L-Arginine Benefits, Deficiency, Toxicity, and Food Sources
Arginine is an amino acid, which is one of the building blocks of proteins. It is an essential amino acid in children but nonessential in adults because infants bodies cannot produce enough of the compound in time to meet the metabolic demand.
It is classified as a semi-essential or conditionally essential amino acid because, under normal circumstances, the body can synthesize enough of it. However, in certain situations, such as illness or stress, the body may not produce enough, and it may need to be obtained from the diet.
Arginine supplementation seems to play a role in treating chronic inflammatory conditions. Arginine is necessary for the synthesis of polyamine and nucleic acid and can stimulate the secretion of the hormones prolactin, insulin, growth, and glucagon.
Some people promote arginine as a way to increase sperm count, muscle tone, physical stamina, and alertness. Children who are growing should avoid it because it might result in joint and bone deformities. Excessive doses of supplements may cause thickening of the skin.
Important functions and facts about arginine
- Accelerates wound healing
- Stimulates human growth hormone (HGH), which stimulates immune function
- Necessary for a normal sperm count
- Enhances fat metabolism
- Involved in insulin production
What is L-arginine?
L-arginine is one of the two forms of the amino acid arginine, the other being D-arginine. In the context of biological systems, L-arginine is the form that is naturally occurring and is biologically active.
L-Arginine, delivered via the gastrointestinal tract, is absorbed in the jejunum and ileum of the small intestine. A specific amino acid transport system facilitates the process and is also responsible for assisting with the transport of the other basic amino acids, L-lysine and L-histidine. The gastrointestinal enterocytes metabolize about 60% of the absorbed L-arginine, and only 40% makes it to the systemic circulation intact. Deficient intake of arginine produces symptoms of muscle weakness, similar to muscular dystrophy. Moreover, the high-energy compound NO-creatinine phosphate, essential for sustained skeletal muscle contraction, is also formed from L-arginine.
The proximal renal tubule accounts for much of the endogenous production of L-arginine from L-citrulline. In the tubule, arginine reacts via the Krebs cycle with the toxic ammonia formed from nitrogen metabolism, producing the nontoxic and readily excretable urea. Without this effective way to deal with metabolic waste and without getting enough L-arginine, ammonia would build up quickly, which is called hyperammonemia.
L-Arginine, its precursors, and its metabolites play a big role in how different metabolic pathways and interorgan signaling work together. The amino acid influences the internal environment in different ways: disposal of protein metabolic waste; muscle metabolism; vascular regulation; immune system function; healing and repair of tissue; formation of collagen; and building of new bone and tendons.
Benefits of L-arginine
A leading role for arginine has been shown in the endocrine system, vasculature, and immune response. It plays a crucial role in various physiological processes in the body. Here are some of the potential benefits associated with L-arginine:
1. Improved Blood Flow and Cardiovascular Health
- L-arginine is a precursor to nitric oxide (NO), a molecule that helps relax blood vessels, leading to improved blood flow.
- Some studies suggest that L-arginine may have positive effects on conditions such as high blood pressure and endothelial dysfunction.
- Enhanced blood flow may positively impact cardiovascular health and may be relevant for conditions such as erectile dysfunction (ED).
2. Exercise Performance and Muscle Growth
- L-arginine is involved in the synthesis of proteins, and it may contribute to muscle growth and repair.
- Some athletes and bodybuilders use L-arginine supplements with the belief that they can enhance exercise performance and recovery.
3. Wound Healing
- L-arginine plays a role in the synthesis of collagen, which is essential for wound healing and maintaining skin integrity.
- It may contribute to the healing process of injuries and surgical incisions. Following major surgery, it has been shown to reduce the patient's need to stay in the hospital.
4. Immune System Support
- L-arginine is involved in immune function, and its supplementation may support the normal functioning of the immune system. In fact, this amino acid is a component of most proteins and the substrate for several nonprotein, nitrogen-containing compounds acting as immune modulators. It could be an effective therapy for many pathophysiological conditions in humans, able to positively influence the immune response under some circumstances by restoring cytokine balance and reducing the incidence of infection.
5. Hormone Regulation
- L-Arginine functions as a secretagogue for a number of important hormones, which include pituitary, pancreatic, and adrenal hormones. It stimulates the release of growth hormones, prolactin, corticotrophin, and insulin in the body.
- Arginine is the most effective insulin secretagogue known, and it is used clinically to determine a patient's capacity to secrete insulin.
- Stimulates the release of prolactin
- Stimulates the release of ACTH
- Stimulates the release of growth hormone (GH), The GH-releasing activity of arginine is sex-but not age-dependent, being higher in females than in males but similar in children, youth, and elderly subjects.
6. Sperm Motility
- L-arginine is involved in the synthesis of sperm, and some studies have suggested that supplementation may improve sperm motility.
Arginine deficiency symptom
A deficiency of arginine impairs insulin secretion, glucose production, and liver lipid metabolism. Conditional deficiencies of arginine or ornithine are associated with the presence of excessive ammonia in the blood, excessive lysine, rapid growth, pregnancy, trauma, or protein deficiency, and malnutrition. Arginine deficiency is also associated with rash, hair loss and breakage, poor wound healing, constipation, a fatty liver, hepatic cirrhosis, and hepatic coma.
Toxicity symptoms of arginine
Depending on nutritional status and developmental stage, normal plasma arginine concentrations in humans and animals range from 95 to 250 mmol/L. Toxicity and symptoms of high intake are rare, but symptoms of massive dosages may include thickening and coarsening of the skin, muscle weakness, diarrhea, and nausea.
What arginine-rich foods should be avoided at the outbreak of a cold sore?
L-arginine is an amino acid that has been associated with the development and exacerbation of cold sores (oral herpes). While there's limited scientific evidence on the direct impact of arginine-rich foods on cold sores, some people believe that reducing arginine intake and increasing lysine intake may help manage outbreaks.
Lysine is another amino acid that is thought to counteract the effects of arginine and may help prevent or reduce the severity of cold sores. Therefore, during a cold sore outbreak, some individuals choose to avoid or limit arginine-rich foods and increase their intake of lysine-rich foods.
Food sources of L-arginine
Animal sources of L-arginine include chocolate, meat, dairy products, and eggs, and plant sources include seeds of all types, for example, grains, beans, and nuts. Here are some foods that are relatively high in l-arginine:
- Dairy products: cottage cheese, ricotta cheese, nonfat dry milk, skimmed yogurt.
- Seafood: halibut, lobster, salmon, shrimp, snails, and tuna.
- Beans: chickpeas and soybeans.
- Seeds: pumpkin, sesame, sunflower.
- Nuts: coconut, pecans, walnuts, almonds, hazel nuts, peanuts.
- Meat: beef (roasts, steaks), pork, poultry (chicken, turkey), wild game (pheasant, quail).
- Grains: wheat germ and flour, buckwheat, and oatmeal