by National Council of Strength and Fitness
Protein is essential for building and maintaining muscle as well as repairing muscle tissue damage that occurs during training. It is needed for the production of red blood cells, hormones, and maintenance of tissue such as hair, fingernails and skin. Protein also plays a vital role in immune system function, and diets lacking this nutrient can be linked to certain physiological abnormalities.
Protein is composed of 20-23 amino acids. In basic chemistry, these are simply varied configurations of carbon, hydrogen, oxygen and nitrogen. Sometimes called "the basic building blocks," each amino acid has a particular role in biological function. In order to meet basic daily physiological requirements, the body can create many of these amino acids. If the body cannot produce the protein, however, it must be ingested from a food source. Amino acids that require dietary intake are called "essential."
There are eight essential amino acids for adults and nine for infants. The nutritional quality of dietary protein depends greatly on amino acid structure and essential amino acid concentration.
Protein's biological value is determined by the amount of protein absorbed and retained by the body tissues in relation to total amount consumed. Food sources will contain protein in one of two forms: complete and incomplete.
Complete protein contains all the essential amino acids, providing the body with a highly usable nutrient. An incomplete protein is deficient in one or more essential amino acids, leaving the body with a protein of lower biological value.
HOW MUCH PROTEIN DO YOU NEED?
The RDA for protein consumption is .8 grams per kilogram of body weight. This recommendation is based on sedentary requirements. Runners have a higher protein requirement to meet the high demands that exercise stress puts on the muscle tissue.
Generally, physical stressors are split into two categories, endurance stress and resistance stress. Between 1.3 and 1.6 grams of protein per kilogram of body weight seems to be ideal for persons engaging in resistance training, although intakes as high as 2.2 g/kg might be required if you're doing high volume resistance training. Endurance athletes need 1.1 to 1.4 grams of protein per kilogram of body weight, depending upon intensity and volume. Proteins are used as a fuel source ( <10%) in long, intense bouts of exercise.
In addition, certain types of branched-chained amino acids are used in the TCA cycle, leaving any other excess protein non-usable for general protein synthesis. Furthermore, the eccentric phase of an activity such as running creates a greater stress on working tissues and leads to an increased breakdown of the muscle fiber.
WHAT KIND OF PROTEIN IS BEST?
Protein comes in many forms, and the physically active person needs to be aware of the sources that have the highest biological value. Most animal products are excellent sources of high quality protein. However, these sources - although desirable -can also be high in saturated fat and cholesterol.
A commonly asked question is, "Can vegetarian athletes eat enough protein to satisfy their bodies' needs?" The key for vegetarians is food combination. Lacto-ovo vegetarians (people who eat dairy products) seem to have little difficulty in meeting their protein requirements. Vegans (no animal products), on the other hand, need to structure their diet carefully in order to receive all the essential amino acids. They must be willing to eat large amounts of plant-based foods. For the male athlete with a healthy appetite, this may pose no problem, but female athletes may find the sheer quantities required difficult.
You need to be wary of cutting back on one area of your diet in an attempt to reduce saturated fat and cholesterol. Although your intentions are good, you can actually create a deficiency in other vital nutrients. A perfect example of this is red meat. An excellent source of biologically high quality protein, red meat is also a great source of iron and zinc. By removing red meat entirely from your diet, you not only have to compensate for the protein source loss, but the iron and zinc as well.
On the other hand, when replacing foods that are high in carbohydrates with protein substitutes, you might lose vital micronutrients. Whole grains and vegetables provide us with the dietary fiber necessary to maintain normal digestive function as well as energy sources for activity.
Just as consuming too little protein can lead to health-related problems, excessive protein intakes could have a similar effect. Due to the complexity of the protein molecule, deamination (breakdown) of this nutrient is difficult.
Furthermore, persons who engage in high protein dieting are at greater risk of cellular dehydration. When protein replaces carbohydrates, the water which is usually attached to the glycogen molecule is lost. This accounts for loss in water weight - the primary explanation for quick weight loss during high-protein diets.
A relationship exists between protein intake and calcium excretion. There needs to be a minimum calcium intake when ingesting foods high in protein. When calcium is lost, bone mineral density can be compromised, leading to osteoporosis and weak bones.
There is little if any data to support the notion that diets high in protein lead to renal disease, but that heavy protein consumption may exacerbate an existing problem. Undeniably, excess protein takes a lasting toll on the kidneys over extended periods. If you consume higher amounts of protein, it should match the need of your body based on physical activity.
Remember, although the human body can utilize protein, fat and carbohydrate sources for energy, your body works best on the latter two. A healthy diet should consist of 55-60% carbohydrates in accordance with the RDA.
Dieting programs that focus on one nutrient in the long term may pose more hazards then benefits.
Look to qualified allied health professionals for more assistance in designing appropriate dietary strategies to best attain your goals. After all, variety is the spice of life.
The information in this column was provided by the National Council of Strength and Fitness. The NCSF is a national education and certification organization for Health Professionals. Dedicated to the competency and knowledge development of individuals in the fitness industry, the NCSF focuses on the practical skills necessary for professionals to safely and effectively elicit health and fitness from their respective clientele. If you are interested in becoming a Certified Personal Trainer, contact the NCSF at 800-772-NCSF, or visit National Council of Strength and Fitness.