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Creatine — Grokipedia Fact-checked by Grok 11 days ago Creatine Ara Eve Leo Sal 1x <!--Infobox Start [Chemical Compounds]--> | name = Creatine | iupac_name = N-(aminoiminomethyl)-N-methylglycine | other_names = N-Carbamimidoyl-N-methylglycine | Methylguanidoacetic acid | N-Amidinosarcosine | 2-[Carbamimidoyl(methyl)amino]acetic acid | chemical_formula = C₄H₉N₃O₂ | molar_mass = 131.13 g/mol | appearance = white, odorless crystals | density = 1.33 g/cm³ | melting_point = Decomposes ~300 °C | solubility_in_water = 13 g/L (20 °C) | pka = 3.429 | log_p = -1.258 | cas_number = 57-00-1 | pubchem_cid = 586 | chemspider_id = 566 | unii = MU72812GK0 | smiles = CN(CC(=O)O)C(=N)N | inchi = InChI=1S/C4H9N3O2/c1-7(4(5)6)2-3(8)9/h2H2,1H3,(H3,5,6)(H,8,9) Key: CVSVTCORWBXHQV-UHFFFAOYSA-N | zwitterionic_form = Predominantly zwitterionic at physiological pH (COO⁻ and protonated guanidino group) | physiological_role = Facilitates rapid ATP regeneration via phosphocreatine system in muscle and brain tissues | phosphorylated_form = phosphocreatine | biosynthesis_precursors = arginine | glycine | methionine | dietary_sources = red meat | fish | common_supplement_form = creatine monohydrate | typical_supplement_dosage = 3–5 g/day | discovered = 1832 | discoverer = Michel Eugène Chevreul <!--Infobox End--> Creatine (also spelled creatin) is a naturally occurring organic compound with the chemical formula C₄H₉N₃O₂ , classified as a non-protein amino acid derived from glycine , and it plays a crucial role in energy metabolism by facilitating the rapid regeneration of adenosine triphosphate (ATP) through the phosphocreatine system in muscle and brain tissues. [1] [2] [3] Endogenously synthesized primarily in the liver, kidneys, and pancreas from the amino acids arginine , glycine , and methionine , creatine is stored as phosphocreatine in vertebrate tissues, where it supports high-intensity, short-duration activities such as sprinting or weightlifting by donating phosphate groups to ADP for ATP replenishment. [2] [4] [5] It is also obtained through dietary sources like red meat and fish , though daily endogenous production accounts for about 1 gram in adults, with the remainder derived from food or supplements. [6] As a popular dietary supplement , particularly in the form of creatine monohydrate, it is widely used to enhance athletic performance, increase muscle mass, and improve recovery. According to the International Society of Sports Nutrition (ISSN) 2025 position stand, the most effective strategy for rapidly saturating muscle creatine stores is a loading phase of 0.3 g/kg/day (typically 20-25 g/day, divided into doses) for 5-7 days, followed by a maintenance dose of 0.05-0.15 g/kg/day (commonly 3-5 g/day). Loading is not mandatory; consistent lower doses (e.g., 3 g/day for approximately 28 days) can achieve full saturation over time without a loading phase. A general intake of 2-3 g/day is suggested for health benefits in all individuals. Extensive research, including recent studies from 2024-2025, confirms the safety and efficacy of these protocols in healthy individuals. [7] [8] [5] [2] Creatine supplementation is generally not recommended for patients with CKD stage 3 or eGFR below 60 mL/min/1.73m² due to insufficient evidence of safety, potential to elevate serum creatinine (falsely suggesting worsening kidney function), and possible risks in those with preexisting kidney problems. Authoritative sources like Mayo Clinic state it might be unsafe for people with kidney issues, and further research is needed. [9] [10] Individuals with preexisting kidney conditions should consult a physician before supplementation, as it may elevate serum creatinine levels independently of actual kidney damage, potentially complicating diagnostic assessments. [11] [12] Beyond exercise, creatine exhibits neuroprotective properties and has shown potential benefits in brain function, including alleviating symptoms in certain psychiatric and neurological disorders, particularly major depressive disorder as an adjunct to antidepressant pharmacotherapy (such as SSRIs) or psychotherapy. Some evidence suggests faster onset of antidepressant effects in women and potential mechanisms via improved brain energy metabolism. However, a 2025 systematic review and meta-analysis reported a small effect size (SMD -0.34, 95% CI -0.68 to -0.00) on depressive symptoms, equivalent to a 2.2-point reduction on the 17-item Hamilton Depression Rating Scale (below the minimal important difference of 3.0 points), with very low certainty of evidence and substantial heterogeneity, concluding that benefits may be limited and more rigorous trials are required. [13] [14] Emerging evidence from recent meta-analyses and studies also suggests potential cognitive benefits in healthy individuals, such as improved memory, attention, processing speed, and reduced mental fatigue during sustained or demanding cognitive tasks, particularly under conditions of