How bioavailable is creatine?
The total bioavailability of creatine is unknown. Some creatine is degraded to creatinine in the GI tract, but the amount is probably low (one study estimated about 2%). It is believed that it is actively transported in the intestine by a saturable transporter. As the dosage of creatine increases, the time to maximal concentration and half-life increase. High doses, such as 20 g, cause an increase followed by a plateau in blood creatine levels lasting about six hours before dropping. transporter. This transporter is highly selective for The main limiting factor for muscle creatine uptake is the creatinecreatine. Another naturally occuring compound, beta-guanidinopropionic acid, also competes for the creatine transporter. As levels of creatine in muscle tissue increase, the creatine transporter downregulates. This makes it so muscle tissue can only store a certain limited amount of creatine. Although this amount is not maximized in most individuals not supplementing with creatine, the l
