Creatine is a nitrogenous organic acid that occurs naturally in animals and helps to supply energy to all cells in the body, primarily muscle. This is achieved by increasing the formation of Adenosine triphosphate (ATP).
Due to the ATP production, creatine would be expected to have an impact on increasing energy production in exercise lasting between 10 seconds and 2 minutes.
Creatine is naturally produced in the human body from amino acids primarily in the kidney and liver (about 1 gram per day). It is transported in the blood for use by muscles. Approximately 95% of the human body's total creatine is located in skeletal muscle.
Creatine is not an essential nutrient, as it is manufactured in the human body from L-arginine, glycine, and L-methionine.
Creatine improves brain function, has a positive effect on strength increase individuals with neuro-muscular disease, as well as increasing LBM and strength in trained healthy individuals.
Creatine causes an increase in certain hormonal regulators/gene expression of muscle tissue (Not anabolic signalling. Meaning no direct effect on protein synthesis). That can leads to an increase in LBM.
Creatine causes intramuscular water retention (which is also one reason why LBM increases) and another reason why strength is increased (as it the water is an essential part to the energy production cycle).
It does not cause the bloat that is normally associated with creatine supplementation. The key point being the excess carbohydrate intake and associated sodium increase is the reasoning behind the 'bloat'.
The negative effect on hydration that is often stated with creatine supplementation is also another myth. Most individuals will often have an inadequate water intake and poor electrolyte balance, that will lead to the cramping and hydration issues that have been blamed on creatine.
Creatine dose is generally done in a loading phase of either 20 grams for 5 days or 10 grams for 10 days. Typically that is then followed by a maintenance phase of 5 grams daily. Over time regardless of what loading phase you choose, if you do choose to load, your muscular creatine saturation levels will be eventually at 100%. Timing of creatine intake/consumption is irrelevant to achieving the benefits from creatine supplementation. Take whenever and however it suits you.
There are many different forms of creatine available on the market today, all of which are the typical creatine monohydrate with a different carrier molecule attached. Creatine Ethyl Ester, Tri Creatine Malate, Creatine Nitrite and the list goes on and on. All those forms of creatine claim to be the 'best' form available and more gains blah blah blah. Well in all studies done on these 'superior' forms of creatine, the have performed no better than (if not worse) creatine monohydrate. They are just another marketing gimmick that is simply trying to reinvent the wheel and offering no further benefit other than 3 times the price!
On a side note creatine can be taken in any form of liquid except Citrus juice/fruit as the conversion to createinine will occur and therefor make the creatine unusable. Createinine is a by-product of creatine breakdown with in the muscle tissue. Createinine will be filtered out by the kidneys and there is little to no re-absorption.
There are about 20% of people who are non responders to creatine supplementation. Why? Well it is not completely known but it would have to be something to do with the mechanisms involved in uptake. It seems responders have have the lowest starting creatine levels, a higher proportion of Type 2 muscle fibres, a larger muscle cross sectional area and a larger amount of LBM. Non-responders had the opposite characteristics.
Amount of benefit? well that is hard to pin point as there are many other intangibles and variables that effect training performance/ability/muscular hypertrophy. You may get an extra ~5% out of your training over time if you are doing EVERYTHING else right.
Final word, Creatine IS NOT a steroid.
Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial.
Does Creatine Supplementation Hinder Exercise Heat Tolerance or Hydration Status? A Systematic Review With Meta-Analyses
Effects of creatine supplementation and ... [J Strength Cond Res. 2003] - PubMed - NCBI
Effects of creatine on isometric bench-... [Med Sci Sports Exerc. 2002] - PubMed - NCBI
Effects of creatine supplementation and ... [J Strength Cond Res. 2007] - PubMed - NCBI
Effects of oral creatine supplementatio... [Med Sci Sports Exerc. 2000] - PubMed - NCBI
Effect of different frequencies of creat... [J Strength Cond Res. 2011] - PubMed - NCBI