The Power of Protein

Protein plays a vital role in building, maintaining and repairing lean body tissues: muscles, tendons, ligaments, circulatory system, brain, immune system, skin and other organs. In fact, every cell in the human body contains protein. Proteins are complex organic compounds that are composed of smaller “building blocks” called amino acids. When you consume foods that contain protein, your body breaks down the protein into its amino acids, and rebuilds them in specific sequences to form the structures it needs. Amino acids are classified into two groups: essential amino acids, which cannot be made by the body and must be supplied by food, and nonessential amino acids, which are made by the body from the essential amino acids or through normal breakdown of proteins.

We require protein in our diet to allow for tissue repair and growth. Inadequate protein consumption can cause impaired development, loss of muscle mass, decreased immunity, weakening of the heart and respiratory system, and death. In many parts of the world, protein malnutrition causes kwashiorkor – you’ve seen the haunting images of a young child afflicted with this condition, naked and emaciated, but for the characteristic swollen belly. For most of us living in developed countries, getting sufficient protein is easy, but just like with the fats and carbohydrates, not all protein is created equal. A protein that contains all the amino acids needed to build new proteins is called a complete protein. Complete proteins are found in animal foods such as meat, fish, poultry, eggs, milk, and milk products such as yogurt and cheese. Soybeans are the only plant source of protein considered to be a complete protein. In contrast, incomplete proteins lack one or more of the essential amino acids. Sources of incomplete protein include beans, peas, nuts, seeds, and grain. A small amount of incomplete protein is also found in vegetables. Plant proteins can be combined, however, to provide all of the essential amino acids and form a complete protein. Examples of combined, complete plant proteins are rice and beans, barley and corn, and lentil soup with potatoes.

We know that protein is critically important for growth and development during childhood, adolescence, and pregnancy, but there are other conditions associated with increased protein requirement including low calorie weight reduction diets and endurance and strength training. With regard to weight loss, recent studies have suggested that for most adults a high-protein, low carb diet may keep you leaner than a traditional high-carb, low-fat diet. This is partly because high protein foods slow the movement of food from the stomach to the intestine, delaying hunger. Also, protein’s moderate, steady effect on blood sugar and insulin levels avoids the quick, steep rise and fall that drives carbohydrate cravings after eating rapidly digested high glycemic foods. Finally, the body uses more energy to digest protein than it does to digest fat or carbohydrate. When a low calorie diet is used to accomplish a daily negative caloric intake, the goal is weight loss, meaning fat not muscle. This is why increasing protein in the diet is critical. If we do not receive adequate calories from food, the body will compensate by drawing on its own reserves, both its fat stores and lean body tissue. Ideal weight loss will occur only when there is a daily deficit of calories, coupled with adequate amounts of high quality protein that will allow for fat loss while preserving lean body mass.

Exercise, particularly weight training, can also lead to a daily protein requirement that exceeds the current recommended daily allowance of 0.8 grams per kg (about 0.4 gm/lb) body weight for a sedentary adult. Daily intake for the adolescent or adult athlete should be in the range of 1.0 – 2.0 gm/kg (0.5 – 1.0 gm/lb) body weight. Protein requirements of athletes and physically active adults are increased above those of sedentary people due in part to changes in amino acid metabolism induced by exercise. A small amount of protein is used as fuel during endurance exercise, and muscle and whole-body protein synthesis is suppressed during exercise. Increases in exercise intensity and duration further depress protein synthesis. Catch-up occurs after exercise when protein synthesis increases. Extra protein is then needed to repair injuries to muscle fibers and to remodel muscle tissue in response to endurance and strength training. Unless a protein-containing meal is consumed during recovery, breakdown will exceed rebuilding of muscle mass. Several studies indicate that protein synthesis during recovery is enhanced when the recovery meal contains both carbohydrate and protein. Whether you’re an elite athlete or simply an individual who’s looking to build body mass, lose body fat, and increase strength, proper protein consumption is essential.

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