The following information is kind of neat, so if you are even slightly interested, I suggest to just keep on reading. I'll keep it quick.
I would guess that most people think of building muscle, or following the rules of some fad diet when you hear about eating protien. The first thing to consider is what is protein used for in the body? Yes, of course it is used for muscle, but how? Well, the body will break down the protein into the smaller amino acids that make it up, and use those amino acids to repair broken down muscle tissue throughout the body. Muscle tissue breaks down every day from normal activity, such as walking, bending, and lifting even normal things around the house, such as kids and laundry. But protein is also used for much more. Some of the amino acids are used to repair and build tissues other than muscle, such as organ tissue and connective tissue. Proteins are also used in the blood to control fluid balance. For instance, if you do not have enough protein in your diet, then the body will rob it from all sources in the body, and when the blood and cell proteins get too low, then they cannot hold the fluid within the blood and cells and the fluid then moves from the blood and cells and accumulates within the abdominal cavity. This is most noticeable in the malnurished children in Africa, etc, giving them that recognizable larger belly.
NOW, how does protein help you from getting the cold. All cells are made up of protein, escpecially white blood cells, which are the cells that fight off germs, such as viruses and bacteria. The body will "steal" protein from all sources within the body equally when it needs to repair muscle and tissue, which happens every time to go to sleep. So without enough protein in the diet, the body will steal protein that should be going to making new white blood cells and use it to repair muscle, and your body will run low on WBCs. And if you are exercising on a regular basis and breaking down a great deal more muscle tissue, then you run the risk of running low on white blood cells very quickly. Think about it, did you ever ask yourself, why is that person sick all the time, they workout every day???
Good sources of protein: meat, beef, fish, chicken, dairy, beans, nuts, whey protein powder
One more....I cant' help it. Eating protein causes the release of glucagon from the pancreas, which is the hormone that counteracts insulin, and keeps the blood sugar very stable. This will keep you feeling very good, with constant energy, and a stable blood sugar puts the body in a fat burning position all day long.
Thanks for reading, and if you have any questions, please let me know.