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PART I: APPLYING THE DIETARY REFERENCE INTAKES 19 APPLYING THE DIETARY REFERENCE INTAKES T he goal of dietary assessment is to determine if the nutrient intakes of an individual or group are meeting the needs of that individual or group. The goal of dietary planning is to recommend a diet that provides ad- equate, but not excessive, levels of nutrients. It is important to note that when planning for individuals, the goal is to achieve recommended and adequate nutrient intakes using food-based guides. However, for group planning, this chapter presents a new approach, one based on considering the entire distribu- tion of usual nutrient intakes, rather than focusing on the mean intake of a group. While reading this chapter, keep in mind the following important points: First, the Dietary Reference Intakes (DRIs) apply to healthy people and do not pertain to those who are sick or malnourished or whose special circumstances may alter their nutrient needs. Second, an individual’s exact requirement for a specific nutrient is generally unknown. The DRIs are intended to help practition- ers arrive at a reasonable estimate of the nutrient level required to provide ad- equacy and prevent adverse effects of excess intake. Third, using the DRIs for assessment and planning is most effective when conducted as a cyclical activity that comprises assessment, planning, implementation, and reassessment. When assessing and planning diets, it is important to be mindful of the limitations in the data that underpin the DRIs and their application, which include the following: • The Estimated Average Requirements (EARs) may be based on data from a limited number of individuals. • For most nutrients, the precise variation in requirements is not known but is approximated. • In the absence of evidence to the contrary, variation in individual re- quirements is assumed to follow a normal distribution. • The EAR is often extrapolated from one population group to another. • The degree of uncertainty associated with the EAR has not been specified. The appropriate application of the DRIs represents a significant departure from

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 20 BOX 1 Definitions Associated with Assessing and Planning Nutrient Intakes Distribution of requirements: The distribution that reflects the individual- to-individual variability in requirements. Variability exists because not all individuals in a group have the same requirements for a nutrient, even if the individuals belong to the same life stage and gender group. Probability of inadequacy: The outcome of a calculation that compares an individual’s usual (long-term) intake to the distribution of requirements for people of the same life stage and gender group; used to determine the probability that the individual’s intake does not meet his or her requirement. Probability of adequacy: 100 percent minus the probability of inadequacy. Prevalence of inadequacy: The percentage of a group with intakes that fall below requirements. how nutrition assessment and planning were carried out using the former Rec- ommended Dietary Allowances (RDAs) and Recommended Nutrient Intakes (RNIs). Although many practitioners may have regarded the use of RDAs and RNIs as a way to determine “exact” assessments of intake, this presumed level of accuracy was actually misleading. Dietary assessment is not an exact sci- ence. In fact, it generally has always involved a process that included a “best estimate” of an individual or group’s intake. The new DRIs, however, afford an opportunity to substantially improve the accuracy of dietary assessment be- cause they allow practitioners to calculate the probability of inadequacy for an individual and the prevalence of inadequacy within a group and to plan for a low probability of inadequacy while minimizing potential risk of excess (see Box 1). These concepts are explained in greater detail later in this chapter, beginning with a short review of the statistical foundation underlying the con- cept of a distribution.

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 21 STATISTICAL FOUNDATION The DRIs and their applications are based on the statistical concept of a distri- bution. A distribution is an arrangement of data values showing their frequency of occurrence throughout the range of the various possible values. One of the most common distributions is a “normal” distribution, which is a symmetrical bell-shaped curve that has most of the values clustered in the center of the distribution and a few values falling out in the tails (see Figure 1). Important measures that describe a distribution are the mean, median, and standard deviation. • The mean is the average of the data values. It is calculated by adding all the data values and then dividing by the number of data values. • The median is the data value that occurs right in the middle of the distribution. It is the point at which half the data values are below and half the data values are above. The median is also referred to as the 50th percentile. In a symmetrical/normal distribution, the mean and median occur in the same place. • The standard deviation (SD) is a measure of how much, on average, each individual data value differs from the mean. The smaller the SD, the less each data value varies from the mean. The larger the spread of data values, the larger SD becomes. • The variance is another measure of how much individual data values differ from the mean. It is equivalent to the square of the standard de- viation (SD2). FIGURE 1 Schematic of a normal distribution.

