Protein is an essential nutrient for your body and has many function including cell maintenance and repair. Literally every single cell in your body requires it to repair, grow and maintain itself. The amount of protein that you require will depend on primarily on your activity level; The more active you are the more you will need so that your muscles can recover and grow new mass. Also if you have fallen ill you will require more to recover.
A complete protein is made up of amino acids, which are like the building blocks of proteins. An easy way to imagine this is to think of a house as a protein, and the bricks as the amino acids – only once all amino acids (or bricks) are in place, the protein (or house) is complete. There are 22 amino acids of which 8 are called essential because they must be consumed by our diet. The other 14 amino acids can be made in the body by using the other 8 essential amino acids.
So how much do you need? The accepted figure is roughly 0.8g per kilogram of lean body mass for an adult. However if you want to gain muscle mass you will need to eat about 2g per kilogram of lean bodyweight. Again the recommended figure for protein take for normal adults is about 15% of caloric intake, but this shoots up to a massive 40% when trying to build muscle mass. It is vitally important to consume enough when looking to build muscle mass; If you do not eat enough you will not be able to pack on slabs of lean muscle.
The best source of protein are lean meats such as chicken, turkey, fish such as salmon and salmon, red meat and eggs in addition to protein supplements such as whey protein. These sources will contain complete proteins (22 amino acids). Other foods such as carbohydrates sources like pasta, couscous and beans will contain protein but not complete protein so it is vital to try and supplement your diet with a protein supplement such as soy protein or whey protein if you are vegetarian.