Feedback about creatine often seems mixed. Many love it, but many also report problems. Just in this thread there are people talking about heart palpitations and sleep problems. I have the theory that these side effects and mixed experiences come from impurities of lesser quality products. Apparently there are mostly two sources: Creatine mono-hydrate which mostly comes from China and "creapure", which is a patented formula known for its purity. Does anyone have insight into how substantiated this theory is? How likely are negative effects because of pollutants/impurities?