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 22 EAR 50% 50% 34% 34% RDA 13.5% 13.5% 2.5% 2.5% –3 SD –2 SD –1 SD 0 +1 SD +2 SD +3 SD Mean Median Percentile Rank 2.5 16 50 84 97.5 FIGURE 2 Normal requirement distribution of hypothetical nutrient showing percentile rank and placement of EAR and RDA on the distribution. One important use of the normal distribution is the way it can be used to con- vert scores into percentile ranks, or probabilities. The “z-score” is a standard score that changes values into SD units (i.e., the score is now so many SDs above or below the mean). This score can be related directly to the normal distribution and the associated percentage probability of nutrient adequacy or inadequacy, as seen in Figure 2. By making use of this property of the normal distribution, the probability (or prevalence) of adequacy or inadequacy can be estimated. For example, a z- score of +1.50 is associated with a probability of adequacy of 93 percent. A z-score of –1.00 is associated with a probability of adequacy of 15 percent. Table 1 lists a selection of z-scores and their associated probabilities. It should be noted that not all data will form a normal distribution. For example, a “skewed” distribution is one where the curve has one tail longer than the other end. If the data do not form a normal distribution, then the properties of the normal distri- bution do not apply.

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 23 TABLE 1 Probability of Adequacy for Selected Z- Scores z-score Probability of Adequacy 2.00 0.98 1.65 0.95 1.50 0.93 1.25 0.90 1.00 0.85 0.86 0.80 0.68 0.75 0.50 0.70 0.00 0.50 –0.50 0.30 –0.85 0.20 –1.00 0.15 Applying the DRIs Makes Use of Two Distributions In applying the DRIs, two distributions are used simultaneously. The first is the distribution of requirements. The second is the distribution of intakes. REQUIREMENT DISTRIBUTION The distribution of requirements is the distribution upon which the DRIs (spe- cifically the EAR and RDA) are based. This distribution reflects the variability in requirements between individuals. Variability exists because not all individuals have the same requirement for a nutrient. For nutrients where requirements are normally distributed, the EAR is located at the mean/median of the distribu- tion. The RDA is located at 2 standard deviations above the mean, the level at which 97.5 percent of requirements should be met. INTAKE DISTRIBUTION The distribution of intakes is obtained from observed or reported nutrient in- takes gathered through dietary assessment methods such as 24-hour recalls. A 24-hour recall is a detailed description of all foods and beverages consumed in the previous 24-hour period. Nutrient intake from supplements should also be collected. When more than one 24-hour recall is collected, intake data can reflect the day-to-day variability within an individual that occurs because dif- ferent foods are eaten on different days.

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 24 When working with individuals, this variability is taken into account in the formulas used for assessment. When working with groups, statistical proce- dures should be used to adjust the distribution of observed intakes by partially removing the day-to-day variability in individual intakes so that the adjusted distribution more closely reflects a usual intake distribution. Usual intake is an important concept in application of the DRIs. Usual intake is the average intake over a long period of time. It is seldom possible to accurately measure long-term usual intake due to day-to-day variation in in- takes as well as measurement errors. Therefore, mean observed intakes (over at least two non-consecutive days or three consecutive days) are used to estimate usual intake. Overlap of the Requirement Distribution and the Intake Distribution The requirement and intake distributions can overlap to varying degrees. In some cases, the two distributions will barely intersect, if at all (see Figure 3, Panel A), and in others there may be a lot of overlap between intakes and re- quirements (see Figure 3, Panel B). In applying the DRIs to assessment, the distribution of intakes is compared to the distribution of requirements and inferences are made about the degree of adequacy. In dietary planning, efforts are made to ensure that the distribution of intakes is adequate relative to the distribution of requirements. WORKING WITH INDIVIDUALS How to Assess the Nutrient Intakes of an Individual The goal of assessing an individual’s nutrient intake is to determine if that in- take is meeting the person’s nutrient requirements. Assessment of dietary ad- equacy for an individual is difficult because of the imprecision involved in esti- mating an individual’s usual intake and the lack of knowledge of an individual’s actual nutrient requirements. Interpreting nutrient intake data in relation to the DRIs can enhance the assessment of an individual’s diet; however, the informa- tion obtained must be interpreted cautiously because an individual’s true usual intake and true requirements must be estimated, and assessment of dietary ad- equacy is only one component of a nutritional status assessment. Ideally, intake data are combined with clinical, biochemical, or anthropometric information to provide a valid assessment of nutritional status. Recognizing the inherent limitations and variability in dietary intakes and requirements is a major step forward in nutrition. The reports on using the DRIs for assessment and planning have provided a method with which one can

