It is not easy in spite of the mass of information accumulated in recent decades. Variation among individuals is great and the dividing line between normal and abnormal is not clear-cut. This might be anticipated since nutritional attributes and functions would be expected to show normal distribution curves as do other physiologic variables. Nor should this be discouraging, since similar difficulties are found in all fields of biological investigation and similar problems are en-countered in the diagnosis of cardiac, pulmonary or gastrointestinal disease. Basic scientific knowledge, coupled with astute clinical observation, forms the foundation of diagnostic acumen. Adeptness in the art of obtaining a medical history, keenness in detecting minor physical deviations from the normal, judicious choice of laboratory procedures, and ability to correlate all findings into a comprehensive whole, are the “sine qua non” for nutritional diagnosis as for diagnosis in other fields of medicine.
It is essential to know nutritional requirements and the function of nutrients in health and to be cognizant of the potential influence of disease on the requirement and utilization of nutrients. Knowledge of the effects of an inadequate supply of essential dietary factors is a requisite for accurate diagnosis. Cultivation of nutrition “consciousness” and an awareness of the nutritional aspects of biochemistry and metabolism is almost obligatory.
The medical history is of great importance in detecting the presence of disease which may. influence nutritional status and in eliciting symptoms which suggest nutritional abnormality. The physician should be aware of the physiologic, pathologic, or therapeutic situations which are prone to induce nutritional deficiency or excess.
Nutritive requirements may be increased in many diseases, particularly those in which basal metabolic rate is increased such as febrile illnesses, hyperthyroidism and certain other endocrinopathies, leukemia and polycythemia and diseases of the heart and lungs associated with severe dyspnea. In a number of psychotic states, abnormal physical activity increases total metabolic needs. Many diseases and some therapeutic agents interfere with ingestion, digestion or absorption of food. Diseases of the gastrointestinal tract and the myriad conditions associated with anorexia, nausea, vomiting and diarrhea belong in this category. Interference with the utilization of nutrients may be observed in hepatic disease, hypothyroidism, advanced renal disease, neoplasia, and following radiation therapy. Severe injuries, shock, and chronic anemic states profoundly affect metabolic processes. Nutrients may be lost from the body in conditions associated with polyuria, in therapeutic diuresis, and following ad-ministration of certain drugs.
Nutritional excess is best exemplified by an over-abundance of calories but metabolic disturbances and therapeutic agents may lead to syndromes in which excessive amounts of nutrients, particularly certain minerals and vitamins, accumulate in the tissues.
The physician must know the symptoms and signs associated with an inadequate or overabundant supply of each of the chemical substances essential in human nutrition.
These must be sought by adroit questioning and con-firmed or discarded by physical examination and appropriate laboratory procedures.
Findings in childhood which suggest nutritional deficiency include failure to grow or gain weight, poor appetite, lethargy, disinterest in play and irritability. In adults, some of the common complaints which may be associated with malnutrition are easy fatigability, loss of weight and strength and anorexia. Symptoms may indicate dysfunction of any of the bodily systems. Photophobia, burning of the eyes, lacrimation and night blindness may be observed. Soreness of the lips, tongue and angles of the mouth, digestive disturbances and diarrhea are not infrequent. Palpitation, dyspnea and edema may be due to nutritional deficiencies. Parasthesias and other sensory changes, particularly of the fingers and toes, easy bruising and dryness and pigmentary changes in the skin are often encountered. Since all of the above symptoms may occur in diverse pathologic conditions, all potential causative factors must be investigated.
The past medical record is valuable in indicating recent, recurrent or chronic disease or trauma, which may be related to the findings observed or affect nutritive state. Religious and social customs, occupation and economic status, in fact, practically all aspects of the environment whether geographical, physical or educational may exert an influence on food habits and on nutrition.
The family history, too, provides informative data. Family size, the record of illnesses and death, the occurrence of stillbirths, may shed light on nutritional problems. Fertility and the course of pregnancy are influenced by diet. Delayed puberty, amenorrhoea and impotence may be due to undernutrition or malnutrition as well as to other causes.
