Protein is the building block of all life.
Your body needs proteins to survive. The average adult needs around 45-65 grams of protein a day. Protein deficiency can lead to serious problems.
People use protein supplements such as Whey Protein or Soy Protein to increase the protein content in their diet, especially vegans/vegetarians and weight-lifters/athletes.
However if your body doesn't need protein to build muscles (because you aren't exercising enough or are OVER-supplementing with protein) it will quickly turn to fat which is something you need to consider, in addition to consulting with your primary care physician to make sure your kidney and liver function is OK and can support the extra workload a protein supplement will be giving them!
Read this page for more info: Protein (nutrient) - Wikipedia, the free encyclopedia