Nutritional Assessment

A nutrition assessment is an in-depth evaluation of both objective and subjective data related to an individual's food and nutrient intake, lifestyle, and medical history.

Once the data on an individual is collected and organized, the practitioner can assess and evaluate the nutritional status of that person. The assessment leads to a plan of care, or intervention, designed to help the individual either maintain the assessed status or attain a healthier status.

Elements of the Assessment

The data for a nutritional assessment falls into four categories: anthropometric , biochemical , clinical, and dietary.

Anthropometrics.

Anthropometrics are the objective measurements of body muscle and fat . They are used to compare individuals, to compare growth in the young, and to assess weight loss or gain in the mature individual. Weight and height are the most frequently used anthropometric measurements, and skinfold measurements of several areas of the body are also taken.

As early as 1836, tables had been developed to compare weight and height in order to provide a reference for an individual's health status. The Metropolitan Life Insurance Company revised height and weight tables in 1942, using data from policyholders, to relate weight to disease and mortality. There has been much discussion about the relevance (and appropriateness) of using the individuals who buy life insurance as a basis for "ideal" height and weight. There are also a number of problems with using a table to determine whether an individual is at the right weight—or even what the "ideal

weight" means. Tables should therefore be used only as a guide, and other measurements should be included in the data collection and evaluation.

In 1959, research indicated that the lowest mortality rates were associated with below-average weight, and the phrase "desirable weight" replaced "ideal weight" in the title of the height and weight table.

To further characterize an individual's height and weight, tables also include body-frame size, which can be estimated in many ways. An easy way is to wrap the thumb and forefinger of the nondominant hand around the wrist of the dominant hand. If the thumb and forefinger meet, the frame is medium; if the fingers do not meet, the frame is large; and if they overlap, the frame is small.

Determining frame size is an attempt at attributing weight to specific body compartments. Frame size identifies an individual relative to the bone size, but does not differentiate muscle mass from body fat. Because it is the muscle mass that is metabolically active and the body fat that is associated with disease states, Body Mass Index (BMI) is used to estimate the body-fat mass. BMI is derived from an equation using weight and height.

To estimate body fat, skinfold measurements can be made using skin-fold calipers. Most frequently, tricep and subscapular (shoulder blade) skin-folds are measured. Measurements can then be compared to reference data—and to previous measurements of the individual, if available. Accurate measuring takes practice, and comparison measurements are most reliable if done by the same technician each time.

To estimate desirable body weight for amputees, and for paraplegics and quadriplegics, equations have been developed from cadaver studies, estimating desirable body weight, as well as calorie and protein needs. Calorie needs are determined by the height, weight, and age of an individual, which determine an estimate of daily needs.

The Harris-Benedict equation is frequently used, but there are quicker methods to estimate needs using just height and weight. Opinions and methods vary on how to estimate calorie needs for the obese . As previously mentioned, body fat is less metabolically active and requires fewer calories for support than muscle mass. If an individual's current body weight is more than 125 percent of the desirable weight for the individual's height and age, then using body weight to estimate calories needs usually leads to an over-estimation of those needs.

Biochemical data.

Laboratory tests based on blood and urine can be important indicators of nutritional status, but they are influenced by nonnutritional factors as well. Lab results can be altered by medications, hydration status, and disease states or other metabolic processes, such as stress . As with the other areas of nutrition assessment, biochemical data need to be viewed as a part of the whole.

Clinical data.

Clinical data provides information about the individual's medical history, including acute and chronic illness and diagnostic procedures, therapies, or treatments that may increase nutrient needs or induce malabsorption . Current medications need to be documented, and both prescription drugs and over-the-counter drugs, such as laxatives or analgesics, must be included in the analysis. Vitamins , minerals , and herbal preparations also need to be reviewed. Physical signs of malnutrition can be documented during the nutrition interview and are an important part of the assessment process.

Dietary data.

There are many ways to document dietary intake. The accuracy of the data is frequently challenged, however, since both questioning and observing can impact the actual intake. During a nutrition interview the practitioner may ask what the individual ate during the previous twenty-four hours, beginning with the last item eaten prior to the interview. Practitioners can train individuals on completing a food diary, and they can request that the record be kept for either three days or one week. Documentation should include portion sizes and how the food was prepared. Brand names or the restaurant where the food was eaten can assist in assessing the details of the intake. Estimating portion sizes is difficult, and requesting that every food be measured or weighed is time-consuming and can be impractical. Food models and photographs of foods are therefore used to assist in recalling the portion size of the food. In a metabolic study, where accuracy in the quantity of what was eaten is imperative, the researcher may ask the individual to prepare double portions of everything that is eaten—one portion to be eaten, one portion to be saved (under refrigeration, if needed) so the researcher can weigh or measure the quantity and document the method of preparation.

