By Linda M. Ulerich, RD
We all need protein in our diet every day. Proteins, carbohydrates and fats are the three fuel sources (calories) in the foods we eat. Protein is used to build muscle and fight infection.
How do you know how much protein you need daily? Protein needs vary based on your age, sex and overall general health. The Recommended Dietary Allowance (RDA) for protein in healthy adults is 0.8 grams of protein per kilogram of desirable body weight a day. So, for a 150 pound person (divide by 2.2 to get 68 kilograms then multiply by 0.8), that is 55 grams of protein a day. For someone who weighs 120 pounds, that would be 44 grams of protein a day. If we eat more protein than what our bodies can use in a day, it becomes a source of excess calories, which can cause weight gain. Protein byproducts are removed from the body by the kidneys, which filter it out in the urine.
For someone with declining kidney function, the byproducts of protein breakdown in the body can build up in the blood instead of being cleared out. Many studies suggest that limiting the amount of protein in the diet may slow the loss of kidney function. It is important that a kidney doctor (nephrologist) and a renal dietitian help plan the amount and type of protein sources to be provided in your diet, at even the earliest stages of kidney disease, so that kidney function can be monitored closely for any necessary diet and medicine changes.
Protein sources in our diet come from animal sources and plant sources. Animal sources of protein are considered "complete" or "high quality" protein as they provide all the essential amino acids (the building blocks of protein). Animal sources of protein vary in their amount of fat, with fatty cuts of red meat and whole–milk dairy products and eggs being the highest in saturated fat (less healthy for the heart). Fish, poultry, and low–fat or fat–free dairy products are lowest in saturated fat.
An "incomplete" or "lower quality" protein source is one that is low in one or more of the essential amino acids. Plant sources such as beans, lentils, nuts, peanut butter, seeds and whole grains are examples of incomplete proteins. The good news is that if you eat a combination of these incomplete proteins in the same day, they can provide adequate amounts of all the essential amino acids. Vegetarians can meet their protein needs with careful planning. For example, combining red beans and rice or peanut butter on whole grain bread together make a complete protein. Another bonus with plant proteins is that they are low in saturated fat and high in fiber.
Examples of the amount of protein in the typical serving sizes of the major protein foods:
1 whole egg or 1/4 cup frozen egg substitute = 7 grams
3 ounces cooked meat (size of a deck of cards) = 21–24 grams (leaner meats are higher in protein per oz.)
8 ounces milk (whole, 2%, skim, soy) = 8 grams
8 ounces yogurt or 1 ounce cheese = 8 grams
1 cup cooked beans (navy, pinto, kidney, black–eyed peas, split peas) = 14–16 grams
1 ounce of dry roasted peanuts = 7 grams
Total protein from above sources = 65–70 grams
Other foods such as breads and cereals, pasta and rice, fruits, and other vegetables provide smaller amounts of protein, but provide lots of other nutrients as well.
We all need protein every day to meet our body's needs but moderation and variety is the key to an overall healthy lifestyle. For special dietary concerns, it is best to seek professional assistance.