Food and Nutrition Bulletin

Although most countries and regions around the world set recommended nutrient intake values for their populations, there is no standardized terminology or framework for establishing these standards. Different terms used for various components of a set of dietary standards are described in this paper and a common set of terminology is proposed. The recommended terminology suggests that the set of values be called nutrient intake values (NIVs) and that the set be composed of three different values. The average nutrient requirement (ANR) reflects the median requirement for a nutrient in a specific population. The individual nutrient level (INL_x) is the recommended level of nutrient intake for all healthy people in the population, which is set at a certain level x above the mean requirement. For example, a value set at 2 standard deviations above the mean requirement would cover the needs of 98% of the population and would be INL₉₈. The third component of the NIVs is an upper nutrient level (UNL), which is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in a specified life-stage group. The proposed framework for deriving a set of NIVs is based on a statistical approach for determining the midpoint of a distribution of requirements for a set of nutrients in a population (the ANR), the standard deviation of the requirements, and an individual nutrient level that assures health at some point above the mean, e.g., 2 standard deviations. Ideally, a second set of distributions of risk of excessive intakes is used as the basis for a UNL.

Upper levels are estimates of the quantity of a nutrient that can be ingested daily over a lifetime without appreciable risk to health. The approach to establishing upper levels for nutrients, nutrient risk assessment, has derived from the risk assessment of foreign chemicals that are deliberately added to foods, or are in food as contaminants. This process of risk assessment is rigorous and transparent, particularly in dealing with the uncertainty arising from the data available and their assessment and extrapolation to human populations. Hazard identification and characterization, i.e., a dose—response pattern, as applied to xenobiotics, are discussed first, and then the difficulties of applying this approach to nutrients are reviewed. Nutrients, in contrast to foreign chemicals, have specific and selective metabolic pathways and homeostasis, as well as specific functions. This is the source of differences in the nutrient risk assessments produced by various national and international advisory bodies. Although the same data are used in such exercises, different judgments are made about identifying adverse effects, the nature of uncertainties in the assessment, and in matching the upper levels with exposure assessments and dietary reference values. The establishment of different upper levels for different national and international communities is a source of confusion in public health policy and practice and a barrier to trade. It is proposed that a basis for harmonizing the existing approaches used in nutrient risk assessment would be the collaborative development of the model for establishing upper levels of intake for nutrients and related substances that has been recently described by a Joint Task Force of the World Health Organization and the Food and Agriculture Organization.

One of the most important of the nutrient intake values (NIVs) is the average nutrient requirement (ANR). The ANR is defined as an intake value that will be adequate for half of the individuals in a group of people with similar characteristics. It is used to estimate the prevalence of adequacy, and it serves as the basis for the individual nutrient level (INL_x). The determination of adequacy is a complex process, with the resulting value of the ANR dependent on the criterion or functional outcome chosen to define nutrient adequacy. Because nutrients have multiple sites of action in human metabolism, it is possible to demonstrate abnormal function in one parameter measured or observed as a result of inadequate intake of a nutrient, while other parameters requiring the same nutrient appear normal or within normal ranges. Thus, depending on the criterion of adequacy selected, the requirement for a given nutrient may be at a lower or a higher intake amount. In harmonizing development of NIVs, it is important to clearly identify the criterion of adequacy selected and the rationale for its selection. Rarely are available data sufficient to provide dose—response information from which to select a level of intake at which half of the individuals demonstrate adequacy and half appear to demonstrate inadequacy. Three levels of intake, of which at least one level of intake is below the requirement for most of the individuals in the sample, and one level of intake is above their requirement, are useful for establishing a level at which half of the group might be considered to demonstrate adequacy. Types of human nutrient studies that may be used to obtain data are discussed, as well as characteristics of the sample size needed to demonstrate adequacy. The variation in requirements is also an important aspect in predicting levels of intake that will have defined probabilities of adequacy for groups (to develop the INL_x, where x is the defined probability chosen). An analysis of the origins of different types of variability is presented. When estimating energy requirements, a special case of NIVs, important issues must be considered. Additionally, an example of evaluating data used to establish an ANR for vitamin A, and the effect of variability in requirements for vitamin A, is provided.