The dietary record is an important part of the medical history. Although a quantitative estimate of recent and habitual food intake may be difficult to obtain, it is usually possible to glean sufficient information to evaluate the diet from a qualitative standpoint. Several methods of obtaining dietary information have proved useful. A simple procedure is to ask the patient to recall the kinds and approximate amount of foods eaten in the previous 24 hours and to ascertain whether or not this is representative of the usual dietary pattern. The accuracy of the 24 hour diet record may be checked by the use of a list of common foods (divided into several principal groups), the patient being asked to indicate how often each is included in the diet (Table 1). Another method of obtaining dietary information is to have the patient keep a record of all food eaten, including amounts, for a period of several days to a week. These records are then evaluated by comparison with some dietary standard.
Difficulties in eliciting accurate dietary information are numerous. Many persons do not remember what they eat and have a poor idea of quantity; some tend to exaggerate, while others underestimate. Patients may be ashamed of the meagerness of their diets and conceal this information; others may describe their food intake in terms of what they believe the physician considers desirable. In spite of these and other pitfalls, the dietary record often suggests deficits which can be investigated further by clinical or laboratory tests.
Evaluation of the diet from a qualitative standpoint can be carried out easily by the physician in his office by using some simple standard such as that shown in Table 2. This was devised for appraisal of the diet of an adult in the United States. Similar tables can be prepared which are applicable to children or to other countries. If it is desirable to obtain more detailed information as to the quantity of specific nutrients in the diet, tables of food composition are available which permit such calculation (3).
Many dietary standards have been formulated by national and international groups (4) . The purpose of these standards and the philosophies on which they are based have varied widely. In the United States, the Recommended Dietary Allowances of the Food and Nutrition Board of the National Research Council have been used extensively (Table 3). These allowances represent the amounts of essential nutritive substances which appear desirable for the maintenance of good nutrition in essentially all healthy persons in the United States. They are more than minimum requirements and represent goals toward which to strive in planning diets and food sup-plies. If these allowances are used in quantitative evaluation of the diet of an individual, they must be interpreted correctly. A person whose diet meets recommended allowances will rarely exhibit nutritional deficiency, except in the presence of some disease which influences requirement or utilization of nutrients. On the other hand, if a person’s diet fails to fulfill recommended allowances, this does not necessarily signify nutritional deficiency. A nutrient intake considerably below recommended allowances suggests inadequate intake and requires additional investigation.
Dietary evaluation has been used extensively as one aspect of the appraisal of nutritional status of population groups. Dietary surveys are valuable particularly in areas where food supply is limited and have served as a basis for planning nutrition programs.
(1) The allowance levels are intended to cover individual variations among most normal persons as they live in the United States under usual environmental stresses. The recommended allowances can be attained with a variety of common foods. providing other nutrienta for which human requirements have been less well defined. See text for more detailed discussion of allowances and of nutrients not tabulated.
(2) Niacin equivalents include dietary sources of the preformed vitamin and the precursor, tryptophan. 60 milligrams tryptophan equals 1 milligram niacin.
(3) Calorie allowances apply to individuals usually engaged in moderate physical activity. For office workers or others in sedentary occupations they are excessive. Adjustments must be made for variations in body size, age, physical activity. and environmental temperature.
(4) See text for discussion of infant allowances. The Board reognizes that human milk is the natural food for infants and feels that breast feeding is the best and desired procedure for meeting nutrient requirements in the first months of life. No allowances are stated for the first month of life. Breast feeding is particularly indicated during the first month when infants show handicaps in homeostasis due to different rates of maturation of digestive, excretory and endocrine functions. Recommendations as listed pertain to nutrient intake as afforded by cow’s milk formulas and supplementary foods given the infant when breast feeding is terminated. Allowances are not given for protein during infancy survey method. Selection of proper standards with which to judge the nutritive value of diets is important; standards applicable in one community may require modification in another. Methods and procedures which may be useful in dietary surveys are discussed in several recent reviews.
A thorough and detailed physical examination can give much information relative to nutritional status although laboratory procedures may be needed to substantiate diagnosis. It should be kept in mind that nutritional deficiencies are often multiple and that similar lesions may be caused by an inadequate supply of more than one nutrient. Furthermore, the type of physical abnormality encountered varies according to the duration and severity of the deficiency. There are almost no pathognomonic findings, a situation which holds in other diagnostic fields. However, a combination of symptoms and signs, together with historical and laboratory data will permit accurate diagnosis in most instances.
