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Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
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3

Defining the DRI Population

Since the first edition of the Recommended Dietary Allowances (RDAs) were published in 1941 (NRC, 1941), RDA committees have provided context to the intended populations for their recommendations, often referred to as “healthy populations” or “apparently healthy populations.” This definition was also used for dietary recommendations from the Canadian Council on Nutrition (Canadian Council on Nutrition, 1949). More recently, the joint U.S. and Canadian Dietary Reference Intakes (DRIs), the European Food Safety Authority (EFSA, 2022), and the Nordic Nutrition Recommendations (Christensen et al., 2020), among others, used similar descriptions. Table 3-1 provides examples of definitions of “healthy populations” adapted from nutrient recommendation reports of various governmental agencies and other health advocacy organizations. Up through the 1989 RDAs, the primary focus was on preventing dietary deficiency diseases by providing adequate amounts of essential nutrients; individuals with chronic diseases were excluded from the apparently healthy population (NRC, 1989).

Over the past 25 years scientific evidence has evolved that supports the association of dietary intakes with chronic disease risk and increasing availability of dietary guidance for reducing the risk of chronic diseases separate from the RDA process. This led to the recommendation by the Institute of Medicine (IOM) in a 1994 report that future RDAs include guidance on chronic disease risk reduction (IOM, 1994). Despite this, the use of the term “healthy” or “apparently healthy” populations to define the covered population was retained.

Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×

TABLE 3-1 Comparison of Definitions of Intended Populations in Reports on Nutrient Intake Recommendations

Source Definition
U.S. RDAs, 1941 It is understood that these allowances are for persons in health, and that needs may vary markedly in disease. For example, in febrile conditions there is usually an increased need for calories, thiamin, and ascorbic acid. The need for these or other constituents may also be greatly altered in other diseases, especially those of the alimentary tract, which interfere with normal absorption (NRC, 1941, p. 2).
U.S. RDAs, 1953 The allowances are designed for the maintenance of good nutrition of healthy persons in the United States under present conditions (NRC, 1953, p. 1).
British Medical Association, 1950 Quantities of various nutrients recommended “are believed to be sufficient to establish and maintain a good nutritional state in representative individuals of population groups” (British Medical Association, 1950).
U.S. RDAs, 1958 The allowances are planned for healthy, moderately active persons. The presence of acute or chronic illness may modify nutrient requirements markedly. In febrile illnesses and hyperthyroidism, needs for certain nutrients may be enhanced because of increased metabolism, while in other disorders, involving the gastrointestinal tract, absorption of nutrients provided in the diet may be impaired. These problems and the planning of diet for such persons must remain the responsibility of the physician (NRC, 1958).
U.S. RDAs, 1974 RDAs are intake levels of nutrients that meet the needs of healthy people and do not take into account special needs arising from infections, metabolic disorders, chronic diseases, and other abnormalities that require special dietary treatment (NRC, 1974, p. 3).
Canadian RNIs, 1983 RNIs represent intake levels needed to maintain health in already healthy individuals who “eat a variety of common foods available in Canada” (Health and Welfare Canada, 1983).
U.S. RDAs, 1989 RDAs apply to healthy persons. They do not cover special nutritional needs arising from metabolic disorders, chronic diseases, injuries, premature birth, other medical conditions, and drug therapies. Data on the role of diet as a causal or contributing factor in chronic and degenerative disease lead to recommendations derived through approaches different from those used in developing RDAs for specific nutrients (NRC, 1989, p. 20).
U.S./Canadian DRIs, 2000 The DRIs apply to the apparently healthy population. RDAs and AIs are not expected to replete individuals who are already malnourished, nor are they intended to be adequate for those who may have increased requirements because of certain disease states (IOM, 2000, p. 26).
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
UK Scientific Advisory Committee on Nutrition, 2012 [These] are intended only for use in healthy populations and are not intended for individuals or groups that require clinical management (SACN, 2012, p. 82).
EFSA Dietary Reference Values, 2022 DRVs are intended for healthy people. Those who suffer from diseases may have different needs. Health professionals provide guidance to individuals or groups with specific needs (EFSA, 2022).
Nordic Nutrition Recommendation, 2022 The DRVs are intended for healthy individuals. Generally, the DRVs cover increased requirements such as during short-term mild infections or certain medical treatments. The DRVs are usually not suited for long-term infections, malabsorption and various metabolic disturbances, or for treatment of persons with a suboptimal nutritional status. They are meant to be used for prevention purposes (Christensen et al., 2020, p. 11).

NOTE: DRIs = Dietary Reference Intakes; DRVs = Dietary Reference Values; EFSA = European Food Safety Authority; RDAs = Recommended Dietary Allowances; RNIs = Recommended Nutrient Intakes.

