As body builders, figure competitors or participants in a sport, we consume a good amount of protein; to adequately feed our muscles. However, is this safe and will it have any adverse side effect, long term. I have done a modest amount of research on this subject and although I haven’t read every article and research paper this is what I have come up with.  
Proteins are vital to our bodies and are necessary for our body structure and proper function. They function as enzymes, hormones and antibodies. High protein diets have been popular since the early 1960’s, has been proposed as the “new strategy for successful weight loss”. The weight loss that occurs initially is high as a result of the fluid loss that is directly related to the reduction of carbohydrate intake, calorie restriction and “ketosis induced appetite suppression” These diets typically offer a wide variety of protein food alternatives, well thought-out eating plans and are somewhat limiting in others, mainly (the “stuff” we all know and love), carbohydrates. It has been suggested that for most healthy individuals, these diets may not be harmful over a short period of time; however there are no long-term scientific reports to substantiate its overall “safety and efficacy”. (Sachiko et al, 2001)  
According the AHA (American Heart Association) they state that diets that are high in protein are not recommended because “they restrict healthful foods that provide essential nutrients and do not provide the variety of foods needed to adequately meet nutritional needs.”  They also state that “individuals who follow these diets are therefore at risk for compromised vitamin and mineral intake, as well as potential cardiac, renal, bone, and liver abnormalities overall.” (Sachiko et al, 2001)  
In terms of safety issues, there is little long term information that is available (at least in the studies that I have read on the health effects of high protein consumption in our diets. From the data that is available there is evidence that “consumption of protein greater than two to three times the U.S. RDA will contribute to urinary calcium loss and may predispose to bone loss” later on down the road.  Individuals that are predisposed to nephrolithiasis (kidney stones), kidney disease and individuals with Diabetes Mellitus are cautioned.  (Eisenstein, Roberts, & Saltzman, 2002)
Works Cited

Eisenstein, J., Roberts, S. B., and E. Saltzman,   "High-Protein Weight-Loss Diets: Are They Safe and Do They Work? A Review of the Experimental and Epidemiologic Data." Nutrition Reviews 60 (2002): 189-200. 26 July 2007 <http://www.ingentaconnect.com/content/ilsi/nure/2002/00000060/00000007/art00001>.

St. Jeor, Sachiko T. , Howard, Barbara, V.  Prewitt, Elaine, Bovee, Vicki, Bazzarre, Terry and Eckel Robert H.
Dietary Protein and Weight Reduction: A Statement for Healthcare Professionals From the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association
Circulation, Oct 2001; 104: 1869 - 1874.