Protein is essential for the body to repair cells and promote new cell growth. When you eat protein, it breaks down into amino acids that continually supply the cells that make up your skin, muscles, glands and other body tissues. The body makes some amino acids itself, but must obtain others through dietary protein sources.
Types
Some sources of protein contain all of the essential amino acids, which are amino acids that the body cannot produce on its own. Other dietary sources of protein contain only some of the essential amino acids or they are low in one or more of them. At one time, nutritionists called these complete and incomplete proteins. However, as of the time of publication, not many nutritionists use these names because eating a variety of "incomplete" proteins can still supply all of the protein and amino acids you need.
Sources
Proteins from animal products often contain all of the amino acids the body needs from dietary sources. The best sources are lean meats, poultry, fish, eggs and low-fat dairy products. These items provide protein while minimizing calories and fat. Other sources of protein include dry beans, soy products, legumes and nut products, such as peanut butter. Vegetarians and vegans should try to include as many of these foods in their diets as possible to prevent a protein deficiency from not eating meat and animal products.
Amount
The recommended dietary allowances of protein vary depending on gender and age. Children between the ages of 1 and 3 need 13 g of protein daily. The number increases to 19 g for children between 4 and 8 years old, and to 34 g between 9 and 13. Girls ages 14 to 18 need 46 g of protein daily, while boys of the same age group require slightly more at 52 g per day. Daily protein levels for females don't change after age 18, but men 19 and older need 56 g of protein per day. Some people may require more or less than the RDA, especially if they suffer from liver or kidney problems.
Considerations
Most Americans get adequate amounts of protein through their daily diets. Diets that include high amounts of protein and a low number of carbohydrates are popular for weight loss. While these diets often do lead to significant weight loss, it can be difficult to maintain the reduced weight once you resume a normal diet. Eating high levels of protein is safe for most people on a short-term basis, but talk to your doctor before significantly altering your diet in this way. Not eating enough carbohydrates can result in a fiber deficiency, leading to constipation, diverticulitis and other health problems. A diet high in protein may result in liver or kidney problems, particularly if followed for long periods.
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