| Summary: | Abstract A novel creatine blend (creatine nitrate mixed with creatinine, CN‐CRN) has been anecdotally suggested to be superior to traditional creatine formulations for bioavailability and performance. However, does CN‐CRN supremely affects creatine levels in the blood and skeletal muscle of healthy humans remain currently unknown. This randomized, controlled, double‐blind, crossover trial evaluated the acute effects of single‐dose CN‐CRN on serum creatine levels, and 5‐days intervention with CN‐CRN on skeletal muscle creatine and safety biomarkers in healthy men. Ten healthy young men (23.6 ± 2.9 years) were allocated to receive either CN‐CRN (3 grams of creatine nitrate mixed with 3 grams of creatinine), pure creatine nitrate (3 grams, CN), or regular creatine monohydrate (3 grams, CRM) by oral administration. We found that CN‐CRN resulted in a more powerful rise in serum creatine levels comparing to either CN or CRM after a single‐dose intervention, as evaluated with the area under the concentration–time curve calculation (701.1 ± 62.1 (µmol/L) × min versus 622.7 ± 62.9 (µmol/L) × min versus 466.3 ± 47.9 (µmol/L) × min; p < .001). The peak serum creatine levels at 60‐min sampling interval were significantly higher in CN‐CRN group (183.7 ± 15.5 µmol/L), as compared to CN group (163.8 ± 12.9 µmol/L) and CRM group (118.6 ± 12.9 µmol/L) (p < .001). This was accompanied by a significantly superior increase in muscle creatine levels after CN‐CRN administration at 5‐days follow‐up, as compared to CN and CRM, respectively (9.6% versus 8.0% versus 2.1%; p = .01). While 2 out of 10 participants were found to be nonresponsive to CN intervention (20.0%) (e.g., no amplification in muscle creatine levels found at 5‐days follow‐up), and 3 participants out of 10 were nonresponsive in CRM trial (30%), no nonresponders were found after CN‐CRN administration, with individual upswing in total muscle creatine varied in this group from 2.0% (lowest increment) to 16.8% (highest increment). Supplemental CN‐CRN significantly decreased estimated glomerular filtration rate (eGFR) at 5‐days follow‐up, as compared to other interventions (p = .004), with the average reduction was 14.8 ± 7.7% (95% confidence interval; from 9.3 to 20.3). Nevertheless, no single participant experienced a clinically relevant reduction in eGFR (< 60 ml/min/1.73 m2) throughout the course of the trial. Liver enzymes remained in reference ranges throughout the study, with no participant experienced high liver blood tests (e.g., AST > 40 units per L or ALT >56 units per L). Besides, no participant reported any major side effects during the trial, while the odors of CN‐CRN and CN formulations were considered somewhat unpleasant in 8 out of 10 participants (80.0%). Our results suggest that CN‐CRN is a preferred and relatively safe alternative to traditional creatine formulations for improved creatine bioavailability in the blood and skeletal muscle after single‐dose and 5‐days interventions.
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