The use of objective data to determine an individual’s nutritional status. Dietitians and nutritionists collect data from clients in order to develop appropriate individualized plans that assure that nutritional goals will be met. Typically an in-depth nutrition assessment includes four components: anthropometric measurements, laboratory tests, physical exam, and clinical evaluation and diet analysis. Anthropomet-ric measurements provide basic data like height and weight. Commonly these measurements are used to calculate a BODY MASS INDEX (BMI), which is the weight in kg divided by height in meters. Body fat is often estimated from measurement of tricep skinfold thickness or midarm circumference. The major problem with interpreting anthropo-metric values is that there are no universally agreed upon standards for comparison. Additionally, human error can result in inconsistent measurements. Other means of assessing body fat and lean body mass such as measuring electrical conductivity of a region of the body (BIOELECTRIC IMPE-DENCE ANALYSIS) are common in clinics.
Chemical laboratory tests can aid in detecting marginal nutritional deficiencies. However, interpretation depends upon the clinician’s understanding of the many factors that may affect a given parameter. Typical markers include serum albumin, the most prevalent non-cellular protein in blood, which has been used to assess the adequacy of dietary protein. Serum transferrin, a blood protein that transports IRON, is affected by iron deficiency anemia, pregnancy, and by serum iron overload. Urinary creatinine, a waste product from MUSCLE, can help determine muscle protein stores, since the amount of creatinine excreted in the urine is proportional to a person’s muscle mass. However, cre-
atinine excretion decreases with age. Health of the immune system is compromised by nutrient deficiencies, and total lymphocytes (white cell) count is often used to assess the status of the immune system. Infections and steroid therapy can invalidate this as a nutrition parameter.
Physical Exam and Clinical Evaluation
Although clinicians can usually identify patients with moderate to severe malnutrition, they may be less experienced at identifying patients with mild nutritional depletion. A medical history evaluates health status and uncovers underlying health issues and factors that can affect nutrition, such as alcohol and drug use, chronic disease, disabilities, or use of medications. While some signs relate directly to nutritional deficiencies as noted above, further investigation may be needed to define the underlying cause. For example, a fatty stool may indicate pancreatic insufficiency or inadequate bile production, or impaired absorption as in celiac disease. Conditions such as shortness of breath, diarrhea, constipation, nausea, gingivitis, physical pain, poor-fitting dentures, and medications may interfere with food intake and digestion. Emotional stress can lead to anorexia or depression and dramatically affect nutrient consumption. Many lifestyle factors influence food intake, including income, family structures, eating habits, physical activity, accessibility to food, use of alcohol and drugs, and philosophical or religious beliefs.
Dietary history is an essential part of nutrition assessment. The simplest form is the 24-hour recall. An interview or a questionnaire is used to determine all foods eaten in the preceding 24 hours and to estimate the quantities by using plastic food models of typical serving sizes. Alternatively, food consumption frequency can be estimated using a food checklist (food frequency questionnaire), for weekly or monthly intake of 40 to 80 of the most frequently used foods. This is a descriptive, qualitative approach. In contrast, food records and diet diaries describe the individual’s current food intake, recorded daily in terms of common household measures. To involve the client in behavior modification, she or he may also be required to record eating patterns, including locations, times, events, and feelings associated with a given meal. For evaluation, intake data are translated into
nutrient intake. Food composition tables form the basis of detailed nutrient intake calculations, and extensive computer software is available to aid in dietary analysis. Food scoring systems can be based on identifying foods that are the main contributors to the elevation of blood cholesterol, that contribute saturated fat or that compose a major food group.
In the final analysis, dietary nutrient intake is compared to a standard for evaluation. Typically this is the RECOMMENDED DIETARY ALLOWANCE (RDA). Since the RDAs are derived for large populations, an individual’s calculated nutrient intake that is somewhat lower than the RDA need not indicate a deficiency. Nutrient intake values less than two-thirds of the RDA are best interpreted as placing the individual at risk for undernutrition.