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 25 Panel A AI Median intake Theoretical requirement distribution Distribution of usual intakes 0 1 2 3 4 5 6 7 Nutrient X (mg/d) AI Median intake Panel B Theoretical Distribution of requirement usual intakes distribution 0 1 2 3 4 5 6 7 Nutrient X (mg/d) FIGURE 3 Overlap of requirement and intake distributions varies. estimate the degree of confidence that an individual’s intake meets his or her requirement. There are also equations that have been developed to estimate the degree of confidence that an individual’s intake is above the AI, and below the Tolerable Upper Intake Level (UL). It is important to keep in mind that the DRIs are estimates based on avail- able data, and that even when an EAR, RDA, and UL for a nutrient are provided for a life stage and gender group, there is considerable uncertainty about these values. Because information on both dietary intakes and requirements are esti- mated, it is very difficult to exactly determine whether an individual’s diet meets his or her individual requirement, even with the statistical approaches described

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 26 in this chapter. Thus, assessment of dietary intakes should be used as only one part of a nutritional assessment, and the results must be kept in context. Nutri- ent intake data should always be considered in combination with other infor- mation, such as anthropometric measurements, biochemical indices, diagnoses, clinical status, and other factors. Dietary adequacy should be assessed and diet plans formulated based on the totality of evidence, and not on dietary intake data alone. ESTIMATING AN INDIVIDUAL’S USUAL INTAKE AND REQUIREMENT To conduct a dietary assessment, information is needed on both dietary intakes and dietary requirements. Information on dietary intake of individuals is usu- ally gathered through food records or dietary recalls, and the requirement esti- mate is provided through the DRI process. In all cases the individual’s usual intake and true requirement can only be approximated. Estimation of Usual Intake Obtaining accurate information on dietary intakes is challenging for a num- ber of reasons, including the accuracy of dietary assessment techniques, as well as the challenges related to variability in intakes. The strongest methods for dietary assessment of nutrient adequacy are 24-hour recalls, diet records, or quantitative diet histories. Even so, the literature indicates that a sizeable pro- portion of individuals systematically misreport their dietary intakes, with the tendency toward underreporting (particularly for energy and percentage of en- ergy from fat). It is unclear how this affects the accuracy of self-reported intakes of nutrients. Well-accepted, validated methods to statistically correct for the effects of underreporting are presently lacking. There is also large day-to-day variation within a given individual’s intake due to factors such as variation in appetite, food choices, day of the week, and season. The result is that the calculation of dietary intake from one or even several days of intake may give an inaccurate estimate of that individual’s usual nutrient intake, especially if food choices vary greatly from one day to the next. Thus, observed dietary intake is probably not the same as the long-term usual intake of an individual. However, the observed mean intake is still the best available estimate of dietary intake, and can still be used providing that it is recognized there is an amount of variability associated with that best estimate. Estimation of Requirement It is nearly impossible to determine what an individual’s exact requirement for a nutrient is, unless that individual has participated in a requirement study.

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 27 Therefore, the fall-back assumption is that the individual’s requirement will be close to the average, in which case the EAR is the best estimate for an individual’s unobservable requirement. It is important to note that there is variation in nu- trient requirements between different individuals, and this needs to be taken into account when conducting an assessment. Using a Qualitative Approach to Assess an Individual’s Nutrient Intake Many users of the DRIs may find a qualitative assessment of an individual’s nutrient intakes to be useful. When conducting this type of descriptive assess- ment, it is important to keep in mind the limitations associated with the estima- tion of both intakes and requirements. For nutrients with an EAR and RDA: • Observed mean intake below the EAR very likely needs to be improved (because the probability of adequacy is 50 percent or less). • Observed mean intake between the EAR and the RDA probably needs to be improved (because the probability of adequacy is more than 50 percent but less than 97.5 percent). • Intakes below the RDA cannot be assumed to be inadequate because the RDA by definition exceeds the actual requirements of all but 2–3 per- cent of the population; many with intakes below the RDA may be meet- ing their individual requirements. • The likelihood of nutrient inadequacy increases as usual intake falls further below the RDA. • Only if intakes have been observed for a large number of days and are at or above the RDA should one have a high level of confidence that the intake is adequate. For nutrients with an Adequate Intake (AI): • If observed mean intake equals or exceeds the AI, it can be concluded that the diet is almost certainly adequate. • If, however, observed mean intake falls below the AI, no estimate can be made about the probability of nutrient inadequacy. • Professional judgment, based on additional types of information about the individual, should be exercised when interpreting intakes below the AI.