The subsequent dilemma for DRI review committees was how to apply the imprecise terminology and definition of terms such as “healthy” or “apparently healthy” populations to DRI values related to chronic disease risk reduction. This issue is particularly relevant given the shift in U.S. and Canadian adult populations so that a majority have, or are at risk of, a chronic disease and thus not considered “healthy.” For example, individuals diagnosed with hypertension or hypercholesterolemia might not be considered healthy but would benefit from reductions in intakes of sodium or substituting unsaturated for saturated fats, respectively. Additionally, many individuals do not maintain a body mass index (BMI) within the recommended range of 18–25 kg/m2, and consequently may or may not be considered as clinically “healthy” (Lloyd-Jones et al., 2022; Petersen et al., 2019). These common conditions contribute to the problem of who should be included in the population for whom the DRIs are intended. The concern about not including the majority of U.S. and Canadian populations and the risk of inconsistencies regarding population groups needs to be considered in future DRIs.

Most weight-related chronic disease data use terminology for overweight and obesity that often is defined by BMI category. Other criteria such as body composition and adipose tissue distribution (adiposity) contribute to comorbidities associated with chronic disease risk (De Lorenzo et al., 2020; Hill et al., 2018) and may be more accurate criteria than BMI alone. However, BMI data are traditionally reported, and this report uses that metric as a proxy for adiposity. A reason to use BMI is that the mea-

Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×

sures are straightforward and consistently applied among investigators. Measures of body composition can vary considerably depending on the method used and calibration of the machine.

Many individuals with diet-related chronic conditions, including those who are treated with some medications, will likely benefit from dietary modifications. These individuals should be included in the population covered by future DRIs, unless there is evidence of an effect of the disease and/or medications on normal physiologic requirements. A strict definition of “healthy” including meeting BMI criteria and eliminating those taking medications for control of chronic disease risk factors would exclude a majority of the U.S. and Canadian adult populations. The goal is to provide dietary recommendations for the broadest segment of the population.

CURRENT HEALTH STATUS OF THE U.S. AND CANADIAN POPULATIONS

A significant proportion of the U.S. and Canadian populations in certain age groups are at risk of developing chronic diseases during their lifetimes or have already been diagnosed with a chronic disease or with risk factors associated with development of these diseases (Table 3-2). The diseases and risk factors commonly linked to poor dietary intakes include, but are not limited to, cardiovascular disease, hypertension, type 2 diabetes, and some cancers. Increasing rates of overweight and obesity are often contributing factors to these risks and diseases. Children who have a BMI for age at the 95th percentile may not demonstrate clinically relevant disease at a young age but are at risk to be on a trajectory that will put them at higher risk of cardiometabolic risk in the future (Christian Flemming et al., 2020; Delvecchio et al., 2020; Drozdz et al., 2021).

Overall trends in obesity for those 20 years of age and older in the United States, collected through the National Health and Nutrition Examination Survey (NHANES), indicate a steady increase in the prevalence of obesity and severe obesity between the 1999–2000 and 2017–2018 collection cycles (Figure 3-1). During this time period, adults with obesity (BMI greater than or equal to 30) increased from 30.5 to 42.4 percent, while those with severe obesity (BMI greater than or equal to 40) increased from 4.7 to 9.2 percent (Hales et al., 2020; Stierman et al., 2021). Children ages 2 to 19 years also showed dramatic increases in obesity (BMI or Z-score1) over the same time period (Figure 3-2).

___________________

1 The Centers for Disease Control and Prevention defines obesity in children as a Z-score > 1.64 and overweight as a Z-score > 1.04 (https://www.cdc.gov/nccdphp/dnpao/growthcharts/resources/modified-z-scores-508.pdf).

Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×

TABLE 3-2 Diseases and Risk Factors Commonly Linked to Dietary Intake

Disease/Risk Factor Population Group Prevalence (percent) Survey Years Source
Obesity U.S. adults > 20 years 42.4 2017–2018 Stierman et al., 2021
U.S. children 2–19 years 19.3 2017–2018 Fryar et al., 2020
Canadian adults ≥ 18 years 27.2 2017–2018 Lytvyak et al., 2022
Canadian children 6–17 years 13.1 2012–2013 Rao et al., 2016
Severe obesity U.S. adults ≥ 20 years 9.2 2017–2018 Fryar et al., 2020
U.S. children 2–19 years 6.1 2017–2018 Fryar et al., 2020
Hypercholesterolemia U.S. adults 40–74 years 27 2007–2010 Kuklina et al., 2013
U.S. adults ≥20 years 25 2015–2018 Arispe et al., 2021
Canadian adults 18–79 years 28 2016–2019 Statistics Canada, 2021
Hypertension U.S. adults: 2017-2018 Arispe et al., 2021
20–44 years 27.5
45–64 years 60.3
≥ 65 years 77.3
U.S. children 8–17 years 3.5 2013–2016 Al Kibria et al., 2019
Canadian adults 20–79 years 22.4 2016–2019 Statistics Canada, 2022
Canadian children 6–18 years 5.8 2007–2015 Robinson et al., 2021
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Image
FIGURE 3-1 Trends in age-adjusted obesity and severe obesity prevalence among adults aged 20 years and over. United States, 1999–2000 through 2017–2018. NOTES: Estimates were age adjusted by the direct method to the 2000 U.S. Census population using the age groups 20–39, 40–59, and 60 and over. Access data table for Figure 3-1 at https://www.cdc.gov/nchs/data/databriefs/db360_tables-508.pdf#4.
1 Significant linear trend.
SOURCES: Hales et al., 2020. Data from National Center for Health Statistics, National Health and Nutrition Examination Survey, 1999–2018.

