Excellent question! Health and fitness magazines are filled with ads for protein powders, shakes, etc. You can buy soy protein, milk protein, whey protein, etc. First off, what is protein and why is it important for health and fitness? Protein is composed of chains of amino acids, the building blocks of our muscles and tissues. We need to eat protein to rebuild damaged muscles from working out (that's a good thing), maintain muscle mass, and keep our bodies in top health. Protein is very useful for dieters because protein makes us feel full. A meal including protein will keep you full much longer than a meal of just carbohydrates - it increases our feeling of satiety because protein takes a longer time to digest. Great sources of dietary protein include lean meats like poultry, fish, shellfish, extra lean red meats, beans, legumes, nuts, soy, and low-fat dairy products. So, where does protein powder fit in? Protein powder is useful for bodybuilders who need to consume a lot of protein to build really big muscles, and it's hard for them to get enough protein without supplementing occasionally. Protein powder is a supplement, folks, not a substitute! Though protein powder may contain added vitamins and minerals, it is not a substitute for real food. Real food contains many beneficial components like vitamins, minerals, fiber, and antioxidants. It is best to get most of our protein from "real food." However, protein powder does have its uses. For example, protein powder can be used to supplement "real food" like breakfast fruit smoothies, instant oatmeal, and other carb-laden food that needs a protein boost to keep you full. The Science Lady likes to take protein powder along while on multi-day backpacking trips, as hiking for 8+ hrs per day requires a lot of protein for muscle recovery, and when you have to carry it all on your back, protein powder helps!
As for choosing a protein powder, just choose one you like that dissolves easily. None of them contain magic, secret ingredients, no matter what the ad says. Those glossy ads are all designed to sell you a product! Also, check out this helpful article on About.com about protein powder for more info: http://bodybuilding.about.com/od/bodybuildingfaq/f/protein_drinks.htm