Originally Posted by TennisCoachFLA
Protein supplements and multivitamins are simply excreted by the body. A balanced and healthy diet is all that is needed. If your doctor runs a lab panel that shows a deficiency, then you would need supplementation. But the vast majority of us are just fine without any of that stuff.
Creatine is also a myth and in your head. It simply causes you to retain water. The body can not process the massive amounts of creatine in a supplement.
In a double blind study, creatine had no more effect than a placebo in regards to improving endurance. Studies also found that combining with caffeine, common in supplements, completely obliterates all effects of creatine.
I don't agree with your initial assertion, however I do agree with the majority of your first paragraph. Your premise is incorrect, however the remainder of it has seemed to be by and large true.
Creatine is absorbed and converted to phosphocreatine (PCr) - basic biochemistry. PCr is later available as a phosphate donor for the ADP->ATP conversion, again basic biochemistry. That's all creatine does. It is phosphorylated for later use, and readily gives up phosphate ions when necessary. It's pretty easy to see here why putting someone on a treadmill until exhaustion won't show much difference - a typical method for test of endurance. Using a flawed test is, in the words of Scott Adams, like trying to find unicorns in your sock drawer - a flawed test proves little. Bloating/water retention is a normal side effect - however for some reason we always associate that negatively.
That said, the mentality of 'creatine makes me stronger' is completely erroneous. It is readily available from the above that this is simply not the case. The abundance of phosphate for the Krebs cycle does not cause this effect. The feeling of being 'larger' is typically due to the aforementioned bloat, primarily associated with the monohydrate form (as compared to say, a chelation with malate salt, which typically has not produced the same effect).
Caffeine has not been shown to lower PCr levels inside of the cell to my knowledge - if such evidence exists, please show it. If that was true, every time I had a caffeine source (or presumably, one of the dimethyl metabolites), I would wipe out the naturally occurring PCr that my body continually generates (low levels of PCr are normal). Of course, there is still no medical evidence that this occurs... I think the confusion comes because caffeine, as a stimulant, stimulates everything - including your kidneys & bladder - and does cause increased urination.