• Protein is a vital nutrient that plays several roles in the body. It transports nutrients in the bloodstream, assists in promoting blood clotting and wound healing and aids in fluid, electrolyte and pH balance. Protein also supports the growth and maintenance of lean muscles, bones, nails and the crucial heart muscles. Protein needs vary by person depending upon age, weight, sex, activity level and overall health. In general, it's recommended that 10–35% of your daily calories come from protein.
  
  Here are examples of amounts of protein in food:
  • 1 cup of milk has 8 grams of protein
  • A 3-ounce piece of meat has about 21 grams of protein
  • 1 cup of dry beans has about 16 grams of protein
  • An 8-ounce container of yogurt has about 11 grams of protein
  
  Added together, just these four sources would meet the protein needs
  of an adult male (56 grams). This doesn't count all the other foods
  that add smaller amounts of protein to the diet. Most Americans
  get more than their needed protein daily. Rather than just focusing
  on your protein needs, choose an overall healthy eating plan that
  provides the protein you need as well as the other nutrients
  (carbohydrates and fat). Remember that increasing your protein intake
  WILL NOT increase muscle mass by itself.
  
  RECOMMENDED DAILY PROTEIN ALLOWANCE
• Children ages 1 - 3              13 grams
• Children ages 4 - 8              19 grams
• Children ages 9 - 13             34 grams
• Girls ages 14 - 18                46 grams
• Boys ages 14 -18                 52 grams
• Women ages 19 - 70+          46 grams
• Men ages 19 - 70+               56 grams 

 Additional Resources:

http://mypyramid.gov/pyramid/meat.html