HOWEVER, bare in mind that everything has it's limits, EVEN proteins.

i'll paste this from a website.

In addition, eating protein at the expense of vegetables, grains and other healthy foods can deprive your body of essential nutrients. Plus, it can cause dehydration because it takes a lot of water to eliminate extra protein.

Excess protein also has been linked to bone loss because the more protein you eat, the more calcium you excrete, for reasons scientists don't fully understand.

A study conducted in 1998 at Creighton University in Omaha, Neb., concluded, however, that people who eat excess protein probably can prevent bone loss by consuming adequate calcium -- or 20 milligrams for every gram of protein. Since bone health depends on a balance of adequate levels of protein and calcium, the best way to avoid bone loss is to eat the right amount of protein for your weight and consume at least 1,000 milligrams of calcium daily.
but since we're dealing here with OP who assumingly boxes 3-5 times a week... but please, bare in mind, i wouldn't say that this is what protein does. there is also vast majority of vitamines that can lead to hyper-vitaminosis in excessive use. if you keep everything in limits, you're fine.

Eating too little protein means your body can't perform all the functions for which protein is required, at least not at peak levels. Over time, you may feel tired and sluggish, be more susceptible to illness, and fail to build muscle or improve your athletic performance at the rate you otherwise would. You also may lose bone. At highest risk are women on low-calorie diets (less than 1,200 calories a day), competitive athletes who restrict calories and burn protein instead of fat, and vegans and macrobiotic diners who don't get enough of the amino-acid building blocks needed to synthesize complete proteins.
...In fact, protein expert Dr. Peter Lemon recently concluded that exercise more than doubles your need for protein.
Too much protein isn't the only problem with the popular high-protein
diets. All there are also loaded with fat, while Dr. Atkins' and Protein
Power are so low in carbs it's hard to fit in enough fruit, vegetables
and whole grains to lose weight healthfully and keep it off.
so it's quite important that you don't just go to the nearest fitness shop and buy the cheapest protein out there. Hopefully people from this forum who use it know which ones are better than the others.