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 28 For nutrients with a UL: • Observed mean intake less than the UL is likely to be safe. • Observed mean intake equal to or greater than the UL may indicate a potential risk of adverse effects. The higher the intake in comparison to the UL, the greater the potential risk. For nutrients with an Acceptable Macronutrient Distribution Range (AMDR): • Observed mean intake between the lower and upper bound of the AMDR is within the acceptable range. • Observed mean intake below the lower bound or above the upper bound of the AMDR may heighten concern for possible adverse consequences. For energy: • Body mass index (BMI) should be used to assess the adequacy of energy intake, rather than a comparison to the Estimated Energy Requirement (EER). Using a Quantitative Approach to Assess an Individual’s Nutrient Intake An approach has been developed that statistically estimates the level of confi- dence that an individual’s usual intake is above an individual’s requirement, or below the UL. The equations developed for the assessment of individuals are based on the principles of hypothesis testing and levels of confidence based on a normal distribution curve. The equations proposed here are not applicable to all nutrients because they assume a normal distribution of daily intakes and requirements. For nutri- ents for which a distribution is skewed (such as iron requirements of menstru- ating women, or dietary intakes of vitamin A, vitamin B12, vitamin C, and vita- min E), a different methodology needs to be developed. For these nutrients, individual assessment should continue to place emphasis on other types of information available. NUTRIENTS WITH AN EAR For nutrients with an EAR, a z-score is calculated using the following equation: mean observed intake – EAR z - score = [(SD of requirement) +(within - person SD)2 / number of days of intake records] 2

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 29 The use of this equation requires the following information: • Mean observed intake: The mean nutrient intake of an individual is the best estimate of an individual’s usual intake. • EAR: The EAR is the best estimate of an individual’s requirement for a nutrient. • SD (standard deviation) of requirement: This is the variation in require- ments between individuals. It is calculated as the coefficient of variation (CV) times the EAR (see Appendix H). • Within-person SD of intake: The variation in day-to-day nutrient intake within the individual is an indicator of how much observed intake may deviate from usual intake. (This has been estimated in the original DRI reports by using CSFII data; see Appendix I.) • The number of days of intake records or recalls. As illustrated in Box 2, the equation solves for a z-score on the normal distribu- tion curve. Some z-scores and their associated probabilities are listed in Table 1. The larger the z-score, the larger the probability associated with that value. The numerator of the equation is the difference between the estimated intake and the estimated requirement. It can intuitively be seen that the higher an intake is compared to the requirement, the larger the numerator will be. The denomina- tor of the equation is the term that incorporates all the variability. Thus, as the variability gets smaller, the z-score will get larger. Note that an increase in the number of days of records will lead to a decrease in the amount of variability. NUTRIENTS WITH AN AI For nutrients with an AI it is not possible to estimate the requirement of indi- viduals. The AI represents an intake (not a requirement) that is likely to exceed the actual requirements of almost all individuals in a life stage and gender group. In fact, the AI may even be higher than an RDA (if it was possible to calculate one). When trying to compare an individual’s intake to his or her requirement, the AI is not very useful because it is in excess of the median requirement, perhaps by a very large margin. Therefore, when intakes are compared to the AI, all that can be concluded is whether the intake is above the AI or not. It is possible to determine the confidence with which one can conclude that usual intake exceeds the AI using the following equation:

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 58 TABLE 5 Using the Probability Approach to Estimate Group Prevalence of Inadequacy in a Group of 650 Adult Men Ages 19 to 30 Years for a Nutrient with an EAR of 7 mg/day Probability ¥ Usual Intake Level Probability of Number of Numbera (mg/day) Inadequacy People 2 1.0 10 10 3 1.0 10 10 4 0.97 20 19.4 5 0.90 20 18.0 6 0.73 30 21.9 7 0.50 50 25.0 8 0.27 60 16.2 9 0.10 80 8.0 10 0.03 100 3.0 11 0 100 0 12 0 80 0 13 0 60 0 14 0 30 0 Total 650 131.5 = probability ¥ number/total Average probability = 131.5/650 = 0.20 (20 percent) a This represents the number of men expected to have inadequate intakes at each intake level. Case Study Two: Using the Probability Approach to Assess Iron Intakes in a Group of Menstruating Women The probability approach involves first determining the risk of inadequacy for each individual in the population, and then averaging the individual probabili- ties across the group. For iron, Appendix Tables G-5, G-6, and G-7 give the probability of inadequacy at various intakes. These tables may be used to calcu- late the risk of inadequacy for each individual, and then the estimated preva- lence of inadequacy for a population. In addition, Appendix C of the original report titled, Dietary Reference Intakes: Applications in Dietary Assessment (2000), demonstrates how to carry out the necessary calculations to obtain a prevalence estimate for a group. This case study presents a simplified estimate that could also be deter- mined manually. The estimate is illustrated in Table 6 for a hypothetical group of 1,000 menstruating women not taking oral contraceptives and consuming a

