Dietary Reference Intakes

Dietary reference intakes (DRIs) are a set of quantitative reference values for nutrient intake used to plan and assess the diets of healthy populations and groups. They extend the older concept of a single recommended dietary allowance into a family of values, each defined for a different purpose, and they form the scientific foundation on which food-based dietary guidelines and nutrition policy are built.

Definition

Dietary reference intakes are a coordinated set of nutrient reference values, including an estimated average requirement, a recommended intake that covers the needs of nearly all healthy individuals, an adequate intake used when data are limited, and a tolerable upper intake level, used to assess and plan diets of populations and groups.

Scope

The topic covers the main reference values and what each is for, how they are derived from the distribution of nutrient requirements, and how they are applied to assessing and planning intakes for groups rather than to diagnosing individuals. It is a reference and educational topic and does not provide individual dosing or supplementation advice.

Core questions

• How is the requirement distribution for a nutrient estimated, and how does it yield the reference values?
• What is the difference between the estimated average requirement and the recommended intake?
• When is an adequate intake used instead of a requirement-based value?
• How should reference intakes be applied to groups rather than to individuals?

Key concepts

• Estimated Average Requirement (EAR)
• Recommended Dietary Allowance / Recommended Nutrient Intake
• Adequate Intake (AI)
• Tolerable Upper Intake Level (UL)
• Requirement distribution and population coverage
• Assessing versus planning intakes
• Reference values for groups versus individuals

Mechanisms

A reference intake begins with an estimate of the average requirement for a nutrient in a defined population group, derived from balance studies, biomarkers, or experimental data. Assuming a distribution of requirements, the recommended intake is set above the average so that it meets the needs of nearly all healthy individuals in the group. When the evidence is too sparse to define a requirement, an adequate intake based on observed consumption of healthy populations is used instead, and a tolerable upper intake level marks the level above which the risk of adverse effects rises. These values are designed for assessing and planning diets of groups, where the goal is a low prevalence of inadequate or excessive intake.

Clinical relevance

Reference intakes underpin the nutrient targets used in dietary assessment, food labelling reference values, and public health programmes, so understanding them helps practitioners read and apply national guidance. They describe population reference standards and are not a basis for prescribing nutrient amounts to an individual.

Epidemiology

Reference intakes are used to estimate the prevalence of inadequate or excessive nutrient intake in populations, informing the design of fortification, supplementation, and guideline programmes. The historical case of folic acid illustrates how trial evidence on neural tube defect prevention fed into reference values and population policy.

History

The recommended dietary allowance concept arose in the mid-twentieth century to prevent deficiency diseases by specifying a single adequate intake per nutrient. Over later decades this was expanded into the broader dietary reference intake framework, which separates the average requirement from the population-coverage value and adds upper limits, reflecting a shift from preventing deficiency alone toward also avoiding excess.

Debates

How should reference values handle uncertainty in the requirement distribution?

Because the shape and variance of nutrient requirement distributions are often poorly known, there is ongoing discussion about how conservatively to set recommended intakes and upper limits, and when to fall back on adequate-intake values.

Seminal works

• iom-dri-2006
• mrc-1991

Frequently asked questions

What is the difference between the EAR and the recommended intake?

The estimated average requirement is the intake that meets the needs of half the individuals in a group, while the recommended intake is set higher so that it covers the needs of nearly all healthy individuals; the EAR is the value used to assess the adequacy of group intakes.

Are dietary reference intakes meant to be applied to a single person?

They are designed primarily for assessing and planning the diets of populations and groups; applying them to an individual is approximate, because any one person's true requirement is unknown.