This article describes the methods for using nutrient intake values (NIVs) to plan and assess intakes of both individuals and population groups. The advantages of the more recent standards, which use an average nutrient requirement (ANR) and its standard deviation to describe the distribution of nutrient requirements, are highlighted. The goal of assessing the intake of an individual is to determine the probability that the person's usual diet is meeting his or her nutrient needs and whether the person is at risk for adverse effects from excessive intakes, whereas the goal of planning an individual's intake is to ensure that the probability of inadequate intake and the likelihood of excessive intake are both small. The goal of assessing intakes of groups is to determine the prevalence of inadequate intakes and the prevalence of potentially excessive intakes, whereas the goal of planning nutrient intakes for groups is to minimize the prevalence of inadequate intakes and also to minimize the prevalence of potentially excessive intakes. For all of these goals, it is important to utilize appropriate food-composition tables and accurate dietary assessment methods. To fully utilize the new paradigm, it will be necessary for the professional nutrition community to identify ways to implement these new procedures in nutrition research and nutrition programs, to describe the strengths and weaknesses of the results, and to contribute to the evolution of both the theory and the application of the NIVs when planning and assessing diets.

The derivation of reference values in 11 current dietary reference standards is often based on methods of extrapolation or interpolation, but these are not consistent across reports. Such methods are frequently employed to derive nutrient intake values (NIVs) for infants and children owing to the paucity of relevant research data available. The most common method is to extrapolate values for children down from those of adults, employing a weight or metabolic factor and adjusting for growth. In some instances, values for young children are extrapolated up from infants, values for adults are extrapolated up from children, or values for older adults are extrapolated up from young adults. Extrapolation is employed to estimate not only nutrient requirement or adequate intake but also the upper tolerable levels of intake. Extrapolation methods may also form the basis of estimates of tissue deposition of nutrients during growth in children and for the maternal/fetal dyad in pregnancy with adjustments for metabolic efficiency. Likewise, recommended intakes during lactation are extrapolated from known secretion of the nutrient in milk with adjustments for bioavailability. For future dietary standards, a first priority is to obtain relevant scientific data using current methodology, such as stable isotope tracers, body composition analysis, and appropriate biomarkers, from which NIVs for each age group can be derived. Extrapolation to derive an NIV is only acceptable in the sheer absence of sound scientific data and must be modeled with a consistent approach. For the purpose of harmonization of dietary standards, we recommend the following approaches that should be clearly described in reports: standardization of age groups on a biological basis (growth and pubertal stages) with consideration of relevant developmental milestones throughout childhood; application of internationally accepted standards for growth, body size, body composition, fetal and maternal nutrient accretion in pregnancy, and milk composition; and inclusion of appropriate adjustments (metabolic efficiency, weight change, or physical activity).

To convert physiological requirements into dietary requirements, adjustments are needed for some nutrients that take into account certain diet- and host-related factors specific to a country or region. Nutrients whose requirements should be adjusted in this way include calcium, magnesium, iron, zinc, protein, folate, vitamin A, and carotenoids. The diet-related factors that must be considered depend on the nature of the habitual diet and may include the chemical form of the nutrient and the nature of the dietary matrix, interactions between nutrients and/or organic components, and food preparation and processing practices within the country or region. The host-related factors can be further subdivided into intestinal and systemic factors. Reductions in the secretion of hydrochloric acid, gastric acid, and/or intrinsic factor, together with alterations in the permeability of the intestinal mucosa, are all examples of intestinal factors that can markedly influence the absorption of certain nutrients, but that are often ignored when setting dietary requirements. Systemic factors that should also be considered include nutrient status of the host, age, sex, ethnicity, genotype, and physiological state (e.g., pregnancy or lactation), and chronic and acute infectious disease states. Algorithms can estimate the bioavailability of iron, zinc, protein, folate, vitamin A, and carotenoids, although their accuracy is limited by the complex interactions among the absorption modifiers in the whole diet. For calcium and magnesium, the amount available for absorption is still estimated from their major food sources in the habitual diet. Currently, there are often large differences in the adjustments employed to convert physiological requirements to dietary requirements, even among countries consuming diets of similar patterns.

