Creatine: Complete Overview

1. Biochemistry & Synthesis

• Arginine + Glycine → (via amidinotransferase, in kidneys) → Guanidinoacetate
• Guanidinoacetate → (via methyltransferase + S-adenosylmethionine, in liver) → Creatine

2. How It Works - The Phosphocreatine System

• Lippincott's Illustrated Reviews: Biochemistry, 8th ed., p. 812-813
• Harper's Illustrated Biochemistry, 32nd ed., p. 323

3. Creatinine - The Degradation Product

• Urinary creatinine output (~1-2 g/day in adult males) is proportional to total muscle mass - used to verify complete 24-hour urine collection
• A rise in serum creatinine signals impaired renal clearance (kidney malfunction), since it is normally cleared rapidly
• Loss of muscle mass (paralysis, muscular dystrophy) → reduced urinary creatinine

4. Supplementation

Forms

Dosing Protocols

Performance Benefits (Evidence-Based)

• Strength and power: Increases maximal strength, peak power, and sprint performance, particularly in repeated high-intensity bouts (<30 seconds)
• Muscle hypertrophy: Augments lean mass gains when combined with resistance training - partly via increased training volume, partly via cellular hydration
• Recovery: May reduce muscle damage markers and assist post-exercise glycogen resynthesis
• Cognitive function: Emerging evidence for benefits in sleep-deprived individuals and older adults (creatine is found in brain tissue, not just muscle)

5. Safety

6. Clinical Notes

• Creatine kinase (CK) isoforms have diagnostic value: the MB isoform elevated in serum indicates myocardial damage (MI marker)
• Creatine deficiency syndromes (rare inborn errors of creatine synthesis or transport) present in children as intellectual disability, seizures, and speech delay
• Serum creatinine is a standard kidney function marker - but note that creatine supplementation can modestly raise serum creatinine (not reflecting actual kidney damage), which can confuse interpretation

Creatine for the Gym

How It Works (Simple Version)

Phosphocreatine + ADP  →  Creatine + ATP  (instant energy)

• You can push one or two more reps on a heavy set
• You recover faster between sets
• Over weeks, those extra reps add up to more muscle and strength

What It Actually Does For You in the Gym

Should You Take It?

• Do resistance training (weights, CrossFit, powerlifting)
• Do any explosive sport (sprinting, martial arts, football)
• Are vegetarian or vegan (you get very little dietary creatine - animal products are the main food source, so you benefit most from supplementing)
• Are over 50 (helps preserve muscle mass and emerging evidence supports cognitive benefits too)

• Only do steady-state cardio (jogging, cycling at moderate pace) - creatine helps short, explosive efforts, not endurance
• Already eat a lot of red meat and fish (your levels may already be fairly saturated)

How to Take It

• Simple approach: 3-5 g every single day. That's it. Mix in water, a shake, juice - doesn't matter.
• Loading (optional): 20 g/day (split into 4 doses) for 5-7 days, then 3-5 g/day. Saturates your muscles faster but you end up in the same place after ~4 weeks either way.

Side Effects / Safety

• Very safe for healthy people. Side effect rates in clinical trials are the same as placebo (about 13-14% each), meaning creatine is not actually causing them.
• Water weight: You'll gain 1-2 kg in the first week - this is water being pulled into muscle cells (intracellular hydration), not fat. It's actually a good sign.
• GI discomfort: Rare, usually from taking too much at once (common during loading). Split the dose if this happens.
• Kidney concerns: No evidence of harm in healthy people. If you have pre-existing kidney disease, check with your doctor first.

The Practical Bottom Line

Buy plain creatine monohydrate powder. Take 3-5 g daily, mixed into anything. Don't overthink timing or loading. Train hard. That's the whole protocol - backed by 30+ years of research.