Protein is the major structural component of all of our bodies' cells, tissues and organs. It is also an integral portion of hemoglobin, hormones, membranes, transport carriers and enzymes that catalyze chemical reactions necessary for normal body functioning. Our body's protein structures are consistently being broken down and need to be replaced with the protein that we get through our diet. Proteins are made up of amino acids, referred to as the building blocks of protein. There are approximately 20 amino acids that our bodies can use to make proteins.
Recommended Daily Protein Intake for Adults
The Instistute of Medicine has established a recommended dietary allowance for healthy adult men and women of a minimum of 0.8 grams of high-quality protein per 1 kilogram of body weight. For an adult who weighs 160 pounds, this is equivalent to 64 grams of protein a day. This recommendation is based on decades of research from studies that analyzed nitrogen balance in adults.
Recommended Upper Range for Protein Intake
There currently is no tolerable upper intake level for total protein or individual amino acids regarding specific amounts in terms of total grams per day due to insufficient data. However, the Institute of Medicine has established an upper range for total protein intake at 35 percent of total daily calories to reduce the risk of chronic disease. The majority of adults in the United States get ample protein, but in many parts of the world people do not consume enough protein.
Food Sources of Protein
A complete source of protein, also known as a high-quality protein, provides all of the essential amino acids, which are the amino acids that our bodies cannot make and must obtain through food. Foods of animal origin, such as meat, poultry, fish, eggs and dairy products, are complete proteins.
An incomplete protein source is lacking one or more of the essential amino acids. You can pair two or more incomplete proteins that, when combined, provide all of the essential amino acids. These sources of protein are called complementary proteins. Most proteins that are of plant origin are incomplete proteins, with the exception of soybeans, which are a plant-based complete protein. Aim to get adequate protein from a variety of sources.
Special Considerations
Some groups of people may need less protein than the average healthy adult. Certain medial conditions can decrease the recommended amount of daily protein intake. For individuals who have diabetes or early-stage kidney disease, protein intake needs to be limited to 0.8 to 1 gram of protein per kilogram of body weight, as recommended by the American Diabetes Association. This is recommended to help preserve or improve kidney function in those individuals.
References
- Centers for Disease Control and Prevention: Nutrition for Everyone -- Protein.
- Harvard School of Public Health The Nurtition Source Protein: Moving Closer to Center Stage.
- Institute of Medicine of the National Academies Food and Nutrition Board: Dietary References Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients).
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