Proteins are essential nutrients for the human body. They are one of the building blocks of tissue and can be used as a fuel source (although this happens as a backup when the body doesn't get enough carbs from the diet). As fuel, proteins can provide as much dense energy as carbohydrates, but the most important aspect of protein quality is the amino acid composition. Proteins are formed by chains of amino acids, think of it like a chain link chain. If you have a long chain you can do a lot with it, although if you have short one you can't do much with it. Same for protein sources, the body can use more of the protein if its a high quality source. There are nine essential amino acids that humans must have in order to sustain life. These amino acids are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. When deciding on your diet, you should consider how your protein sources rank on the NPU scale.
Net Protein Utilization or NPU is the ratio of amino acid converted to protein to the ratio of amino acids supplied. Going back to the chain reference, the longer the chain the higher quality the protein. In short, this means that if you eat 10 grams of protein, is your body able to use 5 or 7 of those grams? As a value NPU can range from 1 to 100, 100 meaning you use every bit of the protein supplied. For reference, the incredible edible egg has an NPU of 98. If you're curious about a food source, try googling the NPU of that source of food to see where it scores.
So what does all this really mean for you? It means that the type of protein you put in your body is just as important as the amount of protein. You can use both of these factors to judge just how “good” the protein you are consuming is for you.
Considerable debate has taken place surrounding protein intake requirements. The amount of protein in a person’s diet is largely influenced by overall energy intake, physical activity level, energy and carbohydrate intake, as well as the presence of illness or injury. Strenuous exercise as well as increased muscle mass boost the need for protein and the need is increased to promote healing after injury or surgery.
Consult your doctor or a fitness professional who can look at your lifestyle and body type to learn what your protein requirements are, and make sure they have a high NPU!