The Facts about Protein in the Diet
The Roles of Protein in the Body:
Proteins are very diverse molecules, serving many different functions throughout the body. Protein provides structure and plays important roles in regulating body functions. Dietary protein can also be used to meet the body’s energy needs, but is not the preferred energy source.
Protein provides the structural component for the major body tissues such as hair, skin, heart, and skeletal muscle. Along with providing muscle structure, protein is also heavily involved in the mechanics of muscle contraction.
Additionally, proteins play many diverse roles in regulating our body functions. For example, hormones, enzymes, antibodies, and blood transport molecules are all composed of protein.
As mentioned, protein can be used for energy, but normally carbohydrate and fat are the preferred energy sources. Because protein is required for so many structural and regulative functions, the body typically spares protein for those functions in lieu of being broken down for energy.
Protein Requirements:
Our bodies are constantly breaking down and building new protein molecules. Due to this process, we lose a certain amount of protein on a daily basis. The Institute of Medicine has determined recommended daily protein intakes based on these estimated protein losses. For a healthy individual, the current Recommended Dietary Allowance (RDA) for protein is 0.8 gram per kilogram of adult body weight. For an average adult male weighing 160 pounds (79 kg), this translates to 63 grams of protein per day and 45 grams of protein per day for a typical woman weighing 125 pounds (57 kg). This is much less than what the average American typically consumes – 70 grams/day (women) and 100 grams/day (men).
Another way to represent protein requirements is as a percent of total caloric intake. It is recommended that your total caloric intake be derived from 50-60% carbohydrates, 10-15% protein, and 25-35% fat. In other words, a person consuming 2,000 calories per day would want to eat approximately 50-75 grams of protein. Following is an example of how to calculate the approximate grams of protein you need in a day based on a 2,000 calorie diet:
Example: 2,000 calories x 10% = 200 calories. There are 4 calories in 1 gram of protein. 200 calories divided by 4 calories per gram of protein = 50 grams protein.)
Determining your protein needs based on the percent of calories consumed is much easier for most people to calculate and is what is provided on a the Nutrition Facts Panel.
Protein Sources:
Each type of protein is made up of as many as 20 different amino acids connected together in a specific combination and order. Of the 20 different amino acids found in the human body, 9 are considered “essential” amino acids. Essential amino acids cannot be made by the human body, thus need to be consumed in the diet. Animal-based protein (protein derived from meat, dairy, fish, seafood, and eggs) typically contain all of the essential amino acids in one or two servings of the food. Protein derived from plant sources typically does not contain all of the essential amino acids in one food serving. For that reason, vegetarian diets need to be balanced in such a way as to provide all of the essential amino acids within a 24 to 48 hour time period.
Conclusion:
It is best to consume protein in the range of 10-15% of total calories. If you eat animal-based protein, try to get your protein from both animal and plant sources. Some excellent plant sources include legumes such as lentils, black beans, soybeans, pinto beans, tofu, nuts, and seeds. Grain products such as bulgur wheat and oatmeal are also good sources of protein. If you consume animal-based products, choose low-fat cuts of
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