Safety of dietary supplementation with arginine in adult humans
Previous studies with animals and humans have shown beneficial effects of dietary supplementation with l-arginine (Arg) on reducing white fat and improving health. At present, a long-term safe level of Arg administration to adult humans is unknown. The objective of this study was to conduct a randomized, placebo-controlled, clinical trial to evaluate the safety and tolerability of oral Arg in overweight or obese but otherwise healthy adults with a body mass index of ≥ 25 kg/m2. A total of 142 subjects completed a 7-day wash-in period using a 12 g Arg/day dose. All the remaining eligible 101 subjects who tolerated the wash-in dose (45 men and 56 women) were assigned randomly to ingest 0, 15 or 30 g Arg (as pharmaceutical-grade Arg-HCl) per day for 90 days. Arg was taken daily in at least two divided doses by mixing with a flavored beverage. At Days 0 and 90, blood pressures of study subjects were recorded, their physical examinations were performed, and their blood and 24-h urine samples were obtained to measure: (1) serum concentrations of amino acids, glucose, fatty acids, and related metabolites; and (2) renal, hepatic, endocrine and metabolic parameters. Our results indicate that the serum concentration of Arg in men or women increased (P < 0.05) progressively with increasing oral Arg doses from 0 to 30 g/day. Dietary supplementation with 30 g Arg/day reduced (P < 0.05) systolic blood pressure and serum glucose concentration in females, as well as serum concentrations of free fatty acids in both males and females. Based on physiological and biochemical variables, study subjects tolerated oral administration of 15 and 30 g Arg/day without adverse events. We conclude that a long-term safe level of dietary Arg supplementation is at least 30 g/day in adult humans.
KeywordsArginine Health Nutrition Obesity Safety Supplementation
Body mass index
Observed safe level
Thyroid stimulating hormone
We thank staff nurses at Baylor Scott & White Hospital, as well as Gilson D. Honvoh, Shengdi Hu, Katherine Kelly, Faqiang Liu, Yuanyuan Luan, Gayan I. Nawaratna, and Tapasree R. Sarkar for assistance in this study. This work was supported by a grant from International Council of Amino Acid Science (Brussels, Belgium).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This study was approved by Baylor Scott & White Hospital and Texas A&M University Institutional Review Boards.
Informed consent was obtained from all study subjects.
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