Creatine.
The body's energy buffer — and the most-studied supplement on earth?
Creatine is a molecule your body already makes (in the liver and kidneys from three amino acids) and already stores (in muscle, at ~95% of the body's pool) — a compound whose job is singular and fundamental: to buffer ATP, the cellular energy currency, millisecond to millisecond. When a muscle fires or a neuron spikes, the initial energy does not come from oxygen or food — it comes from phosphocreatine, the instantly-tapped reserve that regenerates ATP in the split second before metabolism catches up. Supplementation raises this buffer ~20–40% — and the result is the best-replicated performance finding in sports nutrition: more high-intensity work capacity, better training quality, and (over weeks of accumulated training) more strength and muscle. And the brain — the body's other insatiable ATP consumer — carries the same system, which is why creatine is quietly becoming the most evidence-backed nootropic on the shelf (our brain page's framing).
Creatine (methylguanidinoacetic acid)
A nitrogenous organic acid synthesized from glycine, arginine, and methionine — made in the liver and kidneys, stored primarily in skeletal muscle (~120 g in a 70 kg adult), and consumed through diet (meat and fish carry ~1–2 g per serving). The body's total pool (~120–140 g) is the phosphocreatine energy system: the reserve that regenerates ATP faster than any metabolic pathway can. Vegetarians carry measurably lower baseline stores — the group with the most to gain.
The headline mechanism: phosphocreatine donates a phosphate to ADP, regenerating ATP in milliseconds — faster than glycolysis, faster than oxidative metabolism. The buffer for every burst of high-intensity effort.
More reps per set, more sprints per session, more quality work — the best-replicated performance finding in sports nutrition. The mechanism: a bigger buffer delays fatigue in the 10–30 second energy window.
The accumulated-training effect: more work per session compounds into more strength and more muscle over weeks and months — the training-multiplier framing our muscle-strength page teaches.
The brain runs on the same buffer — and supplementation trials show cognitive benefits under sleep deprivation, stress, and aging, with vegetarians (whose diets carry no creatine) showing the largest effects. Our brain page's nootropic story.
Creatine draws water into muscle cells — the cell-swelling effect that is anabolic signaling in its own right (and the source of the 1–2 kg early water weight).
The sarcopenia evidence: creatine plus resistance training outperforms training alone in older adults — the preservation angle our sarcopenia pages carry as Tier 1 adjunct evidence.
The phosphocreatine system is the body's instant-energy circuit: at the sites of highest ATP demand (contracting muscle, firing neurons), the enzyme creatine kinase catalyzes the transfer of a phosphate from PCr to ADP — regenerating ATP ~10 times faster than oxidative metabolism can. The system is a shuttle, not a fuel: PCr is regenerated during rest from mitochondria's output, positioned at the sites of use, and drawn down during each burst. Supplementation expands the shuttle's capacity ~20–40% — more stored PCr means more high-intensity work before the buffer drains, and a faster resynthesis between efforts. The mechanism is identical in the brain, where neurons' fluctuating energy demands meet the same buffer — the neurology of the nootropic story.
Monohydrate Powder
The trial standard, 5 g daily
Micronized Powder
Mixability refinement
HCl Capsules
Solubility premium, thinner evidence
'Buffered' & Liquid Forms
The degradation traps
Creatine Monohydrate ✅
Nearly 100% bioavailable, the form in essentially every trial ever conducted — the performance evidence, the safety record, the cognitive studies, the aging-muscle trials. A commodity chemical: Creapure and reputable generics are the same molecule. Micronization improves mixing, not chemistry. The default, always.
HCl, and the Premium Forms
Creatine HCl dissolves ~40× better — a real solubility advantage that permits smaller doses and claims of less bloating. But the OUTCOME evidence is monohydrate evidence; the premium buys comfort, not proven superiority. 'Buffered' creatine (Kre-Alkalyn) failed its head-to-head with monohydrate outright.
The 1992 Barcelona Games — The Debut
Creatine's public history begins on a podium. At the 1992 Barcelona Olympics, the British sprinter Linford Christie won 100m gold and Sally Gunnell took 400m hurdles gold — and both were reported to be using creatine, then nearly unknown outside exercise physiology. The Times of London ran the story; the supplement industry was born overnight, and the research race followed.
The science rose to the attention: since Barcelona, creatine has become the most-studied supplement in human history — by the mid-2000s, over 500 peer-reviewed trials; by the 2020s, well over 1,000, spanning performance, muscle disease, cognition, aging, and safety. The International Society of Sports Nutrition's position stand (updated repeatedly) concludes with the field's most confident sentence: creatine is the most effective legal nutritional supplement for increasing high-intensity exercise capacity and lean mass. The molecule from Barcelona became the benchmark every other sports supplement is measured against.
The arc from Olympic gold to geriatric-medicine adjunct is the full story: the same buffer that adds a rep to a sprinter's set adds a functioning year to an older adult's muscle — the performance science and the aging science converging on one molecule. Our muscle pages carry the training story; our brain page carries the nootropic story; this page carries the molecule.
- Body pool: ~120–140 g in a typical adult, ~95% in skeletal muscle — the storage target that supplementation expands.
- Daily turnover: ~2 g per day, replaced by synthesis (~1 g) and diet (~1 g from meat and fish) — the balance supplementation increases.
- The vegetarian baseline: plant-based diets carry zero creatine — vegetarians' muscle stores run lower, and supplementation produces their largest observed effects (muscle AND cognitive).
- The performance window: effects concentrate in the 10–30 second high-intensity zone (sprints, reps, bursts) — the phosphocreatine system's domain.
- Timing is minor; consistency is everything: daily, any time, no cycling — the habit is the protocol.
What It Does NOT Do
The honest negative space — the category's persistent inflations:
- It is not an anabolic steroid. Creatine is a food-derived compound the body already makes — the mechanism is energy buffering, not hormone signaling. The muscle gains come from accumulated better training, not from the molecule directly building tissue.
- It does not damage healthy kidneys. The most-tested safety question in supplement history: decades of trials, including multi-year studies in healthy adults at 5–10 g daily, show no kidney harm. The creatinine confusion (Chapter 3) — creatine's breakdown product is the kidney-test marker — caused the myth and sustains it.
- It does not require loading or cycling. The loading phase is a speed option, not a requirement; the cycling theory (stores 'downregulate') is folklore contradicted by the continuous-use data. Daily 3–5 g, forever if desired.
- It does not help every exercise equally. The effects concentrate in high-intensity, repeated-effort activity (sprints, resistance training). Endurance performance at steady state — the oxidative domain — shows little to no benefit.
- It does not work without training. The performance gains are training gains — more quality work per session, compounding. Without resistance training, the muscle story largely doesn't happen (the brain story is separate and does not require training).