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 59 typical omnivorous diet. The first and second columns of this table are based on information in Appendix Tables G-4 and G-7. Intakes below 4.42 mg/day are assumed to have a 100 percent probability of inadequacy (risk = 1.0). Indi- viduals with intakes above 18.23 mg/day are assumed to have a zero risk of inadequacy. For intakes between these two extremes, the risk of inadequacy is calculated as 100 minus the midpoint of the percentile of requirement. For example, intakes between 4.42 and 4.88 fall between the 2.5 and 5th percentile of requirement. The midpoint is 3.75, and the probability of inadequacy is 100 – 3.75 ª 96.3 percent, or a risk of 0.96. The appropriate risk of inadequacy is then multiplied by the number of women with intakes in that range. In this case study, only one woman had an intake between 4.42 and 4.87 mg/day, so the number of women with inadequate intake is 0.96 (1 ¥ 0.96). In the next range (4.88 mg/day to 5.46 mg/day, or between the 5th and 10th percentiles) there were three women, with an associated number of women with inadequate intake of 2.79 (3 ¥ 0.93). If this is done for each intake range, the total number of women with inadequate intakes can be determined. In this example, 165 of the 1,000 women have inadequate intakes, for an estimated prevalence of inad- TABLE 6 Illustration of the Full Probability Approach to Estimate the Prevalence of Dietary Iron Inadequacy in a Group of 1,000 Menstruating Women (Not Using Oral Contraceptives and Following an Omnivorous Diet) Range of Usual Percentiles of Intake Associated Probability Number of Number of Requirement with Requirement of Women with Women with Distribution Percentiles (mg/day) Inadequacy Intake in Range Inadequate Intake < 2.5 < 4.42 1.0 1 1 2.5–5.0 4.42–4.88 0.96 1 0.96 5–10 4.89–5.45 0.93 3 2.79 10–20 5.46–6.22 0.85 10 8.5 20–30 6.23–6.87 0.75 15 11.25 30–40 6.88–7.46 0.65 20 13 40–50 7.47–8.07 0.55 23 12.65 50–60 8.08–8.76 0.45 27 12.15 60–70 8.77–9.63 0.35 50 17.5 70–80 9.64–10.82 0.25 150 37.5 80–90 10.83–13.05 0.15 200 30.0 90–95 13.06–15.49 0.08 175 14 95–97.5 15.50–18.23 0.04 125 5 > 97.5 > 18.23 0.0 200 0 Total 1,000 165

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 60 equacy of 16.5 percent. It is important to remember that this approach does not identify the specific women with inadequate intakes, but is rather a statistical calculation of the prevalence of inadequate intakes. Thus, it cannot be used to screen individuals at risk of inadequacy. Note that the prevalence of nutrient inadequacy that is estimated by the full probability approach differs considerably from that estimated by the cut- point method (the proportion with intakes below the EAR). In this example, the EAR (median requirement) is 8.07 mg/day, and only 73 women have in- takes below this amount. Thus, the cut-point method would lead to an esti- mated prevalence of inadequacy of 7.3 percent, which differs considerably from the estimate of 16.5 percent obtained by using the full probability approach. The reason for the discrepancy is that one of the conditions needed for the cut- point approach (a symmetrical requirement distribution) is not true for iron requirements of menstruating women. Case Study Three: Using the EAR Cut-Point Method The EAR cut-point method is illustrated in Figure 10, which shows a hypo- thetical joint distribution of usual intakes and individual requirements for a group of 60 individuals. This example is hypothetical because in practice we almost never have access to accurate data on either usual intakes of individuals or their individual requirements. Figure 10 includes a 45∞ dashed line labeled “Intake = Requirement.” Individuals who fall to the right of and below this line have usual intakes that exceed their individual requirements (i.e., they have adequate intakes), whereas individuals who fall to the left of and above the line have usual intakes that do not meet their requirements (i.e., they have inad- equate intakes). Determining the prevalence of inadequacy in this hypothetical situation is easy: one simply counts the number of individuals with usual in- takes below their individual requirements. In this example, 13 individuals have intakes to the left of and above the “Intake = Requirement” line, so the group prevalence of inadequacy is 13/60, or 21.7 percent. Figure 10 also shows the EAR (in this example, it is 4 mg/day) on both the requirement axis (the Y axis) and the usual intake axis (X axis). Focusing on the X axis, note that most individuals with usual intakes below the EAR have inad- equate intakes (they are to the left of and above the “Intake = Requirement” line), but that some (who appear in the triangle labeled 1) have usual intakes that exceed their individual requirements. Similarly, although most individuals with usual intakes above the EAR meet their requirements (they are to the right of and below the “Intake = Requirement” line), some (who appear in the tri- angle labeled 2) do not.

