Our Modern Diet - The Good / What are Proteins?

submitted by Dr. Gary Farr Last Updated February, 2, 2006

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The word "protein" is derived from the Greek language and means "of primary importance". What are proteins? We are protein. Our hair, our nails, our skin, our blood, our enzymes and hormones are protein; indeed, our bodies contain some ten thousand to fifty thousand kinds of protein. But these proteins are constantly being broken down into amino acids AMINO ACIDS, recycled and built anew, even oxidized to some extent to provide energy (1 gram of protein weighs in at 4 calories, the same as CARBOHYDRATE). In the typical American diet, about 20 percent of the day's total calories come from protein.

Just to sustain life, we need daily infusions of top-quality proteins because our bodies cannot store them (or their building blocks, the amino acids) the way they store FATS. The proteins we eat may be complete, meaning they contain all the amino acids we need and in the portions necessary to good health. Or they may be incomplete (lacking one or more essential amino acids). They are further categorized as simple proteins (containing nothing more than amino acids) or conjugated (amino acids bonded with nonprotein molecules). Collagen, a form of connective tissue, is a good example of a simple protein; hemoglobin, of a conjugated one (it's composed of amino acids plus a heme [IRON] group). It's important to know, too, that proteins can complement one another. That when a food lacking a specific essential amino acid is eaten with another food that supplies the missing amino acid, the result is a high-quality protein. Three examples of these complementary proteins: cooked dried beans eaten with rice, a peanut butter sandwich (i.e., bread plus peanut butter) and split pea soup accompanied by corn bread.

When a healthy adult (pregnant women excepted) receives and utilizes the amount of protein he or she needs, that person is said to be in nitrogen equilibrium. Pregnant women and growing children are in positive nitrogen balance, meaning their nitrogen intake exceeds that lost (they need it for growth, building of new tissue). On the other hand, those with illness or injury exhibit negative nitrogen balance because they excrete more nitrogen than they consume. As a general rule, the amount of good-quality protein needed to achieve nitrogen equilibrium is 0.8 grams per day per 2.2 pounds (1 kilogram) of body weight for adults. A dire shortfall of protein leads to marasmus, a severe form of protein-calorie malnutritin common among children in developing countries. What determines the quality, the biological value of protein? The amino-acid mix; specifically, the number, type and proportion. Egg whites, with a biological value of 100, contain the right amount of the right amino acids needed to meet the body's needs. Indeed, they are the standard against which other proteins are measured.

Good Sources of Complete Protein: Eggs, meat, fish, poultry, milk and other dairy products.

Good Sources of Incomplete Protein: Legumes (especially peas, beans, soybeans and peanuts), grains (especially unrefined), potatoes. Vegetarians, in particular, must choose their proteins carefully if they are to receive each day all the essential amino acids they need because plant proteins, in general, have a lower biological value than animal proteins. An incomplete protein may keep you alive, but it won't promote growth.

Q: What exactly is protein?
A: Proteins, like fats and carbohydrates, contain carbon, hydrogen, and oxygen. 1-3 However, proteins are unique because they also contain about 16%nitrogen,an essential element for all living beings. The basic structural unit of protein is the amino acid. Its fundamental use is as a building block for body proteins, such as enzymes, hormones, vitamins, and structural proteins. To form proteins, amino acids are combined into long chains by means of peptide linkages. 1,2 All of the necessary amino acids must be available in order to make a protein.

Q: Why is protein such an important part of my diet?
A: Protein is required for the growth, maintenance, and repair of all body tissues. 1-3 It is also required for the formation of enzymes and hormones that regulate body processes. Certain proteins transport oxygen, while others facilitate muscle contraction. As antibodies, they are involved in the function of the immune system. Protein can act as an energy source when needed in the fasting state or during extended physical exertion. Many vitamins and minerals are bound to specific protein carriers for transport. Protein is also necessary for blood clotting and fluid balance. In other words, proteins play a vital role in virtually every metabolic, structural, and physiologic process required for life!

Q: How much protein do I need every day?
A: There is a tremendous variance in daily protein requirements. Depending on several factors, proteins should account for anywhere from 10% to 40% of your daily caloric intake. These factors include your activity level, your lean body (muscle) mass, the type of protein you typically eat (vegetable or animal), your age, and your health status. A minimum daily protein requirement of 0.8 grams per 2.2 pounds body

Q: Do I get enough protein from my diet?
A: Many people, such as vegetarians, children, the elderly, those who exercise regularly, those who frequently diet, or those too busy to regularly eat a healthy diet, may find it difficult to consume adequate levels of high quality protein. For those who do have adequate protein in their diet, a great deal may come from high-fat sources such as red meat or cheese. Cutting back on these high-fat proteins and supplementing the diet with a high quality protein that is low in the less desirable fats would be a better choice.

