Arginine, an essential α-amino acid, is used in the biosynthesis of proteins, increases blood flow, growth hormone (GH), improves memory, boosts immunity, detoxifies ammonia, and is involved in formation of creatine, agmatine, glutamate, polyamines (essential for muscle regeneration and growth), ornithine, and citrulline (R, R). etc…
About 60% of the absorbed l-arginine is metabolized by the gastrointestinal tract, and only 40% reaches the systemic circulation intact, which is not very effective for increasing arginine levels in the blood. (R, R) Plus high dose, 9g+ can cause quite some stomach upset.
However, it’s far from ineffective, let’s have a look.
Arginine boosts Growth hormone
Oral supplementation of arginine at doses ranging between 5-9g increases resting GH. The GH response increase in a dose-dependent manner and there is no further benefit past 9g. Most studies using oral arginine have shown that arginine alone increases the resting growth hormone levels at least 100%, while exercise can increase growth hormone levels by 300-500%. However, the combination of oral arginine plus exercise attenuates the growth hormone response, and only increases growth hormone levels by around 200% compared to resting levels. (R, R)
A significant increase in GH and IGF-1 and a decrease in IGFBP3 was seen after 3 weeks of arginine and ornithine supplementation. (R)
It’s also shown that 1.2 to 1.5g of lysine with arginine each are able to increase growth hormone by 8 and 2.7 fold respectively, but there was no rise in GH when either one was administered alone. (R, R)
Arginine helps Burn Fat
Arginine is able to improve oxidative metabolism, by increasing the body’s efficiency at transporting and utilization of fatty acids and glucose (glycolysis).
Arginine stimulates lipolysis and the expression of key genes responsible for activation of fatty acid oxidation to CO2 and water. It also prevents fatty acid synthesis from glucose by downregulating the enzymes malonyl-CoA decarboxylase (MCD), fatty acid synthase (FAS) and stearoyl coenzyme-A desaturase-1 (SCD1) in the liver.
Arginine upregulates enzymes that transport fatty acids (HSL, CPT1), increases mitochondria biogenesis (PCG-1alpha), improves insulin sensitivity, stimulates the growth of brown adipose tissue and reduces white adipose tissue. This leads to a great number of mitochondria, higher energy expenditure and thermogenesis and ultimately fat loss. (R)
Arginine enhances Muscle protein synthesis & wound healing
Arginine activates the mTOR cell signaling pathway in skeletal muscle to enhances protein synthesis and whole-body growth (R). There is also indirect evidence that Arg inhibits proteolysis (protein breakdown) in skeletal muscle (R).
Arginine prevents the oxidation of BCAAs (which stimulate muscle protein synthesis and hypertrophy), thus ensuring that maximal leucine availability for the hypertrophy response.
Without arginine, testosterone cannot perform its anabolic functions in mice (R).
Human studies have concluded that Arg supplementation enhances hydroxyproline and ornithine content and tensile strength in wound tissues via a proline-dependent mechanism (R). Also, due to enhanced blood flow, arginine aids in supplying more oxygen and nutrients to the wound/tissue that needs growth and repair.
Arginine improves Exercise performance
Arg improves exercise performance and prolongs time to exhaustion by detoxifying ammonia (reduces it to urea via the urea cycle) and reduces lactate production.
Nitric oxide, synthesized by arginine, is responsible for mediating satellite cells activation, which stimulates muscle protein synthesis and repair, and can be very beneficial for reducing DOMS. (R)
However, it would seem that it has less benefit on trained men than for untrained men. (R)
Arg in combination with BCAA is beneficial for improving exercise performance of repeated sprints on consecutive days, preventing performance declines. As a side note, BCAAs also prevents tryptophan uptake in the brain (reducing serotonin), and arginine prevents BCAA oxidation, (R) making it a potent potential dopamine boosting ingredient. Just use phenylalanine and/or tyrosine with this combo.
I don’t think everyone should take Arginine
Certain conditions (increased endotoxins, gene mutations, etc) can increase nitric oxide production from arginine to excessive levels, which have been associated with:
- tumor promoting
- higher mortality. (R, R)
- herpes virus (are able to let it resurface) (use lysine to counter this)
- increases prolactin (independent of NO) (R). More on lowering prolactin here…
- Intestinal inflammation
- enhanced COX activity which increases prostaglandin E2 (PGE2) production and therefore increases cortisol, inflammation, etc… (R).
Arginine can be used pre-workout to boost blood flow and also before bed to spike growth hormone. Arginine pairs synergistically with lysine to boost GH during sleep. Just make sure that the ratio of arginine:lysine doesn’t exceed 1.5:1 as the two needs to be in balance.