The amino acid components of proteins are the building blocks of life itself. All activities of life require energy, which is derived from the calories in the food we eat. When protein and calorie intake are insufficient over a sustained period, the result is protein-energy malnutrition. A more common term for protein-energy malnutrition is starvation. Protein-energy malnutrition is considered to be a serious illness that is capable of inflicting multi-organ damage and is fatal if not corrected.
Protein Requirements
The average adult requires .8 grams of protein per kilogram of body weight, according to the Harvard School of Public Health and the Institute of Medicine. The average American has a diet that is 15 percent protein. The Harvard School of Public Health states that healthy adults can increase this to 20 percent or 25 percent, which can reduce the risk of heart disease if the increased protein replaces refined foods such as white bread, white rice and sugar. The school also recommends that people with diabetes and early kidney disease consume a protein amount that is 10 percent of their daily caloric intake.
Protein Quality
The body does not store protein the way it stores fat and carbohydrates, so all your protein requirements must be consumed on a daily basis. The Centers for Disease Control and Prevention states that protein quality is important. It recommends the selection of high quality or "complete" proteins, which means that dietary proteins must contain sufficient quantities of essential amino acids. If any of the essential amino acids are missing even for one day, then the body will break down muscle in order to get the amino acids needed. Humans can make only 10 of the 20 amino acids needed by the body. Essential amino acids cannot be made by the body, so they must be obtained from dietary sources. Essential amino acids are: arginine which is necessary for the young, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Animal sources of protein such as eggs, meat, poultry, fish, milk and cheese are considered to be complete. Most Americans have diets containing adequate amounts of protein.
Causes of Protein-Energy Malnutrition
According to the Merck Home Manual, protein-energy malnutrition is caused by lack of access to food; by illnesses or drugs that interfere with intake, metabolism or absorption of nutrients; or an exceptionally increased need for calories. Poverty, famine, wars and natural disasters create problems with food access. Lack of access occurs mostly in developing countries. In America, lack of access is found among the poor and elderly. Vomiting, diarrhea, kidney failure, diabetes, inflammatory bowel disease and AIDS are examples of illnesses that can interfere with absorption of nutrients. Anorexia nervosa, bulemia and the use of extremely low calorie diets are self-inflicted causes of protein-energy malnutrition.
Clinical Manifestations
Protein-energy malnutrition manifests clinically as fatigue, lightheadedness and progressive weight loss. This condition affects all organ systems because all cells contain protein and require energy to maintain normal metabolic functioning. Reduced heart size, low blood pressure, slow heart rate and heart failure are cardiovascular manifestations of starvation. Respiratory symptoms include slow breathing, reduced lung capacity and respiratory failure. Muscles are reduced in size and strength. With the blood there is anemia, low body temperature and edema. For the gastrointestinal system, there is decreased production of stomach acid, loss of stomach volume and diarrhea that can be fatal. The immune system becomes impaired. With the nervous system there is impaired concentration, mental dysfunction in the elderly and potential mental retardation in the young. The skin becomes dry and the hair becomes brittle and may fall out. Nails lose their strength and integrity. Review your diet with your health care provider to make sure you are getting enough complete protein and calories.
References
- Harvard School of Public Health; The Nutrition Source: Protein; 2011
- Centers for Disease Control and Prevention; Nutrition for Everyone: Protein; February 2011
- University of Arizona Department of Biochemistry; The Biology Project: The Chemistry of Amino Acids; September 2003
- Merck Home Manual; Undernutrition: Disorders of Nutrition and Metabolism; August 2007
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