People who don't eat meat get almost no creatine from food, so their bodies make more of it themselves — and that's enough to keep their brain and muscles working just as well as meat-eaters.

Taking creatine supplements at 10–20 grams per day for six weeks does not lead to measurable changes in body fat, muscle mass, how much people move, or how many calories they consume.

Taking creatine supplements can slightly boost the amount of creatine in your brain—by about 3 to 10%—but not as much as it boosts your muscles, probably because your brain is harder to reach with supplements and makes some creatine on its own.

Taking creatine supplements at 10 or 20 grams per day for six weeks does not improve how quickly healthy young adults process information, remember events, or make decisions.

Creatine supplements may not improve brain function in healthy young adults because the dose, length of use, or starting levels of creatine in the body might be too low or too variable, and the study did not directly measure brain creatine levels.

Taking creatine for 5 days doesn’t boost muscle fuel stores in healthy young guys who aren’t working out or eating extra carbs — it needs more than just the supplement to make a difference.