What are the benefits of taking creatine (creatine monohydrate) for a healthy adult athlete with no pre-existing kidney or liver disease?

Benefits of Creatine Monohydrate Supplementation

For healthy adult athletes without kidney or liver disease, creatine monohydrate supplementation significantly improves high-intensity repeated sprint performance, increases muscle strength and power, enhances lean body mass by 1-2 kg, and may support cognitive function, with no negative health effects when following appropriate protocols. 1

Performance Enhancement Benefits

High-Intensity Exercise Performance

• Improves high-intensity repeated sprint performance by increasing muscle phosphocreatine stores by approximately 20%, which enhances rapid ATP resynthesis during explosive movements 1, 2
• Enhances performance in activities requiring repeated powerful contractions of short duration, such as sprinting, jumping, and resistance training 1
• Increases anaerobic work capacity, particularly beneficial for sports requiring multiple surges in intensity (cross-country skiing, mountain biking, cycling, triathlon) and end-spurts (rowing, kayaking, track cycling) 3

Strength and Muscle Adaptations

• Enhances training capacity and chronic training adaptations, including increased muscle strength, power, and lean body mass when combined with resistance training 1, 2
• Promotes faster muscle hypertrophy and accelerated recovery from atrophy compared to training alone 4
• Increases muscle protein synthesis following exercise, though this response is approximately 30% lower than traditional resistance exercise alone 2, 5

Metabolic and Recovery Benefits

• May promote muscle glycogen resynthesis in the first 24 hours post-exercise when taking 20g of creatine (5g doses on four occasions) beginning on the same day of fatiguing exercise 1
• Enhances glycogen accumulation and glucose transporter (GLUT4) expression when combined with training, potentially beneficial for daily glycogen depletion scenarios 4
• Lowers inflammation and oxidative stress, with potential to increase mitochondrial biogenesis 3

Cognitive Function Benefits

• May support brain function by increasing phosphocreatine stores in brain tissue, potentially improving cognitive processing 2, 5
• The mechanism parallels muscle benefits: enhanced ATP production in neural tissue supports cognitive demands 2

Recommended Supplementation Protocol

Loading and Maintenance Phases

• Loading phase: 20 g/day divided into four equal doses (5g each) for 5-7 days 1, 2, 5
• Maintenance phase: 3-5 g/day as a single dose for the duration of supplementation 1, 2, 5, 6
• Alternative low-dose approach: 2-5 g/day for 28 days avoids the body mass increase while remaining effective 1, 2, 5

Optimization Strategy

• Consume creatine with approximately 50g each of protein and carbohydrate to enhance muscle uptake via insulin stimulation 1, 2, 6
• After discontinuation, 4-6 weeks are required for muscle creatine levels to return to baseline 1, 2

Safety Profile and Expected Side Effects

Primary Side Effect

• The main side effect is a predictable 1-2 kg body mass increase, typically due to intracellular water retention or increased protein synthesis rather than pathological changes 1, 2, 5, 6
• This weight gain may offset benefits in weight-bearing endurance activities but is generally advantageous for strength and power sports 3

Established Safety Evidence

• No significant negative health effects have been reported when following appropriate supplementation protocols in healthy individuals 1, 2, 5, 6
• Short-term (5 days), medium-term (9 weeks), and long-term (up to 5 years at doses up to 30 g/day) supplementation is safe and well-tolerated 5, 7, 8

Critical Clinical Considerations

Kidney Function Monitoring

• Creatine may affect the evaluation of glomerular filtration rate (GFR) by altering exogenous creatinine generation, but does not affect actual kidney function itself 2, 5, 6
• If a patient develops evidence of renal dysfunction while taking creatine, discontinue the supplement 5
• Individuals with pre-existing kidney conditions should avoid creatine supplementation 5

Laboratory Interpretation

• When interpreting creatine phosphokinase (CPK) levels in athletes taking creatine, levels above 3000 U·L⁻¹ have been detected after maximal resistance exercise without pathological significance 5
• Consider creatine supplementation effects when evaluating serum creatinine levels for GFR assessment 5

Populations to Avoid

• Pregnant women should avoid creatine supplementation due to lack of safety evidence in this population 5
• Living kidney donors should be discouraged from creatine supplementation throughout the evaluation process 6

Mechanism of Action

• Creatine increases muscle creatine stores, enhancing the resynthesis of phosphocreatine, which serves as a rapid energy buffer for ATP regeneration during high-intensity exercise 1
• Functions by catalyzing the reversible reaction of phosphocreatine to rapidly re-phosphorylate ADP to ATP or store immediately available energy 2
• The elevated phosphocreatine content provides greater capacity to rapidly resynthesize ATP and buffer hydrogen ion accumulation during intense exercise 3