In Canada, the most recently reported prevalence of obesity is lower than for the United States at 27 percent for adults and 13 percent for children age 6 to 17 years (Table 3-2). Obesity and overweight are generally associated with an increased risk of all-cause mortality across adult age groups (Twells et al., 2022). As an outcome of unhealthy dietary choices, inadequate access to healthy foods, and lifestyle factors, a large and increasing proportion of the general population is at elevated risk of chronic disease or has been diagnosed with chronic disease risk factors such as hypercholesterolemia, hypertension, or hyperglycemia. Although data on such risks is limited, the issue should not be ignored. Obesity and overweight in childhood and adolescence will likely lead to obesity-related health outcomes in adulthood (USPSTF et al., 2017).

The DRIs are intended for populations that now include a high proportion of individuals with chronic disease risk factors or established diseases that often require medication use. Chronic disease risk factors and the use of medications are common, particularly among middle-aged

Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Image
FIGURE 3-2 Trends in obesity among children and adolescents, aged 2–19 years, by age. United States 1963/1965 through 2017/2018.
NOTE: Obesity is body mass index (BMI) at or above the 95th percentile from the sex-specific BMI-for-age 2000 CDC Growth Charts.
SOURCES: Fryar et al., 2020. Data from National Center for Health Statistics, National Health Examination Surveys II (ages 6–11), III (ages 12–17); and National Health and Nutrition Examination Surveys (NHANES) I–III, and NHANES 1999–2000, 2001–2002, 2003–2004, 2005–2006, 2007–2008, 2009–2010, 2011–2012, 2013–2014, 2015–2016, and 2017–2018.

and older adults (Table 3-3). Individuals with chronic diseases or chronic disease risk factors should be considered as part of the general population unless there is an effect of the disease and/or medications on nutritional status that would alter normal physiologic requirements. In contrast, persons with existing conditions that clearly are known to alter nutrient metabolism or requirements, or those being treated with medications that alter nutrient metabolism, should not be included in the general population for the DRIs specific to those nutrients.

Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×

TABLE 3-3 Use of Medications by Adults with Hypercholesterolemia and Hypertension in the United States and Canada

Chronic Disease Population Group/Age Medication Use (percent) Survey Years Source
Hypercholesterolemia U.S. adults: 2007–2010 Kuklina et al., 2013
40–64 years 19
65–74 years 39
Canadian adults: 2016-2019 Statistics Canada, 2021
40–59 years 10
60–79 years 34
Hypertension U.S. adults: 2011–2014 Muntner et al., 2018
55–64 years 17.4
65–74 years 11.0
Canadian adults: 2012–2015 Statistics Canada, 2021
40–59 years 23.2
65–69 years 46.6
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
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Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 10
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 11
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 12
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 13
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 14
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
Page 15
Suggested Citation:"3 Defining the DRI Population." National Academies of Sciences, Engineering, and Medicine. 2022. Defining Populations for Dietary Reference Intake Recommendations: A Letter Report. Washington, DC: The National Academies Press. doi: 10.17226/26733.
×
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Since 1997, the United States and Canada have adopted harmonized Dietary Reference Intakes (DRIs), a set of nutrient intake reference values for use in planning and assessing diets for individuals and groups in both countries. In 2022 the U.S. Department of Agriculture asked the National Academies of Sciences, Engineering, and Medicine to convene a Standing Committee to review the DRI framework, including the structure and process that will guide future DRI reviews, and respond to questions posed by the U.S. and Canadian Federal DRI working group. Dietary recommendations have traditionally been designed for populations that were referred to as healthy or apparently healthy. The imprecise terminology and definition of these terms may exclude the increasing number of American and Canadian citizens with chronic disease. In its first letter report, the Standing Committee offers its advice on how to define the population to be considered for DRI recommendations for the United States and Canada.

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