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 61 8 EAR Intake = Requirement 2 7 Intake < Requirement 6 Requirement (mg/d) 5 EAR 4 3 2 Intake > Requirement 1 1 0 0 2 4 6 8 10 12 Usual Intake (mg/d) FIGURE 10 Joint distribution of requirements and usual intakes. Individuals with usual intakes below their individual requirements are found to the left of and above the dashed 45o line labeled Intake = Requirement. When assumptions for the EAR cut-point method are satisfied, this proportion of the group is mathematically similar to the proportion to the left of the vertical EAR line. The assumptions required for use of the EAR cut-point method are satis- fied in this example, as described below: 1. Requirement distribution is approximately symmetrical. In Figure 10, it can be seen that similar proportions of the group have requirements above and below the EAR of 4 mg/day (the number of individuals above the horizontal EAR line is similar to the number of individuals below). 2. Intakes and requirements are independent. Figure 10 shows that indi- viduals with low requirements are just as likely as individuals with high requirements to have high (or low) usual intakes. 3. The usual intake distribution is more variable than the requirement dis- tribution. In Figure 10, it can be seen that there is more variability in the intake distribution (it ranges from less than 2 mg/day to almost 10 mg/ day) than in the requirement distribution (which ranges from about 2 mg/day to about 6 mg/day).

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 62 When the above conditions are met, the individuals in triangle 1 (with intakes below the EAR but above their own requirements) are similar in number to the individuals in triangle 2 (with intakes above the EAR and below their own requirements). These two triangles cancel one another out, and the number of individuals that do not meet their requirements (those found to the left of the 45o “Intake = Requirement” line) is thus mathematically similar to the number with usual intakes below the EAR. The EAR cut-point method can also be applied to the example of 650 men described in the first case study, as the requirement distribution is symmetrical, intakes and requirements are independent, and the usual intake distribution is more variable than the requirement distribution. In this case, one would simply determine the number of men with intakes at or below the EAR of 7 mg/day. From Table 5, this would be 10 (2 mg/day) + 10 (3 mg/day) + 20 (4 mg/day) + 20 (5 mg/day) + 30 (6 mg/day) + 50 (7 mg/day), for a total of 140 men. Divid- ing this by the total group size of 650 yields the estimated prevalence of inad- equacy of 21.5 percent, which is very similar to the estimate of 20 percent obtained using the full probability method. In summary, the full probability method and a shortcut, known as the EAR cut-point method, can be used to estimate the prevalence of nutrient inad- equacy in a group. Both methods require knowledge of the distribution of usual intakes for the group, and that intakes and requirements are independent. The EAR cut-point method has two additional requirements; namely, that the re- quirement distribution is symmetrical, and that the distribution of usual in- takes is more variable than the distribution of requirements. If either of these two additional requirements is not met, the full probability method can be used instead, provided the requirement distribution is known. Case Study Four: Planning Diets in an Assisted-Living Facility for Senior Citizens An example of planning diets for institutionalized groups is menu planning for senior citizens who reside in an assisted-living facility. Menus planned for these institutions usually assume that the residents have no other sources of foods or nutrients, and thus the menus are designed to meet all nutrient needs of the residents. The goal of menu planning is to provide meals that provide adequate nutrients for a high proportion of the residents, or conversely, the prevalence of inadequate intakes is acceptably low among the residents. The planner is developing a menu for an assisted living facility in which the residents are retired nuns aged 70 years and above. For this age group, the EAR for vitamin B6 is 1.3 mg/day. Assume that no data can be located on the distribution of usual intakes of this group or a similar group, and that resources are not available to conduct a dietary survey in the institution. How could the

