“Functional drinks and supplements that claim to enhance athletic performance are popular among both recreational and elite athletes,” wrote the team of South Korean researchers in the journal Nutrients. “However, athletes should only consume products that are scientifically proven to be effective.”
To assess the uses and limitations of these supplements, the researchers collected relevant, English-language randomized controlled trials, systematic reviews and meta-analyses from the PubMed, MEDLINE and Scopus databases from Jan. 1, 2010 to Nov. 10, 2022. The review covered a range of outcomes, including endothelial function, blood pressure, athletic performance and muscle soreness.
Arginine and Citrulline
L-Arginine (Arg) and L-Citrulline (Cit) are amino acids (obtained from dietary sources or produced endogenously) that contribute to the production of nitric oxide (NO) in the body and the removal of waste products during exercise. They are among the most used nutritional supplements for health promotion and athletic performance, the review puts forth, in a global market for nutritional supplements projected to reach $327.4 billion by 2030.
“Over the past decade, Arginine (Ar), Citrulline (Cit), and Citrulline Malate (CitMal) supplements have received considerable attention from researchers in the field of exercise nutrition, who have investigated their potential effects on hemodynamic function, endothelial function, aerobic and anaerobic capacity, strength, power and endurance,” the researchers noted.
Nitric oxide acts on a variety of physiological processes including vasodilation, mitochondrial respiration, glucose absorption and muscle contraction to improve these factors that influence exercise performance and skeletal muscle health.
“The results showed that both recreational and trained athletes did not see improved physical performance or increased nitric oxide (NO) synthesis with 0.075 g or 6 g doses of Arg supplement per body weight,” the researchers wrote.
“However, 2.4 to 6 g of Cit per day for 7 to 16 days of various nutritional supplements had a positive impact, increasing NO synthesis, enhancing athletic performance indicators, and reducing feelings of exertion. The effects of an 8 g acute dose of CitMal supplement were inconsistent, and more research is needed to determine its impact on muscle endurance performance.”
The review also noted that recent research has shown that exercise in itself can have a positive effect on the composition of gut microbiota, leading to improved gut health, a stronger immune system and better overall health outcomes.
“Based on the positive effects reported in previous studies, further testing is warranted in various populations that may benefit from nutritional supplements, including aerobic and anaerobic athletes, resistance-trained individuals, elderly people and clinical populations, to determine the impact of different doses, timing of ingestion and long-term and acute effects of Arg, Cit and CitMal supplements on cardiovascular health and athletic performance,” the review concluded.
Source: Nutrients 2023, 15(5), 1268
“Dietary Arginine and Citrulline Supplements for Cardiovascular Health and Athletic Performance: A Narrative Review”
Authors: Hun-Young Park et al.