Writing in Nutrition Reviews, leading creatine researcher Sergej Ostojic, MD, PhD, integrates physiological turnover data, endogenous synthesis estimates and population‑level dietary exposure to calculate adequate intake (AI) values for adults between the ages of 19 and 65 years old and to address what he identified as a major gap in nutrition science.
“Despite decades of research on creatine metabolism and supplementation, there are still no formal dietary reference values for creatine in adults,” he said. “As a result, creatine is largely absent from nutrient databases and dietary guidelines, which limits our ability to assess intake or consider its role in public health nutrition.”
The paper also highlights significant gaps in food‑composition data, noting that creatine is currently absent from major nutrient databases such as USDA FoodData Central, complicating dietary assessment and public‑health monitoring.
Why adults need dietary creatine
Creatine plays a critical role in energy buffering, particularly in tissues with high and fluctuating energy demands such as skeletal muscle—which accounts for 95% of the body’s creatine pool and is used to support muscle contraction and recovery. The remaining creatine and phosphocreatine are distributed among other metabolically active tissues, including the brain, heart, retina, testes and blood.
Although humans can synthesize creatine from amino acids, Dr. Ostojic notes that this endogenous production does not fully offset daily losses caused by its irreversible conversion to creatinine and subsequent urinary excretion.
“In adults, creatine is continuously converted to creatinine and excreted, with average losses estimated at about 20 mg/kg/day in men and 15 mg/kg/day in women,” he said. “Evidence suggests that roughly three-quarters of these losses are replenished through internal synthesis, while the remaining portion must come from the diet.”
Based on this balance, the proposed adequate intakes are 5.4 mg/kg/day for men (around 400 mg/day) and 4.1 mg/kg/day for women (around 240 mg/day).
“Emerging population-level evidence suggests that insufficient dietary creatine intake may be associated with adverse health outcomes across several domains, including mental health, cognition, liver health, reproductive function, cancer and gastrointestinal physiology.” Dr. Ostojic noted.
Though evidence is still emerging and methodologically diverse, the proposal to classify creatine as a conditionally essential nutrient reflects the idea that the body’s own production may not always be sufficient to maintain optimal tissue levels.
Who may fall short on creatine
While most adults are likely to meet these intake levels through a typical diet that contains meat, fish or dairy products, population data showing that a meaningful minority (3% to 10%) report no measurable dietary creatine intake. Studies consistently report lower circulating and intramuscular creatine concentrations in vegetarian populations compared with omnivores.
“Although these associations remain preliminary and derive from heterogeneous study designs, they collectively indicate that creatine requirements may not be fully met in certain subgroups, such as older adults, individuals with low meat intake, and those with increased metabolic demands, under specific physiological or dietary conditions,” Dr. Ostojic noted.
He added that the proposed adequate creatine values for offsetting daily losses may need to be adjusted for people trying to build or preserve muscle and that the additional creatine required to enhance performance or promote muscle growth is modest relative to baseline maintenance needs.
“Importantly, while creatine is a critical component for skeletal muscle energetics and growth, muscle hypertrophy depends on multiple factors beyond creatine availability,” he wrote, adding that synergistic effects require input from different macronutrients, micronutrients and exercise stimulus. “The effectiveness and safety of supplemental creatine in health and disease, however, fall outside the scope of this review and are covered extensively elsewhere.”
As part of a wider project to determine creatine requirements across life stages and physiological conditions—which includes a previously published paper on establishing creatine reference intakes in children, Dr. Ostojic calls for improved food databases, better biomarkers of creatine status and targeted research in vulnerable populations to refine future recommendations.
“Priority populations include older adults, pregnant and lactating women, children older than one year, and adolescents,” he said. “Future studies will also aim to refine measurements of endogenous synthesis, non-renal creatine losses and functional outcomes associated with creatine status.”
Ultimately, the goal is to build a stronger evidence base that could support formal evaluation by organizations responsible for establishing DRIs, such as the National Academies of Sciences, Engineering, and Medicine (NASEM).
Source: Nutrition Reviews. doi: 10.1093/nutrit/nuag009. “Establishing Dietary Reference Intakes for Creatine in Adults”. Author: Sergej Ostojic.