Human genetic variation is a determinant of nutrient efficacy and of tolerances and intolerances and has the potential to influence nutrient intake values (NIVs). Knowledge derived from the comprehensive identification of human genetic variation offers the potential to predict the physiological and pathological consequences of individual genetic differences and prevent and/or manage adverse outcomes through diet. Nutrients and genomes interact reciprocally; genomes confer differences in nutrient utilization, whereas nutrients effectively modify genome expression, stability, and viability. Understanding the interactions that occur among human genes, including all genetic variants thereof, and environmental exposures is enabling the development of genotype-specific nutritional regimens that prevent disease and promote wellness for individuals and populations throughout the life cycle. Genomic technologies may provide new criteria for establishing NIVs. The impact of a gene variant on NIVs will be dependent on its penetrance and prevalence within a population. Recent experiences indicate that few gene variants are anticipated to be sufficiently penetrant to affect average requirement (AR) values to a greater degree than environmental factors. If highly penetrant gene variants are identified that affect nutrient requirements, the prevalence of the variant in that country or region will determine the feasibility and necessity of deriving more than one AR or upper limit (UL) for affected genetic subgroups.

The process of applying nutrient intake values (NIVs) for dietary assessment, planning, and implementing programs is discussed in this paper. In addition to assessing, monitoring, and evaluating nutritional situations, applications include planning food policies, strategies, and programs for promotion of optimal nutrition and preventing and treating malnutrition (both over- and undernutrition). Other applications include nutrition education, food and nutrient legislation, marketing and labeling, research, product development, food procurement and trade (import and export), food aid, and therapeutic (clinical) nutrition. Specific examples of how NIVs are used to develop food labels, fortification policies, and food-based dietary guidelines are described. Applications in both developed and developing countries are also described. In summary, NIVs are the scientific backbone of all aspects of nutrition policy in countries and regions worldwide.

Trade in food and animal products has increased several-fold in the past decade, and simultaneously regulations governing the movement of such products across national boundaries have also increased. The present study reviews harmonization in food trade regulation by focusing on nutritional aspects to understand its role in enhancing world trade on the one hand and consumer interest and welfare on the other. Harmonization to a large extent brings in more regulation from the developed world acting through their governments, consumer organizations, and multinational companies; it does not seem to address, in general, the concerns of the large segments of the poor population for whom agriculture and food trade are the main sources of livelihood. There is a lack of quantifiable estimates of the loss in well-being of the disadvantaged. However, there is substantial research focused on the potential harm to developed nations as a result of nonadherence to the rules. Clearly, lack of adequate infrastructure, resource constraints, and weak institutions not only result in poor food safety regulation within developing countries but also remain barriers to realizing the greater potential benefits from increased trade. Harmonization of standards would have some losers and some winners, but to make it more inclusive, scientific knowledge alone may not be adequate; social and cultural aspects also need to be considered, since food systems differ among regions, with varying preferences, local resource availability, and levels of economic development. Improvement in governance in many countries not only would ensure better participation in international rule-making and the negotiation process for fairer trade but also would result in effective domestic legislation to ensure safer health for citizens, resulting in higher overall well-being.

To reduce the increased burden of diet-related disease and promote human potential through food and nutrition globally, harmonization of efforts is urgently needed. This article examines the concept of food-based dietary guidelines (FBDGs) and discusses the possibilities and challenges of harmonizing the process of developing and implementing dietary guidelines. The authors argue that while the development of FBDGs has contributed to the understanding of the role of nutrients and foods in achieving optimal health, the impact of these guidelines on human health has been limited.

Science or evidence must be used in FBDG development; nevertheless, there are limitations in current nutrition science. FBDGs should address the health consequences of dietary insufficiency, excess, or imbalance with a broader perspective, considering the totality of the effects of a given dietary pattern, rather than focusing on single nutrients alone. Moreover, the food selection guideline should be seen as complementary to a strategic, comprehensive, and culturally appropriate dietary and health promoting intervention, and not only as a tool for providing nutrition policy and information.

Technically, a single unified global set of FBDGs may be desirable and even achievable. This concept, however, presents novel challenges on how to address cultural diversity and the complex social, economic, and political interactions between humans and the food supply, not to mention the complexity of its communication and implementation. Therefore, global harmonized efforts in support of strategic dietary interventions, together with strong global scientific support and facilitation for the development and communication of FBDGs at national or regional levels, are proposed to implement FBDGs for healthier populations.