Two independent analyses using different NHANES cycles found a consistent direction: more dietary creatine, less reported cancer. Both survived adjustment for age, sex, race, BMI, smoking, alcohol, and physical activity. The association is reproducible across datasets.

The effect sizes are tiny. Ostojic found a 1.1 mg/kg/day difference in creatine intake between cancer-free and cancer groups. That is roughly the creatine in one additional ounce of chicken. The Jiang study's OR of 0.95 per standard deviation is barely distinguishable from null. These are small numbers made statistically significant by large sample sizes.

NHANES is the gold standard for population-level nutritional surveillance in the U.S. Both studies used appropriate complex survey design weighting. Jiang's 25,879 participants across six cycles provide broad coverage. Multiple covariate adjustments were reasonable and standard.

Both studies measured cancer as "Have you ever been told by a doctor that you had cancer?" This captures prevalent cancer (including survivors diagnosed years or decades ago), not incident cancer. People who have been diagnosed with cancer frequently change their diet. They eat less red meat. They lose appetite. They develop cachexia. So the association may simply be: cancer → less meat → less creatine. Not: less creatine → cancer.

Ostojic acknowledges this. Jiang acknowledges this. Neither can fix it, because a cross-sectional design cannot establish which came first. A longitudinal cohort study measuring creatine intake in healthy people and following them for incident cancer would be the minimum design needed to take this hypothesis further. Neither study is that.

Both studies estimated dietary creatine from food codes (meat, fish, poultry) using a conversion factor of roughly 0.11 g per ounce. This ignores several realities. Cooking method matters (creatine degrades with heat). Endogenous creatine synthesis (the body makes about 1 g/day in the liver and kidneys) was not accounted for. Creatine supplements, used by roughly 30% of gym-going adults, were entirely excluded. Two days of 24-hour dietary recall is a narrow window to represent a person's habitual diet.

As a nephrologist would note: serum creatinine (a creatine metabolite) is influenced by kidney function, muscle mass, and hydration status. None of this was factored in. People with reduced kidney function have altered creatine metabolism that these food-code estimates cannot capture.

People who consume more creatine eat more protein, which correlates with higher income, better access to healthcare, more physical activity, and generally healthier lifestyles. Despite statistical adjustment, the covariates controlled for (BMI, smoking, activity) cannot fully capture the "healthy user" effect. Notably, fish and seafood, which contribute to creatine estimates, also deliver omega-3 fatty acids, vitamin D, and selenium, all of which have their own proposed anticancer properties. The studies did not disentangle creatine from these co-travelers.

Ostojic himself notes: "we failed to analyze the possible role of other nutrients in creatine-containing foods." That is a significant concession.

Lead author Sergej M. Ostojic serves on the Scientific Advisory Board on Creatine in Health and Medicine (AlzChem LLC, a creatine manufacturer). He co-owns a European patent on liquid creatine supplements. He has received research funding from AlzChem GmbH, ThermoLife International, and Hueston Hennigan LLP (a law firm that has represented supplement companies). To his credit, these are fully disclosed in the paper. But a study finding that creatine is associated with less cancer, led by an author with financial ties to the creatine industry, warrants an extra layer of skepticism. The Jiang study has no declared conflicts.