The European Commission has requested EFSA to review the existing advice of the Scientific Committee on Food on Population Reference Intakes for energy, nutrients and other substances with a nutritional or physiological effect. These reference values date from 1993. Since then new scientific data have become available for some of the nutrients, and scientific advisory bodies in many European Union Member States and in the United States have reported on recommended dietary intakes.
This Opinion focuses on the general principles for development and application of Dietary Reference Values (DRVs) - quantitative reference values for nutrient intakes for healthy individuals and populations which may be used for assessment and planning of diets.
Similarly to the earlier Scientific Committee on Food (SCF) report in 1993 the Panel proposes to derive the following Dietary Reference Values:
- Population Reference Intakes (PRI): the level of (nutrient) intake that is adequate for virtually all people in a population group.
- Average Requirement (AR): the level of (nutrient) intake that is adequate for half of the people in a population group, given a normal distribution of requirement.
- Lower Threshold Intake (LTI): the level of intake below which, on the basis of current knowledge, almost all individuals will be unable to maintain “metabolic integrity”, according to the criterion chosen for each nutrient.
In addition, the Panel also proposes to derive the following Dietary Reference Values:
- Adequate Intake (AI): the value estimated when a Population Reference Intake cannot be established because an average requirement cannot be determined. An Adequate Intake is the average observed daily level of intake by a population group (or groups) of apparently healthy people that is assumed to be adequate.
- Reference Intake ranges for macronutrients (RI): the intake range for macronutrients, expressed as % of the energy intake. These apply to ranges of intakes that are adequate for maintaining health and associated with a low risk of selected chronic diseases.
The Panel will not address the Tolerable Upper Intake Level (UL) as this has been assessed previously. The Tolerable Upper Intake Level is the maximum level of total chronic daily intake of a nutrient (from all sources) judged to be unlikely to pose a risk of adverse health effects to humans.
Some of the Reference Values - the Average Requirement, Population Reference Intake and the Lower Threshold Intake - relate to nutrient requirements that are defined by specific criteria of nutrient adequacy. In defining nutrient requirements the selection of criteria to establish nutrient adequacy is an important step. For most nutrients a hierarchy of criteria for nutrient adequacy can be established, ranging from prevention of clinical deficiency to optimisation of body stores, or status. Which criterion, or combination of criteria, will be the most appropriate will be decided on a case-by-case basis.
Within any lifestage group, nutrient requirements vary between individuals and the Average Requirement, Population Reference Intake and Lower Threshold Intake represent different points on the distribution of individual requirements. Nutrient requirements also differ with age, sex and physiological condition, due to differences in the velocity of growth for the younger age groups, and age-related changes in nutrient absorption and body functions and/or functional capacity, such as renal function. Especially in older subjects, variability in functional capacity and in energy expenditure appears higher than in younger adults, particularly for elderly above 75 years.
Because of this, Dietary Reference Values are developed for different life stage and sex groups. The Panel proposes to define the age ranges used for each nutrient on a case-by-case basis depending on the available data. For the age group <6 months requirements are considered to be equal to the supply from breast-milk, except on a case-by-case basis where this does not apply. Separate reference values will be established for pregnant and lactating women, taking into account the additional nutrient requirement for the formation of new tissues, or to compensate for the nutrients lost to the body in the form of human milk, respectively, and considering the physiological adaptations that occur during these conditions.
Interpolation or extrapolation between population groups will be used in instances where no data are available for defined age and sex groups. Scaling methods using isometric (linear with body weight) or allometric (body weight to the power of a chosen exponent) or interpolation based on other non predefined parameters are being used. Which method is the most appropriate will be decided on a case-by-case basis.
Reference heights and weights are useful when more specificity about body size and nutrient requirements are needed than that provided by life stage categories. In the absence of more recent data, reference weights will be the same as in the SCF report, and for children <1 year, as established by the WHO for fully breastfed infants.
Dietary reference values can be used for different purposes, such as in diet assessment and diet planning, both at the population and individual level, but also as a basis for reference values in food labelling, and in establishing food based dietary guidelines.
In dietary assessment of groups the Average Requirement can be used to estimate the prevalence of inadequate intakes of micronutrients (the Average Requirement cut-point method), if the distribution of nutrient intakes is normal, and intakes are independent from requirements. The Population Reference Intake should not be used for this purpose as this would result in overestimation of the proportion of the group at risk of inadequacy. Probabilistic methods, taking into account both the intake and requirement variation might be used as an alternative, and in case distributions are skewed.
For macronutrients with a defined reference intake range for individuals, the distribution of usual intake of individuals may be assessed to ascertain what proportion of the group lies outside the reference lower and upper limits of the range. In case of energy, the mean usual intake of energy of a defined group, relative to the average requirement, may be used in assessing the adequacy.
For assessment of adequacy of nutrient intakes in individuals Dietary Reference Values are of limited use. Usual intakes below the AR are likely inadequate, and below the Lower Threshold Intake very probably inadequate, while chronic intakes above the Tolerable Upper Intake Level may be associated with an increased risk of adverse effects. For a valid assessment of the adequacy of an individual's usual intake, combined information with anthropometric, biochemical (status) and clinical data is needed.
In dietary planning for groups the usual intake distribution should be between the AR and UL to avoid inadequate, respectively excessive intakes. For nutrients such as vitamins, minerals, and protein, the PRI can be a practical starting point. However, target median intakes higher than the Population Reference Intake might be considered, especially in case of a skewed intake distribution. For macronutrients the distribution of usual intake of individuals should be such as to minimise the proportion of the group that lies outside the reference lower and upper limits of the range. For energy, the reference intake (estimated average energy requirement) of the group based on sex, age, height, weight, and physical activity level of the group may be used as a planning goal.
The goal of planning diets for individuals is to have a low probability of inadequacy while minimising potential risk of excess for each nutrient. For nutrients such as vitamins, minerals, and protein, this is done by ensuring that the usual intake meets the Population Reference Intake or Adequate Intake while not exceeding the Tolerable Upper Intake Level. Population Reference Intakes would be an overestimation for most individuals. For macronutrients which have a reference intake range, the usual intake of individuals should be between the lower and upper bounds of the reference range. For energy, the reference intake (average energy requirement) based on an individual’s sex, age, height, weight, and physical activity level may be used as an initial planning goal; however, body weight must be monitored and intake adjusted as appropriate.