Food frequency questionnaires are used to gather information on how often a specific food, or category of food is eaten. The Food Guide Pyramid suggests portion sizes and the number of servings from each food group to be consumed on a daily basis, and can also be used as a reference to evaluate dietary intake.

During the nutrition interview, data collection will include questions about the individual's lifestyle—including the number of meals eaten daily, where they are eaten, and who prepared the meals. Information about allergies , food intolerances, and food avoidances, as well as caffeine and alcohol use, should be collected. Exercise frequency and occupation help to identify the need for increased calories. Asking about the economics of the individual or family, and about the use and type of kitchen equipment, can assist in the development of a plan of care. Dental and oral health also impact the nutritional assessment, as well as information about gastrointestinal health, such as problems with constipation , gas or diarrhea, vomiting, or frequent heartburn.

Evaluation

After data are collected, the practitioner uses past experience as well as reference standards to assimilate the information into an assessment that provides an understanding of the individual's nutritional status. The practitioner uses the anthropometric data to assess ideal and desirable weight, as well as skinfold measurements to determine body fat. Height, weight, and age are plugged into the Harris-Benedict equation to determine calorie and protein needs. Using the clinical, biochemical, and dietary data, influences on the nutritional status can be determined. A nutritional intervention, which usually includes dietary guidance and exercise recommendations, is then formulated and discussed with the individual.

see also Adolescent Nutrition; Adult Nutrition; Anthropometric Measurements; Body Mass Index; Dietary Assessment; Eating Habits; Food Guide Pyramid; Nutrition; Nutrition Education; Obesity.

Carole S. Mackey

Bibliography

Christie, Catherine, and Mitchell, Susan, eds. (2000). Handbook of Medical Nutrition Therapy: The Florida Diet Manual. Lighthouse Point, FL: Florida Dietetic Association.

Grant, Anne, and DeHoog, Susan (1999). Nutrition Assessment and Support, 5th edition. Seattle, WA: Grant and DeHoog.

Williams, Sue Rodwell (1997). Nutrition and Diet Therapy, 8th edition. St. Louis, MO: Mosby.

Winkler, Marion Feitelson, and Lysen, Lucinda (1993). Suggested Guidelines for Nutrition and Metabolic Management of Adult Patients Receiving Nutrition Support. Chicago, IL: American Dietetic Association.

DIETARY ASSESSMENT

DIETARY ASSESSMENT. Dietary assessment is the process of evaluating what people eat by using one or several intake indicators. It is the best approach for identifying nutrients that are likely to either be under-or overconsumed by the individual or groups of interest. It also can be used to identify food patterns and preferences.

Dietary Status versus Nutritional Status

Dietary status is related to but not necessarily reflective of nutritional status. Nutritional status is a more comprehensive term, referring to health status as it is affected by nutrition. It is measured not only by assessing dietary status, but also by anthropometric, biochemical, and clinical measures. Because dietary methods are less invasive, somewhat easier to obtain than other physiological measures, and do not require medical training, they often are used initially for assessing nutritional inadequacy or excess. Physiological measurements are then used to confirm and corroborate dietary intake evaluation and to arrive at definitive assessments of nutritional status.

Tools and Standards for Assessment

To assess dietary intake, food composition tables for translating foods consumed into nutrients, and a reference against which dietary intakes may be compared, are needed. These tools have been updated and refined periodically and appropriate ways for applying them to assessment tasks are steadily clarified.

Overcoming Imperfections in Assessing Dietary Intake

All dietary assessment methods are imperfect, regardless of how well they are designed. Their major shortcomings and measures for dealing with the imperfections are described briefly below.

Capture Actual Intakes

The various methods for assessing dietary intake are summarized in Table 1 and elsewhere in detail (Dwyer, 1999). All assessment methods fail to capture actual energy intakes precisely and probably intakes of nutrients as well. Some of the errors are inevitable because human beings tend to misreport their food intakes, but the method used also influences assessment outcomes.

Dietary intake is sometimes assessed by an objective observer rather than by the eaters themselves. For example, the intake of a hospitalized patient often is assessed from measured differences of the food served to a patient less any unconsumed amounts. Such objective methods have the advantage of being less subject to reporting biases than those that rely solely on recall. However, more objective methods are time-consuming, costly, cannot usually be employed to assess typical intake, and fail to record all intake. Moreover, they may not reflect what people really eat, since people may eat differently when they know that they are being observed. For these reasons, most commonly used dietary assessment methods rely on eaters' self-reported intakes.

