Creatine and protein supplements are commonly taken by weightlifters to promote muscle growth, provide energy and improve performance. The amino acid creatine, in particular, may possibly benefit athletic performances of young, healthy people, involving short bursts of intense exercise such as sprinting or weightlifting, according to MedlinePlus. However, as dietary supplements including creatine and protein are associated with certain health risks, you should not take creatine or protein supplements without your doctor's approval.
Neither MedlinePlus nor the University of Maryland Medical Center cite protein as interacting with creatine in a harmful way. The only dietary contraindication for creatine is caffeine, which has been associated with serious adverse effects when consumed in large doses with creatine and the stimulant ephedra. Nevertheless, it's important to exercise caution when taking creatine with protein supplements as both substances can lead to dehydration and possibly harm the kidneys when taken in excessively large amounts or with insufficient water. People with preexisting kidney disease should not take creatine or follow a high-protein diet.
While there isn't conclusive evidence indicating a harmful interaction between protein and creatine when both substances are used by healthy individuals and as directed, limited research suggests this combination may, indeed, harm healthy young people. Specifically, a case report published by "Seminars in Liver Disease" in 2008 presented a case of a 27-year-old man with acute liver damage associated with the combination of whey protein and creatine supplements. Another case study, published in "Journal of Renal Nutrition" in 2006, presented a case of acute renal failure and proteinuria -- excessive protein in the urine -- in a 24-year-old taking creatine and other bodybuilding supplements.
Although the combination of supplemental protein and creatine may present certain health risks, this combination may also confer athletic benefits when taken with carbohydrates in the context of an exercise program. According to the University of Illinois, taking creatine after exercise with a protein and/or carbohydrate supplement may increase creatine's therapeutic benefit of increasing creatine stores in muscles. A study published in "Medicine and Science in Sports and Exercise" in 2007 concluded that a combination of creatine, protein and carbohydrates promoted muscle hypertrophy, or increased muscle cell volume, in resistance-trained subjects.
It's important to note that creatine and protein do not provide athletic benefits for everyone. If you already have high creatine stores in your body, taking supplemental creatine will not provide any additional benefit as the body can only store a limited amount of this substance. As a typical American diet including meat, poultry and fish supplies generous amounts of both protein and creatine for athletic needs, a vegetarian athlete is more likely to benefit from taking creatine and/or protein supplements compared to a non-vegetarian. Moreover, creatine does seem to benefit performance in aerobic activities or to benefit older people, notes MedlinePlus.