Q: Is there anything that would increase my protein requirement?
A: There are many stresses to the body that can greatly increase your daily protein requirement, such as an infection or other illness, physical injury, or surgical trauma. 2 Even emotional stress can increase your protein requirement, which is compounded by the fact that when under stress we tend to make poor food choices. In addition, if you exercise a great deal, or are an athlete, you will likely need greater amounts of protein.

Q: What if I don 't get enough protein?
A:The body makes adjustments for low protein intake depending on the quality of the protein ingested and the level of energy intake. Beyond a critical point, however, the body can no longer adapt. Because protein is life sustaining, a dietary protein deficiency has a profound effect on the body; wasting of body tissues, fatty liver, diminished immune response, weakness, loss of vigor, and a host of other metabolic and physiologic consequences develop. Protein deficiency can also result in impaired growth in infants and children. With increasing age, lean muscle mass decreases and body fat mass increases. Women tend to be more protein deficient than men and therefore start to lose lean muscle mass earlier than men. This decline in skeletal muscle mass may contribute to age-related reductions in bone density, insulin sensitivity, and aerobic capacity. Thus increasing muscle mass and strength may be an important way to increase functional independence and decrease the prevalence of many age-associated chronic diseases.

Q: Who can benefit from a high quality protein supplement?
A: Individuals who have trouble meeting their protein needs can benefit from a high quality, convenient source of protein. They include children, the elderly, and athletes, as well as those who lead a busy lifestyle and find it difficult to eat a healthy, balanced diet. For those vegetarians that accept milk products (lactovegetarian), supplementing the diet with a high quality whey protein concentrate is an excellent way to ensure that protein needs are met. Also, because clinical factors can influence protein needs, those who can benefit from a high quality protein supplement include cancer patients (especially those undergoing chemotherapy), people with digestive diseases, anorexic patients, and pre-and post-operative patients.
 
Q: Are there differences between dietary proteins that are derived from different sources?
A: There is a big difference between proteins. This is because some types of protein supply all of the essential amino acids in ratios that "match" the needs of your body tissues. 1-3 These are called complete proteins . Other proteins supply a ratio of amino acids that differs from the average body protein or is missing one or more of the essential amino acids. These are called incomplete proteins. Another measure of protein quality is biologic value (BV), which reflects protein utilization in the body. The BV involves measurement of nitrogen intake from the dietary protein and nitrogen losses from the body,since nitrogen is unique to protein molecules. Thus, BV is the percentage of absorbed nitrogen retained and used by the body for growth or maintenance. Animal proteins such as eggs, milk, meat, and fish are complete proteins. However, there is a wide variance in the BV of these proteins. Vegetable proteins such as grains, beans, nuts, and seeds are incomplete proteins and thus have a lower BV (also due to their lower digestibility values). Therefore, more total protein is required in a vegetable protein diet than in a diet of mixed vegetable and animal proteins.

Q: What is whey protein?
A: Whey is a component of milk. The proteins of cow's milk are composed of approximately 80% casein and 20% whey protein. This is the reverse of human mother's milk, which is 70% to 80% whey protein. Whey itself has various constituents, including lactalbumin (the main protein in whey), lactoglobulin, lactoferrin, and immunoglobulins.

Q: What are the advantages of consuming a high quality whey protein concentrate?
A: A high quality whey protein concentrate is defined here as a product containing at least 80% protein with its naturally occurring constituents remaining largely undenatured and active, as verified by laboratory assay (both quantity and activity). This is accomplished through a special ultrafiltration/diafiltration, low heat, pH controlled process that offers significant advantages over traditionally processed whey protein powders. High quality whey protein concentrate has the highest biologic value (BV) of any protein, including egg, casein, milk, beef, or soy. It contains all essential and non-essential amino acids and is an excellent source of the branched-chain amino acids, which play a central role in muscular function. In addition, high quality whey protein concentrate as defined above contains very little fat and supplies other beneficial substances. These include bioactive immunoglobulins, enzymes, naturally occurring nutrients, and more. For providing both a basic dietary form of protein and for supplementation, A high quality whey protein concentrate is an excellent choice.

The Importance of Protein Proteins are fundamental to all forms of life. In humans ,they make up about three-quarters of the body solids and are used to build and repair every tissue in the body. Owing to their almost infinite number of possible structures, proteins play an incredibly diverse role in all facets of human physiology. These varying, indispensable roles illustrate the importance of consuming adequate levels of high quality protein.