Creatine (Cr) is the most popular nutritional supplement on the market, with yearly sales over $400 million¹. The reason for its popularity is simple: it works!  As you probably have read for the hundredth time...Cr is formed by combining the Amino Acids glycine, arginine, and methionine and is produced in physiologic amounts by the liver, kidneys, and pancreas². In addition to natural synthesis, Cr is also found in protein-rich sources such as meat and fish. The total daily requirement of Cr is 2 g/d, approximately half of which comes from in vivo production and the other half from dietary sources³.  The effects of oral Cr supplementation on contractile performance and metabolism of skeletal muscle recently have become an area of major interest in exercise physiology. Cr not only increases work performance but has recently been shown to increase muscle hypertrophy thru activation of satellite cell activity and increasing mRNA IGF-1 activity.  The evidence has accumulated over the last several years showing that Cr intake can elevate muscle Cr stores and improve one's capacity to perform maximal intermittent exercise such as resistance exercise ^{4, 5} but has no effect on endurance type of exercises⁷. 

Creatine Uptake...A Little Bit Goes a Long Way!

With Cr supplementation, a little bit goes a long way.  The research suggests that 3-5 grams is sufficient, some researchers suggest a even lower dosage depending on the amount of dietary Creatine consumed yet the exact dosage remains to be determined...anything more than that is not going to give additional gains.  In fact the bulk of Cr ingested at high dosage is excreted in the form of urinary Cr. Nobody likes pissing money down the drain..so low dose Cr is the way to go.  First, during dietary Cr supplementation, Cr accumulation is most pronounced in those individuals with the lowest initial Cr stores. When Cr was tested on vegetarian athletes, they made huge gains in strength because they consumed low endogenous dietary Cr.  Dietary sources include beef, tuna, cod, salmon, herring, and pork. The normal dietary intake of Creatine is 1-2 g/day, although vegetarians may consume less. Basically, individuals with the lowest starting intracellular Cr levels would be expected to have the highest initial Cr uptake rates. Consumption of Cr supplementation results in high intracellular rates that should rapidly expand the intracellular Cr pool. So what about bodybuilders whom consume large dietary sources of Cr that give an adult T-REX a run for his money? Individuals with initially high intracellular Creatine [Cr]i would not be expected to exhibit the marked increase in Cr uptake rate as for the individuals with low initial [Cr]i. In addition, the Cr uptake rate could be downregulated with a sustained extracellular Cr load when [Cr]i is normal or elevated, although this is reported only in the fast twitch muscle since fast twitch muscles contain the highest source of [Cr]i. 

When a bodybuilder first starts consuming Cr, accelerated uptake of Cr appears to occur initially, followed by a decline, possibly related to a decline in Cr transporter (CrT) number and the modulation of CrT activity associated with an increased [Cr]i⁸.  It's not necessary to take a lot as the Cr uptake capacity differs among skeletal muscle fiber types.  I would not worry about choosing a more expensive protein powder because it has Cr added to it, especially since after reading the article bodybuilders should be encouraged to be consuming low dosage Cr supplementation.  It's interesting that although type II b fibers explosive muscle fibers store more Cr than slow oxidative type I fibers, its interesting that one study reported that in rats whom were supplemented Cr for a few days the rates of Cr uptake were greatest in the slow-twitch muscle fibers and less in the fast-twitch type II fibers.  It is interesting the study that noted the Cr uptake rates were inversely related to the total resting Cr concentration within the fiber types. Regardless of the absolute value obtained under various experimental conditions, Cr uptake by the soleus muscle (a slow twitch fiber) was generally 45-70% greater than the uptake by the white gastrocnemius muscle (a fast twitch fiber). The greatest Cr uptake rate was observed in the fiber type with the smallest Cr content (soleus), whereas the opposite was true for the white gastrocnemius with the largest Cr content. Thus the fiber type with the highest Cr total content exhibits the lowest uptake rate.   Strikingly, the Cr content of the soleus is ~40% less than that of the white gastrocnemius muscle. Curiously, the increase in Cr uptake was observed in the high-oxidative fiber sections that possess relatively high mitochondrial contents and the cell fraction identified by Walzel and coworkers that contain the vast majority of the Cr transport proteins⁹. Based on the research low dose Cr supplementation is the way to go as fast twitch muscle fibers which contain the greatest potential for muscle hypertrophy can only store a limited amount, thereafter it's either excreted or shuttled into slow oxidative fibers.