Nutrition Connection: The Power of Protein

(reprinted from Dietary Manager, April 2009)

Protein, one of the macronutrients, has received a lot of press in recent years—especially for weight loss and athletic performance. The original word for protein, proteos, means “prime importance” or “taking the first place.” Yet, compared to fat, carbohydrate, and vitamins, relatively little is known about protein.

We know that inadequate protein in the diets of children results in stunted growth, minimal muscle mass, weak immune systems, bloated bellies, and weakened organ systems— a condition called kwashiorkor. If adequate protein is not provided, these children will probably not survive to adulthood.

In the United States and other developed countries, getting adequate dietary protein each day is fairly easy. Based on studies looking at minimal protein intake, the Institute of Medicine (IOM) recommends 0.8 gm/kg/day. This level of protein is sufficient to keep healthy adults from breaking down their own tissues. That is about 8 grams or 1.5 teaspoons of pure protein for every 20 pounds of body weight. Individuals with acute illnesses, severe infections, wounds, and following surgery have higher protein needs. Recent studies are proposing higher protein requirements for older adults.

Protein Basics

Protein is a part of all forms of plant and animal life. It is the major structural component of all cells in the body. Proteins function as enzymes, in membranes, as transport carriers, and as hormones. These chemical compounds are made up of carbon, hydrogen, and nitrogen. Some proteins contain sulfur atoms too.

Protein is composed of amino acids joined together by chains to form specific proteins. There are 21 amino acids. Nine of these amino acids must come from dietary sources every day. These amino acids are called indispensable or essential amino acids. The other 11 amino acids are called dispensable or nonessential because the body can synthesize them as long as there is enough nitrogen in the diet. Some of the dispensable amino acids are called conditionally indispensable because the body cannot make these fast enough during serious illness or injury.

Unlike fat, protein is not stored in the body for later use. Body components made of protein contribute about 24 pounds to the total weight of a 150-pound adult. About half of the body protein is in the form of skeletal muscle. The rest is part of vital organs, blood, enzymes, and hormones. Every molecule of body protein has an important job to do.

Protein Energy Connection

The amount of protein needed each day is estimated to be about 0.8 gm/kg actual body weight. This requirement assumes that the patient/resident is eating enough energy to maintain current body weight. Patients/residents who consume very low calorie diets have higher protein requirements than those who meet their energy needs. When individuals are consuming both a low calorie and low protein diet, some of the protein is converted to glucose and used for body fuel.

Protein Inequalities

Not all dietary protein is of the same nutritional value. Some of the protein you eat contains enough of all the indispensable amino acids needed to build new proteins, but not all of it. A protein that contains sufficient amounts of all of the indispensable amino acids is called a complete protein. Animal sources of protein, i.e. meat, eggs, milk, fish, poultry, etc., tend to be complete proteins. However, ground meats, especially those with moderate to high levels of fat or products that contain fillers, are often not complete proteins. Ground meats may contain all the indispensable amino acids, but the quantities are not sufficient to be complete proteins.

Grain products, fruits, vegetables, and nuts are incomplete sources of protein. These foods do not contain adequate amounts of all of the indispensable amino acids. Some foods are lacking one or more of the indispensable amino acids. Other foods contain all the indispensable amino acids, but the amount does not meet the requirements.

The Protein Shuffle

Protein nutrition involves both dietary protein and body protein reserves or lean body mass. Protein reserves are different from stores in that reserves need to be recycled each day to maintain a healthy body.

The daily turnover of protein in the body is several times the total dietary intake. The body requires about 340 gm of protein each day! About 90 gm of protein comes from dietary sources and the rest (about 250 gm) is recycled from lean body mass or protein reserves. Each day the body takes dietary protein and breaks it down into amino acids. Next, the body breaks down lean body reserves for the balance of the protein needed. When the diet is low in protein, more protein comes out of the lean body mass to maintain the body.

Both dietary protein and body protein reserves provide indispensable and dispensable amino acids. The body uses the amino acids to repair injuries, make hormones, and synthesize other vital body components. When protein needs are met, the body is able to recycle all of the protein reserves back to the original levels. During periods of growth or healing, the body needs to add to the protein reserves. However, when protein intake is low, the body recycles less lean body mass than it degraded.

The Poor Eater

What happens to the resident/patient who consumes very little protein each day? The cycle of protein turnover continues whether the individual consumes protein or not. When dietary protein is insufficient, the body breaks down more and more of the body protein reserves. Remember that the body must have a certain amount of each of the indispensable amino acids each day to build new protein. Extra amino acids are excreted in waste products. As time passes, the protein reserves are slowly depleted and the individual is at greater risk for infections, weight loss, skin breakdown, and death.

Protein Supplements

Commercially prepared protein supplements are one way to meet protein needs of the poor eater. There are dozens of products on the market, but just like food protein, these products are not nutritionally alike. Products made from whey isolate, whey concentrate, casein, or soy are almost always complete proteins. However, products made from collagen (animal skin) or collagen-whey or other combination products may or may not be complete products. Collagen is naturally devoid of an important indispensable amino acid—tryptophan. It is also low in all the other indispensable amino acids. Some collagen-based products are fortified to contain equivalent amounts of all the indispensable amino acids.

To determine if the protein supplement is a complete product, the Protein Digestibility Corrected Amino Acid Score (PDCAA S) is calculated. This score compares the quality of the protein supplement to the requirements. The highest score is 100 percent, meaning it contains sufficient amounts of all the indispensable amino acids. A score of less than 100 percent means that one or more of the indispensable amino acids is deficient. A score of zero means the product is lacking one or more of the indispensable amino acids. Some manufacturers advertise the PDCAAS on their point of sale materials. It is prudent to check their calculations to be sure the numbers add up. A registered dietitian can help you determine the PDCAAS.

Implications for Practice

All nutrition professionals involved in selecting/recommending supplemental products for patients/residents have a responsibility to know the nutritional value of the products. Remember that the reason why a protein supplement is ordered is to provide sufficient amounts of all the indispensable amino acids to repair injuries and fight infection. Be sure that the product you use provides the nutrition you think it provides. Giving poor quality or incomplete protein to a patient/resident with increased protein needs will not improve outcomes and may even be harmful to some individuals. Always taste test products to be sure the individual will accept them. Add other foods like ice cream or pureed fruit and flavorings to enhance the flavor. Avoid serving the same item repeatedly. Develop a cycle menu of different flavors or use different products to avoid taste fatigue.

Look for ways to incorporate protein supplements into foods. Remember that added protein in the diet means more work for the kidneys to process and excrete the wastes. Always monitor hydration status to be sure the patient/ resident has adequate fluid intake to manage the additional nitrogen in the diet.

By Mary D. Litchford, PhD, RD, LDN

Mary Litchford, PhD, RD, LDN is a nationally recognized speaker and author of Protein Powders, Potions & Elixirs.