Research shows that eating protein helps build muscle and, in some cases, burns fat too. There are almost certainly other yet-to-be proven benefits. We just don't know what they are yet. As the scientific story unfolds, it's becoming increasingly clear that different proteins offer different benefits, so try to work in as many different types as you can.
A QUICK LOOK AT THE DIFFERENT TYPES
1) Whey Protein
The undisputed king of proteins. Here's why: whey proteins are quickly and easily digested (hence the "fast-acting" description that they are often given), they are loaded with Essential Amino Acids (EAA's) - including the three Branched Chain Amino Acids (BCAA's), and they contain subcomponents (microfractions) that appear to provide benefits above and beyond amino acids and elemental nitrogen. Whey proteins are available in several forms. The most basic is whey concentrate. Whey protein isolates have much of the fat, lactose and other undesireable elements "isolated" out. Whey peptides have been hydrolyzed, or broken down, for even faster digestion. So the purest and fastest digesting whey proteins you can buy are hydrolyzed whey protein isolates.
2) Casein Proteins
About 80% of the protein in milk is casein. Often referred to as a "slower-acting" or "time-released" protein because it is digested and absorbed much more slowly than other proteins, casein proteins are especially useful when taken at bedtime and during other prolonged periods without eating.
3) Egg Proteins
Ask any dietitian, "What's the best source of protein?" and eggs will probably top the list. Most nutrition textbooks refer to eggs as the "gold standard" for protein quality. With loads of EAA's and some of the highest scores of protein quality, we're not going to argue. Naturally dairy-free eggs are a great alternative to whey caesin and whole milk proteins for those with milk allergies or severe lactose intolerance.
4) Blended Proteins
If you can only afford one type of protein, consider going with a blend. Combining faster, intermediate, and slower protein sources, blended proteins give you more sustained protein digestion than single source proteins like whey, casein, or egg.
5) Recovery Proteins
There are moderate calorie, fast-acting protein and carbohydrate combinations specifically designed to be consumed immediately after workouts when nutrient needs are great and glycogen and muscle protein resynthesis are at their peak. Many also contain whey protein hydrolysates and supplemental ingredients like creatine, BCAA's, and glutamine to further aid in the recovery and rebuilding process. This may also include complementing ingredients like, creatine, betaine and micronized amino acids to assist with your muscle building goals.