Protein is an essential part of everyone's diet. Protein molecules are long chains made up of amino acids, and protein is necessary for your body to be able to build and maintain muscle mass, make red blood cells and produce hormones. While it is absolutely necessary for each of us to get enough protein in our diets, it is also possible to consume too much protein. Making sure you get the right amount of protein is a key part of being healthy.

Current Guidelines

The current version of Dietary Guidelines for Americans recommends that 15 percent of an adult's total caloric intake should be protein. This means that an adult who consumes 2500 calories a day should consume 375 calories of protein. Some nutritionists recommend a protein intake of 20 percent of total calories, so the same person would need to eat 500 calories of protein a day. These guidelines work very well for adults who are eating an average number of calories daily. However, the guidelines do not work for everyone.

Limitations

The current guidelines that make protein intake a percentage of daily caloric intake do not work well for people who are eating reduced-calorie diets for weight loss, or because of loss in appetite due to aging or illness. Adults need a certain amount of protein in relation to their body weight, regardless of how many calories they eat, in order to maintain a good amount of muscle tissue for their size. The recommended daily allowance (RDA) of protein is 0.8 g/kg/d, which means that a person should eat 0.8 grams of protein for every kilogram (2.2 pounds) he or she weighs. A woman who weighs 220 pounds and goes on a diet to lose weight should not eat less than 80 grams of protein a day; if she eats less than this, she is at risk for losing muscle mass. Protein is also very important for making you feel satisfied after you eat, so it can help dieters eat fewer total calories. And muscle mass burns calories, so a person who loses muscle mass by dieting will actually become less able to burn calories and more likely to gain weight back.

Bottom Line

If you are an adult of normal weight and you eat 2000 calories or more a day, then making sure that 15 to 20 percent of those calories come from protein is a good guideline. If you are obese, are on a restricted-calorie diet or don't eat very many calories due to loss of appetite, then you are much better off making sure you eat 0.8 grams a day for every kilogram you weigh, which is 0.36 g for each pound. You can use a calculator to multiply your weight in pounds by 0.36, and make sure you eat at least that many grams of protein a day. Most food packages include nutrition information and resources such as nutritiondata.com have the protein content for most foods. Make sure you spread your protein intake evenly among your meals instead of eating most of your protein in your biggest meal of the day, to keep your metabolism going and to keep yourself feeling full. If you are an athlete, loading up on expensive protein supplements is a waste of money; 20 percent of your total calorie intake is plenty of protein for you to build muscle if you are not restricting calories.

Source:

Rice University: "Protein Requirements for Athletes- Meeting your Meat Needs" by Caryn Jenky

Layman, Donald K. "Dietary Guidelines should reflect new understandings about adult protein needs" Nutrition & Metabolism 6. 12 (2009).

Ask the Dietician: Protein and Amino Acids

Resource:

Ask the Dietician: Healthy Body Calculator

NutritionData.com