The vast majority of negative side effects associated with too much protein have their roots in the kidneys' circulatory system. While there are those that dispute these health complications, many argue that, first of all, excess protein that cannot be absorbed by the body causes increased production of urea in the urine, and this can lead to a variety of different side effects all over the body. The mechanism for producing urine in the body is the kidneys, so the increased workload may increase the risk of kidney disease and the worsening of any kidney problems that already exist. More indirectly, this process can increase one's risk of gout, and the frequent urination, as a result, can lead to dehydration. In addition, calcium tends to be excreted in the urine in conjunction with the excess urea, and some researchers have argued that this can increase one's risk of osteoporosis and kidney stones.
More specifically, the reason why too much protein leads to higher concentrations of urea in the urine is because excess protein gets relegated to the liver, where the animo acids will be converted into other usable molecules through a process called deanimation. During the process, nitrogen from the animo acids is transformed first into ammonia, and then into urea by the liver. Excreting this through urine is the job of the kidneys, but too much protein in the diet poses a heavy workload for these organs. Those who already have some form of kidney disease are best off keeping their protein intake at a stable level.
Gout is a form of inflammatory arthritis that is characterized by a buildup of uric acid in the joints. Some argue, then, that consistent excess protein in the body increases one's risk of gout. The kidneys are normally instrumental in expelling uric acid from the body, but the extra workload imposed on them may impair this function.
More frequent urination is the obvious side effect of the above biological process. Each time an individual urinates to expel the extra urea, water will inevitably be excreted as well. As a result, too much protein can quickly lead to dehydration, which may be indicated by symptoms such as headache, muscle cramps, or dizziness.
Furthermore, the excess levels of urea produced during this process will normally lead to an unstable pH level. Researchers have observed increased concentrations of calcium in the urine of those with too much protein in their diet, and some believe that said calcium exists to balance out pH levels. Although there is some dispute, this may pose a risk for osteoporosis because the body may reabsorb calcium from the bones for this purpose. Some believe that increasing one's calcium intake can compensate for this. In addition, the higher concentrations of calcium circulating through the kidneys may increase one's risk of kidney stone formation.