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 63 planner proceed to determine the target intake distribution of vitamin B6 needed to attain an acceptable prevalence of inadequacy? STEP 1. DETERMINE AN ACCEPTABLY LOW PREVALENCE OF INADEQUACY For vitamin B6, the EAR was set at a level adequate to maintain plasma pyri- doxal phosphate levels at 20 nmol/L. This plasma level is not accompanied by observable health risks, and thus allows a moderate safety margin to protect against the development of signs or symptoms of deficiency. This cut-off level was selected recognizing that its use may overestimate the B6 requirement for health maintenance of more than half the group. For this reason, assume that the planner has determined that a 10 percent prevalence of inadequacy (i.e., 10 percent with intakes below the EAR) would be an acceptable planning goal. STEP 2. DETERMINE THE TARGET USUAL NUTRIENT INTAKE DISTRIBUTION Next, the planner needs to position the intake distribution so the nutrient in- take goals are met. In this example, the planner decides that the prevalence of inadequacy in the group will be set at 10 percent, and as a result the usual intake distribution of the group should be positioned such that only 10 percent of the group has usual intakes less than the EAR. Because data on the usual nutrient intake distributions of the residents are not available, other sources must be used to estimate the target usual nutrient intake distribution. Data on the distribution of usual dietary intakes of vitamin B6 are available from several national surveys and thus are used. The adjusted percentiles for women are summarized in Table 7. Assuming there are no changes in the shape of the distribution, the amount of the shift can be calculated as the additional amount of the nutrient that must be consumed to reduce the proportion of the group that is below the EAR. This is accomplished by determining the difference between the EAR and the intake at the acceptable prevalence of inadequacy (in this case, the 10th percentile of the usual intake distribution). TABLE 7 Selected Percentiles of the Distributions of Usual Intake of Vitamin B 6 from Foods in Older Women Percentile of Usual Intake Distribution of Vitamin B6 (mg/day) Study n 5th 10th 25th 50th 75th 90th 95th Survey A 1,368 0.92 1.04 1.24 1.53 1.93 2.43 2.76 Survey B 221 0.76 0.88 1.11 1.41 1.76 2.12 2.35 Survey C 281 0.5 0.6 0.7 1.0 1.3 1.6 1.8

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 64 TABLE 8 Identification of the Target Median Intakea of Vitamin B 6 to Obtain a 10 Percent Prevalence of Inadequacy in Older Women Intake Difference Target at 10th (EAR – intake Median Median EAR Percentile at 10th Intake Intake Study (mg/day) (mg/day) percentile) (mg/day) (mg/day) Survey A 1.3 1.04 0.26 1.53 1.79 Survey B 1.3 0.88 0.42 1.41 1.83 Survey C 1.3 0.6 0.7 1.0 1.70 a The target median intake is estimated by adding the difference between the Estimated Average Requirement (EAR) and the intake at the acceptable prevalence of inadequacy (in this case, 10 percent) to the observed median intake. Examination of the data from the three surveys shows that estimated usual intakes of vitamin B6 vary by as much as 30 percent among the surveys. As a result, the difference between the EAR of 1.3 mg and the intake at the 10th percentile varies, depending on which data are used. Table 8 shows that for Survey A the difference is 0.26 mg (1.3 mg – 1.04 mg = 0.26 mg); for Survey B, the difference is 0.42 mg (1.3 mg – 0.88 mg = 0.42 mg); and for Survey C, the difference is 0.7 mg (1.3 mg – 0.6 mg = 0.7 mg). In this example, the planner may have no reason to choose data from one particular survey as “more appli- cable” to the group than another, so he may estimate target usual nutrient in- take distributions using all three data sets. Accordingly, the target intake distri- butions shift up by 0.26 mg, by 0.42 mg, and by 0.7 mg. using Survey A, B, or C. In each case the target usual nutrient intake distribution would lead to the accepted prevalence of inadequacy. Rather than choosing one set of survey data over another, the planner could simply average the summary measures described in the next section. STEP 3. SELECT A SUMMARY MEASURE OF THE TARGET USUAL NUTRIENT INTAKE DISTRIBUTION TO USE IN PLANNING After the planner has estimated a target usual intake distribution, then this information needs to be operationalized into a menu. In order to do this, the planner will first have to select a summary measure of the target usual nutrient intake distribution to use as a tool in planning the menu. The median of the target intake distribution is the most useful; it can be calculated as the median of the current intake distribution, plus (or minus) the amount that the distribu- tion needs to shift to make it the target usual intake distribution. In the current example, although the baseline intakes at the 10th percen- tile and the median differ among the three surveys, the estimates of the medians

