Adequate dietary intake of protein is necessary for the body to sustain and repair itself. According to the Institute of Medicine's Food and Nutrition Board, 10 to 35 percent of calories should come from protein, and 2005-2006 National Health and Nutrition Examination Survey showed most Americans are consuming more than enough. On average women are consuming about 152 percent and men almost 182 percent of the recommended dietary intake.
The human body is made up of trillions of cells, each of which contains protein. A combination of 20 different amino acids can make up a protein. Some amino acids can be made in the body but some, considered "essential" amino acids, must be included in the diet. Protein foods that provide all of the essential amino acids are considered complete proteins, and those that lack essential amino acids are called incomplete proteins. Incomplete proteins are found in plant-based foods, such as beans or peanut butter, while complete proteins are found in animal products such as poultry, eggs, fish, dairy products and meat.
Protein's Role in the Body
Proteins are the building blocks of life, and the body needs them to repair and maintain itself. In addition, proteins help make up skin, bones, muscles, organs and a variety of other tissues. During periods of rapid growth, such as pregnancy, childhood and puberty, protein plays a major role in development.
RDAs for Protein
The amount of protein needed by the body can differ based on age, sex and activity level. The recommended dietary allowance for adults over the age 18 is 0.8 grams per kilogram of body weight per day. Each pound is equal to 2.2 kg, meaning that a 150-pound person weighs about 68 kilograms. Therefore, a 150-pound person needs to get about 54 grams of protein per day to meet his or her needs.
Protein Needs for Athletes
For athletes, protein needs may be increased. Needs will vary based on age, sex, amount of activity, body size and fitness level. For endurance athletes, protein intake of 1.2 to 1.4 grams per kilogram per day is recommended, while strength athletes may need 1.2 to 1.7 grams per kilogram per day. For example, a 150-pound endurance athlete may need 82 to 95 grams of protein per day.
Dietary Sources of Protein
Protein is found in poultry, seafood, meat, beans and peas, eggs, nuts, seeds, dairy and soy products. To optimize nutritional health, aim to include a variety of these protein sources in your diet. Also, choose lean sources of protein most often, such as chicken or turkey without skin, lean cuts of beef and pork, leaner ground meats, fish and low-fat dairy.
- Centers for Disease Control and Prevention: Protein
- Institute of Medicine: Dietary Reference Intake, Macronutrients
- USDA ChooseMyPlate.gov: Protein Foods
- USDA Agricultural Research Service: Table 2 Nutrient Intakes from Food: Mean Amounts and Percentages of Calories from Protein, Carbohydrate, Fat, and Alcohol, One Day, 2005-2006
- MedlinePlus: Protein in diet
- Krause's Food and Nutrition Care Process, Nutrition in Exercise and Sports Performance; L. Kathleen Mahan et al.