-arginine supplementation on athletic performance or recovery quality improvement is of particular interest.
L-Arginine According to research, L-arginine plays a cellular signaling role in tissues. In fact, arginine is a semi-essential amino acid and a precursor for nitric oxide production, leading to vasodilation. This process facilitates blood flow to the organs engaged in physical activity, enhancing the athlete’s performance, particularly in aerobic activities. In healthy adults with normal protein consumption, endogenous synthesis of L-arginine is usually sufficient to meet physiological needs. However, during intense exercise, the body’s endogenous production may not be enough; therefore, L-arginine is considered a semi-essential or conditionally essential amino acid.
L-Arginine Use The use of L-arginine supplementation is common among athletes, and it is marketed as a nitric oxide booster aimed at increasing power and endurance. Researchers studied the impact of L-arginine supplementation on the metabolic response after exercise in twelve male judokas. They showed that this supplement can increase glucose and insulin concentrations and decrease free fatty acids (FFAs) during the recovery phase.
Effects of L-Arginine In a study by McConnell, the impact of L-arginine supplementation on exercise metabolism was examined, and the results showed that the supplement improved endothelial function and increased plasma insulin, growth hormone, glucagon, catecholamines, and prolactin at rest. Nascimento and colleagues also studied the effects of L-arginine supplementation and acute resistance exercise on blood lipid profiles and inflammatory proteins in overweight men. The results showed no significant changes in triglycerides, total cholesterol, adiponectin levels, or time-dependent changes under various conditions.
Based on existing literature, it appears that L-arginine supplementation can cause vascular changes via nitric oxide. However, its specific effects on metabolism cannot be definitively stated, and since research on the availability of L-arginine during and after exercise is limited, further studies are needed.
L-Arginine Implications This line of research seems to have important implications for fat and carbohydrate metabolism during exercise. Therefore, the current study aimed to investigate the acute effects of L-arginine supplementation on fat and carbohydrate metabolism before, during, and after endurance exercise, as well as its potential impact on athletic performance.
Study The present study investigated the acute effects of L-arginine supplementation on fat and carbohydrate metabolism before, during, and after endurance exercise. The results showed that acute L-arginine supplementation increased maximum oxygen consumption (VO2max), maximum heart rate, and prolonged the time to exhaustion during progressive exercise. However, the mechanisms through which L-arginine supplementation affects performance are not fully understood. Therefore, the study also examined the effect of acute L-arginine supplementation on VO2max, heart rate, and time to exhaustion during progressive exercise.
The results aligned with those of Majzoub and colleagues, who investigated the effects of a one-week L-arginine supplementation on respiratory gases and lactate levels in female handball players. They reported that one week of supplementation increased VO2max.
Research Process They attributed this increase to nitric oxide-induced vasodilation, suggesting that interventions affecting nitric oxide bioavailability can alter oxygen cost, influence blood flow, and improve nutrient delivery while assisting in the removal of metabolic waste products. Researchers also found that L-arginine supplementation increased carbohydrate metabolism following high-intensity interval training in overweight individuals. The underlying mechanisms may include increased GLUT-4 expression in muscle tissue, activation of AMPK, and glucagon release induced by L-arginine supplementation, which can generally increase carbohydrate metabolism during exercise compared to pre-exercise levels.
Research Methodology Catecholamines, glucagon, and cortisol are secreted more during high-intensity endurance exercise than during other types of training, positively affecting glycolysis and glycogenolysis, thus increasing carbohydrate metabolism. L-arginine supplementation activates glycolysis and glycogenolysis due to increased GLUT-4, AMPK, and glucagon levels, leading to a significant increase in carbohydrate metabolism post-exercise. Additionally, the increased heart rate at exhaustion, prolonged exercise duration, higher VO2max, and enhanced carbohydrate metabolism suggest that acute L-arginine supplementation helps the body experience a higher aerobic capacity, necessitating a higher maximum heart rate.
L-Arginine Supplementation Impact L-arginine supplementation increases functional factors such as VO2max, time to exhaustion, and glucose metabolism. Since the respiratory exchange ratio is influenced by the balance of fat and carbohydrate metabolism, it is not surprising that L-arginine supplementation may elevate this ratio.
Acute L-arginine supplementation did not affect blood glycerol levels before progressive exercise but did increase glycerol levels during and after progressive exercise. These findings are consistent with those of Forbes and colleagues, who showed that one dose of L-arginine increased glycerol levels following acute cycling exercise, a key marker of lipolysis.
Nascimento’s Research Nascimento and colleagues also found that one session of L-arginine supplementation after acute resistance exercise reduced non-esterified fatty acid levels one hour post-exercise during recovery, indicating an increase in fat oxidation. However, their results are in contrast to the current study, which found no such reduction in glycerol levels. Researchers attributed the reduction in glycerol during exercise to elevated nitric oxide levels and catecholamine stimulation, which inhibited lipolysis. However, there is no definitive evidence that L-arginine directly inhibits lipolysis.
Conclusion The current study found that acute L-arginine supplementation increased VO2max, heart rate, and time to exhaustion during progressive exercise. It also increased maximum carbohydrate oxidation, respiratory exchange ratio, and glycerol and glucose concentrations post-exercise. Since L-arginine supplementation was shown to enhance VO2max and time to exhaustion, it is suggested that athletes use L-arginine to enhance aerobic capacity, improve endurance performance, and reduce fatigue during aerobic training. This study aimed to investigate the effects of L-arginine supplementation on carbohydrate and fat oxidation and certain cardiovascular-respiratory factors during progressive exercise.
Benefits of L-Arginine Supplementation Overall, L-arginine supplementation reduced carbohydrate oxidation and increased fat oxidation during and after progressive exercise. It also increased VO2max and heart rate. However, due to limited data, caution is advised in explaining these mechanisms, and further research is necessary.