Most people in the United States have little or no trouble meeting their need for protein. However, some individuals with lower standards of living, such as the elderly and certain ethnic groups, and others with higher protein needs, such as pregnant teenagers or women who are breast-feeding, may be deficient in this nutrient.
For them, the addition to the diet of low-cost, high-quality protein foods such as poultry or nonfat dry milk, or the substitution of yogurt, cheese, or milk for less nutritious snacks may make up for missing protein.
Serious protein deficiencies, found in environments of extreme deprivation, are usually protein-calorie deficiencies caused by a lack of all types of good food, not just protein. In order for people to exist on low levels of protein, their diets must supply sufficient energy (calories) from other sources – namely carbohydrates and fats. The symptoms of protein-calorie malnutrition include fatigue, lowered body resistance to infection, stunted growth, and mental retardation.