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 65 of the target usual intake distributions are quite similar, as shown in Table 8. Assuming that a 10 percent prevalence of intakes below the EAR was consid- ered acceptable, a median intake for vitamin B6 of 1.7 to 1.8 mg/day would be the planning goal. Accordingly, the menu would need to be planned so that vitamin B6 intakes would be at this level. Estimates of target nutrient intakes must be converted to estimates of foods to purchase, offer, and serve that will result in the usual intake distributions meeting the intake goals. This is not an easy task. Meals with an average nutri- ent content equal to the median of the target usual nutrient intake distribution may not meet the planning goals, as individuals in a group tend to consume less than what is offered and served to them. Thus, the planner might aim for a menu that offers a choice of meals with a nutrient content range that includes, or even exceeds, the median of the target usual nutrient intake distribution. STEP 4. ASSESS IMPLEMENTATION OF THE PLAN Ideally, after the menu had been planned and implemented, a survey would be conducted to assess intakes and determine whether the planning goal had been attained. This would then be used as the basis for further planning. KEY POINTS FOR WORKING WITH GROUPS ASSESSING NUTRIENT INTAKES The goal of assessing nutrient intakes of groups is to determine 3 the prevalence of inadequate (or excessive) nutrient intakes within a particular group of individuals. Assessment of groups should always be performed using 3 intakes that have been adjusted to represent a usual intake distribution. The probability approach and the EAR cut-point method are 3 two statistical methods of determining the prevalence of inadequacy in a group. The EAR cut-point method is a simpler method derived from the probability approach. For nutrients in which it is appropriate to do so, the EAR can be 3 used as part of the EAR cut-point method to determine the prevalence of nutrient inadequacy within a group. Otherwise, the probability approach can be used. The AI has limited application in assessing a group’s nutrient 3 intakes. For nutrients with an appropriately estimated AI, groups with mean or median intakes at or above the AI can generally be assumed to have a low prevalence of inadequate intakes.

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 66 The UL can be used to estimate the proportion of a group at 3 potential risk of adverse effects from excessive nutrient intakes. The RDA should not be used in the assessment of a group’s 3 nutrient intakes. Comparing mean or median intake with the RDA is inappropriate. To assess the energy adequacy of an individual or group diet, 3 information other than self-reported intakes should be used because underreporting of energy intake is a serious and pervasive problem. Body weight for height, BMI, or other anthropometric measures are suitable for use in assessing long-term energy intake. PLANNING NUTRIENT INTAKES The goal of planning nutrient intakes for groups is to achieve 3 usual intakes that meet the requirements of most individuals, but that are not excessive. The DRIs present an approach to planning that involves 3 consideration of the entire distribution of usual nutrient intakes within a group. The basic steps in planning for groups are as follows: First the 3 practitioner decides on an acceptable prevalence of inadequacy. The distribution of usual intakes in the group must then be estimated using the distribution of reported or observed intakes. Finally, a target usual intake distribution is determined by positioning the distribution of usual intakes relative to the EAR to achieve the desired prevalence of inadequacy. For nutrients with an EAR, the planning goal is to aim for an 3 acceptably low prevalence of intakes below the EAR. The RDA is not recommended for use when planning nutrient 3 intakes of groups. For nutrients with an AI, this value is used as the target for the 3 mean or median intake when planning for groups. For nutrients with a UL, the planning goal is to achieve an 3 acceptably low prevalence of intakes above the UL. When planning a group’s energy intake, the goal is for the 3 group’s mean intake to equal the EER.

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PART I: APPLYING THE DIETARY REFERENCE INTAKES 67 SUMMARY The DRI values can be used by nutrition professionals to assess and plan the nutrient intakes of individuals and of groups. Table 9 summarizes the chapter discussions on the appropriate uses of each of the DRI values to achieve these goals.

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DRIs: THE ESSENTIAL GUIDE TO NUTRIENT REQUIREMENTS 68 TABLE 9 Using the DRIs to Assess and Plan the Nutrient Intakes of Individuals and Groups EAR RDA AI UL When Assessing Diets For individuals: Usual intake Not recommended Usual intake at Usual intake above below the EAR for use when or above the AI the UL may place an likely needs to assessing nutrient has a low individual at risk of be improved. The intakes of probability of adverse effects. probability of individuals. inadequacy. adequacy is 50 percent or less. For groups: Used as part of Not used when Limited Used to estimate the the EAR cut-point assessing nutrient application. proportion of a group method to intakes of groups. Groups with mean at potential risk of determine the or median intakes adverse effects from prevalence of at or above the excessive nutrient nutrient AI can generally intake. inadequacy within be assumed to a group. have a low prevalence of inadequate intakes. When Planning Diets For individuals: Intake at EAR Low probability of Intakes at AI will Low probability of has 50 percent inadequate intake likely meet or adverse effects from probability of not at RDA. Therefore, exceed an excessive meeting often used as a individual’s consumption so requirement. guide. requirement. average intake should not exceed the UL. For groups: Aim for an Not used when Use as a target Aim for an acceptably low planning the for the mean or acceptably low prevalence of nutrient intakes median intake. prevalence of intakes intakes below of groups. above the UL. the EAR.