Norvaline is a chemical compound that is an isomer of valine, one of the branched-chain amino acids. It has gained attention as an ingredient in dietary supplements, often marketed for athletic performance. Its inclusion stems from its distinct biochemical properties.
How Norvaline Interacts with the Body
Norvaline’s primary interaction with the body involves its function as an arginase inhibitor. Arginase is an enzyme that breaks down L-arginine into L-ornithine and urea as part of the urea cycle. By inhibiting this enzyme, norvaline helps maintain higher levels of L-arginine.
L-arginine serves as a precursor for nitric oxide (NO) synthesis, a molecule involved in various physiological processes. When arginase activity is reduced by norvaline, more L-arginine becomes available for nitric oxide synthase (NOS) enzymes to convert into nitric oxide. This mechanism indirectly increases nitric oxide production.
Use in Athletic and Bodybuilding Supplements
Supplement manufacturers include norvaline in their products to support nitric oxide pathways. Increased nitric oxide production can lead to vasodilation, the widening of blood vessels. This effect is often sought by athletes and bodybuilders for the “muscle pump” sensation during exercise.
Enhanced vasodilation is theorized to improve blood flow to working muscles. This increased blood flow could facilitate better delivery of oxygen and nutrients to muscle tissue during intense physical activity. Additionally, it may aid in the efficient removal of metabolic waste products, such as lactate and ammonia, which accumulate during exercise and can contribute to fatigue.
Research on Norvaline’s Safety
Research has explored norvaline’s safety profile, with some studies raising concerns, particularly in laboratory settings. A 2019 Toxicology In Vitro study by Kate Samardzic and Kenneth J. Rodgers reported on the cytotoxicity and mitochondrial dysfunction caused by L-norvaline. This study found norvaline could induce cellular damage and be cytotoxic to SH-SY5Y human neuroblastoma cells (a type of brain cell) at concentrations above 125 µM.
These findings were from in vitro (test tube) experiments, not human trials. The concentrations of norvaline used were significantly higher than what would typically be found in the human body from supplement use. For instance, typical athlete doses of 200-300 mg/day result in brain concentrations far below the cytotoxic levels observed in vitro. While some suggest toxicity reports may be overstated, long-term human safety data for norvaline is limited.
Common Dosages and Forms
Norvaline is almost always found in multi-component dietary supplements, not as a standalone product. It is a common component in pre-workout formulas and nitric oxide-boosting supplements. Typical serving sizes generally range from 100 mg to 300 mg.
Some sources suggest dosages of 200 to 400 mg per day. It is frequently included in proprietary blends, meaning the exact amount per serving may not always be explicitly listed. Due to ongoing research and limited human safety data, no official Tolerable Upper Intake Level (UL) or universally recommended dosage exists.