General inspection yields much valuable information; in fact it is often possible to tentatively appraise the whole nutritional problem if observation is sufficiently keen. Observation begins when the patient is first seen in the home, office or hospital, and while the history is being recorded. The physician gains an impression of the patient’s general health, vigor, intelligence and emotional reactions. Gross defects in caloric nutrition are obvious; excessive fat pads denote obesity, absence of subcutaneous fat indicate excessive leanness; folds of sagging, inelastic skin suggest marked loss of weight. The stature, general skeletal development, bulk of muscle, color and texture of skin and hair are noted almost subconsciously. Edema of marked degree is readily detected. The general attitude and behavior of the patient, alertness or apathy, anxiety or depression, the facial expression, manner of speech and type of voluntary movements, all contribute to solution of the diagnostic problem. This is particularly true when severe malnutrition is suspected; in starvation and severe protein deficiency, depression, apathy and lassitude are characteristic findings. Differences in physiological and emotional reactions among various racial groups and among individuals must be considered in reaching an evaluation. Observation of the spontaneous behavior of children has been found to be most useful in appraising nutritional status. Lassitude, lack of interest and absence of spontaneous play are common in malnutrition. In children, too, posture may reflect nutriture: a forward slump of the head, kyphosis, lordosis, winged scapula and pot belly, all of which are expressions of poor muscle tone, are observed frequently among those who are poorly nourished.
Detailed physical examination of all systems of the body should follow general inspection. When nutritional diagnosis is applied to population* groups, especially in large or rapid nutrition surveys, attention is directed particularly to the superficial tissues, the skin, hair, mucocutaneous junctions, eyes, and buccal mucous membrane.
Schedules have been prepared for use in such nutritional appraisal. Some of the physical findings commonly associated with malnutrition which may be searched for in nutrition surveys are given in Table 4. These abnormal signs and symptoms are also useful in evaluating the nutritional status of the individual patient. It is obvious that many of these findings are non-specific and that some are more closely related to malnutrition than others. The presence of several abnormalities is more significant than a single deviation from normal. Interpretation is not easy and must be considered in con-junction with the dietary history and laboratory tests. Some of the findings which are suggestive of specific nutritional deficiency are given in Table 5 and will be discussed in detail in subsequent sections.
A number of laboratory procedures have been developed which are useful in evaluating nutritional status. While these will be considered subsequently in the discussion of each of the essential nutrients, a summary of normal values and of changes which may be observed in malnutrition is given in Table 6.
GROWTH OF INFANTS AND CHILDREN
In nutritional diagnosis in infants and children, appraisal of growth and development in relation to age and sex is of great importance. All types of nutritional deficiency may retard the rate of growth whether the deficiency represents an inadequate supply of calories, protein, vitamins or minerals. Growth rate is influenced, too, by disease and it is necessary to determine whether an in-adequate food intake, some pathologic process, or both, are responsible for retardation.
Assessment of growth implies a standard with which to compare the subject being examined. Unfortunately, present standards are far from precise and the optimal rate of growth remains unknown. The standards which have been developed by investigators at Iowa and Harvard Unversities (8) or the Wetzel grid are to be preferred to height-weight-age tables in evaluation of growth rate. Genetic and environmental factors must always be considered in the use of such standards. In any event, a single record of height and weight at a given age is of much less value than a long-term record, since the latter is indicative of rate of growth of the child in question. In a sense, the child becomes his own control and improvement or retrogression can be appreciated readily. The nutritional or other cause of change should then be determined. Another method of evaluating growth is estimation of skeletal maturation. Several procedures for this have been devised.
Many studies have indicated the important influence of nutrition on the course of pregnancy and on the condition of the infant at birth. The incidence of still-births and premature births and the birth weight of full term infants is affected by maternal nutritional state. Data relative to these findings have been collected in certain areas and used in partial evaluation of nutritional status of population groups.
Determination of height and weight of school children also gives information which has proved useful in nutrition surveys. The rate of growth of children is a sensitive index of food supply and dietary practices. Conclusions from such data will be valid only if satisfactory standards are available for the population group in question or if comparison can be made between several homogeneous sections of the population. Changes which occur following institution of programs designed to improve nutrition will also be informative.