I recommended a client to start out with whey protein and creatine monohydrate after 6 months of weight-training and solid food. Two days later, he sent me this article below and a quote "I'm not taking this shit."

Dangers of Creatine - Bad Effects of Creatine

Creatine is nitrogenous organic acid occurring naturally in all vertebrates. Creatine helps to supply energy to muscle and nerve cells. The body manufactures stores and uses creatine for pursuits which require bursts of energy like running at a high speed. An average person weigh 150 lbs has the ability to manufacture around 120 grams of creatine, and uses up around 2 grams of creatine in daily pursuits. Creatine can be classified as a dietary health supplement, as one can consume, theoretically, enough creatine rich food like red meat, to substitute supplementation.
Though creatine is a protein which occurs naturally in the body, and has been classified by manufacturers and sellers as devoid of side effects, increasing creatine content within the body is not entirely free of short and long term problems which the user might suffer from.

Creatine has been known to cause mild to serious side effects among users. Its use may lead to cramps, stomach upsets and vomiting. Also, due to its property, Creatine absorbs water from cells which results in increasing the water mass of muscles, leading to dehydration, and obesity. Physicians are of the opinion that due to this dehydration, users may suffer from mood swings, increased anger and depression. In fact users have claimed that depression levels dropped among them when they stopped taking creatine. Users are thus advised to drink lots of water to stop dehydration.

Among serious side effects creatine causes kidney, and gastrointestinal disorders. Users have also reported increased anxiety, acne, male breast formation (Gynecomastia), and a reduction in penis size and hair loss. Gastrointestinal complications have been commonly reported among users of creatine supplements. Moreover, scientific studies have proved that increase in body mass from creatine use can be attributed to water retention by muscle.
Creatine use among health freaks is still under a lot of debate. Critics have claimed that the Loading Phase involves a lot of creatine intake, which the body is unable to process. This leads to excretion, and thus wastage of creatine. Moreover research on the benefits of creatine has been limited both in terms of number of research reports and duration of research questions as to how creatine affects teenaged users, elders and pregnant or lactating mothers have remained unanswered due to lack of conclusive research in this field. It is important to note here that not all creatine supplements have obtained the FDA approval. FDA approval to Creatine is termed as "loose" by many industry experts, since though creatine is approved, a lot of marketers add more chemicals to pure creatine to lessen side effects and increase effectiveness. For example, one seller alleges that its product does not get converted to creatinine in the human stomach, a compound which is nullify all expected benefits from ingesting creatine. The company claims that it does this by addition of chemicals to prevent conversion of creatine into creatinine. The effects of such additives on the human body haven't been studied. Users are thus advised to always consult a doctor before taking creatine.

http://www.creatine-monohydrate.org/...f-creatine.htm