Most methods such as twenty-four-hour recalls, food records, and diaries underreport actual energy intake by at least 20 percent. Underreporting errors are even higher (30 percent or more) in certain groups, such as the obese, women, and the elderly. However, they also vary among individuals in ways that are not always easily identified by demographic or other distinguishing characteristics. The causes of underreporting include forgetting, unconscious alterations in recalling foods eaten (for example, when the individual knows that he or she is being watched), attempts to please the questioner, and occasionally lack of cooperation by the subject. Non-random biases are difficult to deal with statistically.

Intakes obtained using semiquantitative food frequency questionnaires have other shortcomings. This method presents the respondent with a food list. These prompts may decrease forgetting, but insertions and "false memories" of foods consumed or of the consumption of socially desirable foods may be reported rather than true intakes. Semiquantitative food frequency questionnaires are too imprecise to estimate individual intakes quantitatively. Nutrient intakes from semiquantitative food frequency questionnaires usually are overestimated. They usually are adjusted statistically to obtain more accurate estimates of usual intakes. Measures of usual energy intakes for accurate groups specified by sex and age obtained by other methods or from estimates of energy outputs are used to adjust them. They are often derived by "food frequency" approaches and may be accurate enough to provide reasonable group estimates, although such measures are not sufficiently accurate for individuals. Also, precise quantification of absolute amounts (as opposed to levels of intake ranked into quartiles or quintiles) is not possible. The biases involved in food frequency questionnaires are complex, and statistical methods for obtaining valid estimates of intakes are unavailable.

Understandably, retrospective methods that rely on memory are subject to "forgetting bias." Prospective methods, which rely on reporting food intake immediately or shortly after eating, are more subject to alterations in intake due to the individual's awareness that his or her intake is being recorded. The extent to which social desirability and reporting biases intrude in the various methods is unknown, but is probably considerable.

Not all of the problems associated with misreporting can be overcome by the method of choice, but some can be minimized by selecting the appropriate tool for the task at hand.

Obtain Representative Intakes

Dietary assessments must be done frequently and randomly to reflect usual intake faithfully. This is an important shortcoming because only usual intake is

correlated with nutritional status. A representative sample of randomly chosen days that includes both weekdays and weekends is best for obtaining accurate twenty-four-hour recalls or records. Semiquantitative or other food frequency questionnaires also may assist in providing information on usual food intake patterns.

Obtain Total Intakes

Many foods and beverages are fortified with nutrients, and a substantial proportion of the population takes nutrient supplements on a regular basis. For some individuals, these nutrient sources contribute a substantial amount of vitamins and minerals. Nutrient intakes from all sources, including foods and beverages, fortified foods, and nutrient supplements must be included in all dietary assessments. If only food sources are queried, this fact should be noted.

Use Complete Food Composition Tables

Once food intakes are obtained, these must be translated into nutrients using food, beverage, and supplement composition tables. Accurate nutrient intakes can be obtained if up-to-date and complete food composition tables are available; that is, the composition of fortified foods, nutrient supplements, and beverages must be included and tables must be complete for all nutrients and other bioactive substances of interest.

Appropriate References

Estimated nutrient intakes must be compared with appropriate references; in the United States and Canada, these are the Dietary Reference Intakes, or DRIs. Their use in dietary assessments is the subject of a recent report (Dietary Reference Intakes, 2000).

Inadequacies, Excesses, and Imbalances May Coexist

In the past, dietary assessments focused on dietary inadequacies. Although these are still relevant, nutrient excesses and imbalances of nutrients also are of concern in most Western countries, and therefore also must be considered. Several of the DRIs are helpful in these respects. DRIs for macronutrients will be published in the near future.

Appropriate Interpretation of Assessment Results

The estimated average requirement, or EAR, is the nutrient intake estimated to meet the requirement of half the healthy individuals in a particular life stage or gender group. The recommended dietary allowance, or RDA, is the average daily dietary intake that suffices to meet the nutrient requirement of nearly all (97–98 percent) healthy individuals in a particular life stage and gender group. The adequate intake, or AI, is a recommended intake based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of healthy people whose intakes are assumed to be adequate. The AI is used when an RDA cannot be determined. When the AI's are not based on mean intakes of healthy populations, these values are likely to be less accurate. The tolerable upper intake level (UL) is the highest usual daily nutrient intake likely to pose no risk of adverse health effects to almost all individuals in the general population. As intakes increase above the UL, the risks of adverse effects also increase. The assessment of dietary adequacy is imprecise. A specific individual's actual requirement for a specific nutrient generally is never known. Second, often the number of days that intakes are measured are likely to be insufficient to overcome errors in measuring intake and normal day-to-day variation. Although dietary data alone are not sufficient to assess nutritional status, intakes of individuals can be compared to certain of the DRIs. A usual intake based on a large number of days that is at or above the RDA or AI has a low probability of inadequacy. An intake above the UL places an individual at risk of adverse effects from excessive nutrient intakes. When observed intakes are habitually below the EAR, increased intakes usually are needed because the probability of adequacy is 50 percent or less. Habitual intakes between the EAR and the RDA also probably need to be improved because the probability of adequacy is less than 97 to 98 percent. Quantitative estimates of risk of inadequacy are more difficult to obtain. However, they can be calculated using methods described in a recent report (Dietary Reference Intakes, 2000).

