Protein is essential to human life — every cell in your body contains it. Your skin, bones, muscle and organ tissue all contain protein. It's found in your blood, hormones and enzymes as well.
Protein is also a nutrient found in many foods. Legumes, poultry, seafood, meat, dairy products, nuts and seeds are your richest sources of protein. Grains and vegetables supply small amounts. Remember to choose your sources of protein wisely. Many high-protein foods are also high in fat and cholesterol.
The amount of protein your body needs varies depending on your weight. For example, a 140-pound woman needs about 51 grams of protein a day, and a 175-pound man needs about 64 grams a day — based on the estimated requirement of 0.364 grams per pound (0.8 grams per kilogram) of body weight. However, most Americans typically eat far more protein than they need. Your body stores the extra calories from protein as fat.
Even if you don't eat any animal protein, you can easily get enough protein as long as you include in your diet some protein-packed plant-based foods, such as beans, lentils, tofu or tempeh.
(Source: Mayo Clinic website – www.mayoclinic.com)