Every human being needs protein every day in order to live. Protein is a basic component of life. Just how much protein do you need?
It all depends on who you talk to. If you talk to vegetarians, they of course say that you don't need any animal protein at all. If you talk to most scientists, you get a different story. Part of the problem is that we still are just learning about how proteins work in our body.
The US RDA is the US science's best guess about *minimum* values for any given nutrient. They say it's about .4g of protein for every pound of weight. So if you were a 100 pound person, you'd need about 40g a day. If you were a 200 pound person, that would be 80g a day, and so on.
If you don't eat that much protein in a given day, your body has to find it from somewhere. Your body actually begins to *take* protein away from your muscles. You don't have to be a bodybuilder for this to be really important. Every human needs to be able to move around, to use their hands, and so on. If your muscles begin to atrophy, it makes everything else much harder.
So first, it's important to realize that you need that daily protein, in whatever form you choose to take it. Second, you move on to what TYPE of protein. Protein is a generic name for a group of amino acids. Remember this from biology? It's like saying you need to take vitamins - but then saying you need X amount of Vitamin A, Y amount of Vitamin C and so on. With proteins, these amino acids are listed below, with the adult RDA daily amounts per pound of weight.
Methionine & Cystine 5
Phenylalanine & tyrosine 8
Science is still figuring out how much protein we need, how much of each amino acid we need, and how this all works. Most of our ancestors were hunters, eating turkey, deer, and other wild animals. It was a normal part of life. In modern times we eat caged chickens and quarter pounders with cheese - so how can we equate this?
Still, in those days it was very hard to hunt meat - and tribes shared it so each person got a reasonably small amount. In modern times, we just drive up to a door and get good servings of protein.
For example, if you just get a Grilled Chicken Caesar Salad from McDonalds, you're getting 17g protein. A Quarter Pounder with Cheese is 28g of protein. Still, keep in mind that if you're aiming for 80g in a day, you haven't quite made it yet. Be sure to keep track of the protein you eat each day, to aim for a balanced amount in your diet.