The DRIs also are used to assess the dietary intake of groups. These assessments determine the percentage of individuals whose intakes are estimated to be inadequate. The EAR is used to estimate the prevalence of inadequate intakes within a group. A mean usual group intake at or above the AI implies a low prevalence of inadequate intakes. The UL is used to estimate the percentage of the population at risk of adverse effects from excessive intakes consumed on a chronic basis. Thus, the RDA is not used to assess nutrient intakes of groups.

Conclusions

Dietary assessment is a necessary component of nutritional status assessment of individuals, and also is useful for other purposes. It can be done using a variety of methods, each of which has advantages and limitations. However, regardless of which method is chosen, it is important that certain criteria be met. Intake from all sources (food, fortified food, beverages, and nutrient supplements) must be included. Sufficient numbers of days to represent usual intakes must be obtained. Complete food and supplement composition tables must be employed. Appropriate reference standards and statistical procedures for assessing intakes must be used. Dietary assessment methods work best in combination with other methods for the assessment of nutritional status.

See also Dietary Guidelines; Nutrition.

BIBLIOGRAPHY

Dwyer, J. T. (1997). "Assessment of Dietary Intake." In Modern Nutrition in Health and Disease, edited by M. Shils, J. A. Olson, M. Shike and A. C. Ross, 8th ed., pp. 887–904. Baltimore: Williams and Wilkins, 1997.

Dwyer, J. T. "Dietary Assessment." In Modern Nutrition in Health and Disease, edited by M. Shils, J. A. Olson, M. Shike, and A. C. Ross, 9th ed., pp. 937–962. Baltimore: Williams and Wilkins, 1999.

Nusser, S., A. L. Carriquiry, K. W. Dodd, and W. A. Fuller. "A Semiparametric Transformation Approach to Estimating Usual Daily Intake Distributions." Journal of the American Statistical Association 91 (1996): 1440–1449.

Poehlman, E. T. "Energy Needs: Assessment and Requirements in Humans." In Modern Nutrition in Health and Disease, edited by M. Shils, J. A. Olson, M. Shike, and A. C. Ross, 9th ed., pp. 95–104. Philadelphia: Williams and Wilkins, 1999.

Subcommittee on Interpretation and Uses of Dietary Reference Intakes and Upper Reference Levels of Nuturients, Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes: Applications in Dietary Assessment. Washington, D.C.: National Academy Press, 2000.

Johanna Dwyer

Dietary Assessment

A dietary assessment is a comprehensive evaluation of a person's food intake. It is one of four parts of a nutrition assessment done in a clinical setting. These four parameters of assessment include: (1) an assessment of anthropometrics (weight, height, weight-to-height ratio, head circumference, body mass index , etc.); (2) dietary assessment, which includes a diet history or food frequency analysis; (3) a physical examination with a medical history; and (4) biochemical exams or blood/urine tests.

Reviewing a person's dietary data may suggest risk factors for chronic diseases and help to prevent them. Laboratory tests may uncover malnutrition and detect problems before any side effects appear, such as the tiredness and apathy associated with iron-deficiency anemia . The strengths of a simple blood test and food intake record are that these are easy to do and are affordable and appropriate for most people.

Problems with using diet histories can occur because a person's memory about what he or she ate earlier may not be accurate. It can also be time-consuming to collect food intake records. There are also problems with interpreting food intakes, laboratory values, and appropriate weights and heights.

A final area of concern related to dietary assessment is what to do with the information once it has been gathered. Providing nutrition education and counseling to people of different ages and from different backgrounds requires a great deal of skill and a good understanding of diet quality, normal eating, and normal physical and psychosocial development. It is important to treat people as individuals with unique needs and concerns. Dietitians are trained to do this, but many health care workers are not trained to measure diet quality, define dietary moderation, or provide counseling.

see also Nutritional Assessment.

Delores Truesdell

Internet Resources

American Heart Association. "Healthy Lifestyle: Diet and Nutrition." Available from <http://www.americanheart.org>

U.S. Department of Agriculture (2000). "Dietary Guidelines for Americans," 5th edition. Available from <http://www.usda.gov/cnpp>

U.S. Department of Agriculture, Food and Nutrition Information Center. "Dietary Assessment." Available from <http://www.nal.usda/fnic>