stress or sleep deprivation. [1] [15] [16] [17] [18] These cognitive and mood benefits appear more pronounced in women, who tend to have lower baseline brain creatine levels—particularly in the frontal lobe—compared to men, potentially leading to greater responsiveness to supplementation. [19] Creatine supplementation provides some benefits for women without concurrent exercise, primarily in cognitive function (improved memory, attention, and processing speed) and mood enhancement (especially as an adjunct for depression), with potential minor improvements in bone health markers and functional performance in postmenopausal women. The evidence is stronger for these cognitive and mood benefits than for muscle or strength gains without exercise. [19] [20] It is ultimately metabolized and excreted as creatinine via the kidneys, with non-enzymatic degradation occurring at a rate of about 1.7% per day. [1] [10] Creatine supplementation can further increase serum creatinine concentrations, which does not necessarily indicate renal impairment but may require alternative markers for accurate kidney function evaluation. [12] [11] Chemical Properties and Biosynthesis Molecular Structure Creatine is an organic compound with the molecular formula C₄H₉N₃O₂ and a molecular weight of 131.13 g/mol. [1] It functions as a guanidino compound, specifically N-(aminoiminomethyl)-N-methyl glycine , derived from the amino acids glycine , arginine , and methionine . [1] The molecular structure features a central carbon chain with a carboxylic acid group, an N-methyl group, and a guanidino moiety, which contributes to its role in energy metabolism . [1] At physiological pH , creatine predominantly exists in its zwitterionic form, where the carboxylic acid group is deprotonated (COO⁻) and the guanidino group is protonated, resulting in a net neutral charge. [21] This form enhances its solubility in water , reported at approximately 13 g/L at 20°C. [1] Creatine appears as white, odorless crystals with a density of 1.33 g/cm³ and is stable in solid form, but it decomposes at around 300°C without melting. [1] In aqueous solutions, however, it exhibits limited stability due to spontaneous, non-enzymatic cyclization to creatinine via dehydration. [22] Creatine can be reversibly phosphorylated to form phosphocreatine , a key energy storage molecule, through the reaction catalyzed by the enzyme creatine kinase : creatine + ATP ⇌ phosphocreatine + ADP \text{creatine} + \text{ATP} \rightleftharpoons \text{phosphocreatine} + \text{ADP} creatine + ATP ⇌ phosphocreatine + ADP This equilibrium facilitates rapid phosphate transfer in cells. [23] The process underscores creatine's biochemical versatility without altering its core molecular integrity under physiological conditions. [24] Biosynthetic Pathways Creatine is endogenously synthesized in humans through a two-step enzymatic pathway that utilizes the amino acids arginine , glycine , and methionine as precursors. The initial step occurs predominantly in the kidneys, where the mitochondrial enzyme L-arginine: glycine amidinotransferase (AGAT; EC 2.1.4.1) catalyzes the transfer of an amidino group from L- arginine to glycine , yielding guanidinoacetate (GAA) and L-ornithine. This reaction is the rate-limiting step in creatine production. The GAA is subsequently transported via the bloodstream to the liver, where the cytosolic enzyme guanidinoacetate N-methyltransferase (GAMT; EC 2.1.1.2) transfers a methyl group from S-adenosyl methionine (derived from methionine ) to GAA, forming creatine and S-adenosylhomocysteine. [25] [26] In adults, endogenous creatine synthesis produces approximately 1-2 g per day, accounting for roughly half of the total creatine turnover, with the remainder supplied by dietary sources to maintain the body's estimated 120 g creatine pool (primarily in skeletal muscle ). This production rate corresponds to the daily loss of creatine as creatinine via urine , ensuring steady-state levels under normal conditions. Minor contributions to synthesis occur in the pancreas and other tissues, but the kidney-liver axis dominates the process. [27] [25] Following synthesis, creatine is released into the circulation and actively transported into target tissues, including skeletal muscle , cardiac muscle , and brain , by the creatine transporter 1 (CRT1), a plasma membrane protein encoded by the SLC6A8 gene on the X chromosome . This sodium- and chloride-dependent transporter facilitates creatine uptake against concentration gradients, enabling accumulation in cells where it supports energy homeostasis . Defects in SLC6A8 impair this transport, highlighting its essential role. [28] [29] The biosynthetic pathway is tightly regulated to match physiological demands, primarily through feedback inhibition at the AGAT step: elevated creatine or cyclocreatine levels suppress AGAT transcription and activity, reducing GAA formation. Hormonal influences also modulate expression; for instance, growth hormone upregulates AGA