The literature on creatine biomarkers in various bodily fluids remains limited. The purpose of this review is to explore the available data regarding the presence of molecules considered biomarkers of creatine metabolism—namely creatine, guanidinoacetate, and creatinine—across different bodily fluids and matrices. In addition to providing reference values for each biofluid, the paper reports concentrations of these biomarkers in different pathologies. The impairment of creatine metabolism is most extensively studied in creatine deficiency syndromes, which are characterized by genetic deficiencies in either the enzymes involved in creatine biosynthesis or creatine transport. However, other conditions may also influence creatine metabolism to some extent. Our paper also focuses on the transport pathways of these metabolites from their originating tissues to various bodily fluids, typically mediated by the creatine transporter (SLC6A8), with evidence suggesting the involvement of other transporters as well. Gas and liquid chromatography have replaced traditional methods for the analytical detection of biomarkers of creatine metabolism and are now commonly used for this purpose. The paper also discusses the differences and variations between these analytical methods.

Background and Objectives: Preliminary studies indicate that dihydrogen (H₂) may affect molecular pathways involved in appetite regulation; however, its role in influencing patient-reported appetite outcomes in individuals with obesity remains uncertain. This randomized, placebo-controlled, double-blind trial aimed to evaluate the effects of H₂ supplementation on appetite, body composition, sleep quality, obesity-specific quality of life, and related biomarkers in obese men and women. Materials and Methods: The study included 36 participants (24 females; age 42.1 ± 13.2 years; BMI 30.8 ± 4.2 kg/m²) randomized to receive either 1.0 L of hydrogen-rich water (15 mg of H₂) or 1.0 L of control water (0 mg of H₂) daily for eight weeks. Results: The results demonstrated that hydrogen-rich water significantly mitigated cravings (p = 0.05), improved subjective sleep quality (p = 0.05), reduced total cholesterol (p = 0.02) and LDL cholesterol (p = 0.04), and increased plasma glucagon-like peptide-1 levels (p = 0.05) compared to the control. No severe adverse effects were reported throughout the trial. Conclusions: These findings suggest that hydrogen-rich water may serve as a safe and effective dietary strategy to address appetite regulation and related metabolic indices in individuals with obesity. The study is registered at ClinicalTrials.gov (NCT06722326).

Background and Aims: Preliminary studies indicate that dihydrogen (H₂) may affect molecular pathways involved in appetite regulation; however, its role in influencing patient-reported appetite outcomes in individuals with obesity remains uncertain. This randomized, placebo-controlled, double-blind trial aimed to evaluate the effects of H₂ supplementation on appetite, body composition, sleep quality, obesity-specific quality of life, and related biomarkers in obese men and women. Methods and Results: The study included 36 participants (24 females; age 42.1 ± 13.2 years, BMI 30.8 ± 4.2 kg/m²) randomized to receive either 1.0 L of hydrogen-rich water (15 mg of H₂) or 1.0 L of control water (0 mg of H₂) daily for eight weeks. Results demonstrated that hydrogen-rich water significantly mitigated cravings (P = 0.05), improved subjective sleep quality (P = 0.05), reduced total cholesterol (P = 0.02) and LDL cholesterol (P = 0.04), and increased plasma glucagon-like peptide-1 levels (P = 0.05) compared to the control. No severe adverse effects were reported throughout the trial. Conclusions: These findings suggest that hydrogen-rich water may serve as a safe and effective dietary strategy to address appetite regulation and related metabolic indices in individuals with obesity. The study is registered at ClinicalTrials.gov (NCT06722326).

Background: Hydrogen-infused water (HIW) has attracted considerable interest over the past two decades due to its potential health benefits. However, its effects on exercise performance and hydration biomarkers remain inadequately explored, particularly in physically active populations such as collegiate athletes. This study aimed to investigate the impact of medium-term HIW supplementation on running performance, hydration biomarkers, and health-related quality of life in collegiate athletes. Methods: A randomized, double-blind, placebo-controlled, crossover trial was conducted with twelve collegiate athletes (age: 25.1 ± 3.5 years, six female). Participants consumed 660 mL daily of either HIW (300 µmol/L dihydrogen) or control water (0 µmol/L dihydrogen) for four weeks, with a two-week washout period between interventions. Exercise performance was assessed using an incremental running-to-exhaustion test with a breath-by-breath metabolic system. Hydration biomarkers were measured using multi-frequency bioelectrical impedance analysis, and health-related quality of life was evaluated using the SF-36 survey. The trial was registered with ClinicalTrials.gov (NCT06788015). Results: HIW supplementation significantly increased maximum running velocity and velocity at the anaerobic threshold compared to control water (P < 0.05). Mental and general health scores on the SF-36 survey were significantly higher after HIW supplementation (P = 0.05 and P = 0.03, respectively). A trend toward increased intracellular water and body minerals was observed following HIW consumption (P < 0.20). No adverse effects were reported throughout the study. Conclusion: Our findings indicate that HIW is a safe and potentially effective intervention for enhancing both physical performance and overall well-being in active individuals. Larger studies are needed to confirm these findings and elucidate the underlying mechanisms.