Food First: How to Read Reference Intakes, RDAs and Label Percentages

Nutrition · Published 2026-10-24

Supermarket shelves stocked with peppers, leafy greens, celery and carrots — Fresh vegetables on supermarket shelves.

An RDA, a PRI, an RNI, a %DV, an NRV: nutrition comes with an alphabet of numbers. Once you know what each one means, labels become easier to read, and it becomes clearer why "100%" on a supplement says little about whether you need it.

Reference values are for populations

Dietary reference values are set by expert panels to plan and assess the diets of groups of healthy people. They are built from a distribution: people's requirements vary, so panels estimate the average requirement and then set a higher figure that covers nearly everyone. Because the higher figure is designed to cover people with the highest needs, most people need less than it. A single day's intake below the reference value is not a deficiency; reference values describe average intakes over time.

The US terms (Dietary Reference Intakes)

EAR (Estimated Average Requirement): the intake that meets the needs of half the healthy people in a group.
RDA (Recommended Dietary Allowance): the intake sufficient for nearly all (97 to 98%) healthy people in a group. It is usually the EAR plus two standard deviations.
AI (Adequate Intake): used when there is not enough evidence to set an EAR and RDA. It is based on observed intakes of apparently healthy people and is assumed to be adequate.
UL (Tolerable Upper Intake Level): the highest average daily intake likely to pose no risk of adverse effects. See upper limits.

These values are set by the National Academies of Sciences, Engineering, and Medicine and are presented, nutrient by nutrient, in the fact sheets of the NIH Office of Dietary Supplements.

The EU terms (EFSA)

EFSA uses parallel concepts: the AR (average requirement, equivalent to the EAR), the PRI (population reference intake, equivalent to the RDA), the AI (adequate intake) and the UL. EFSA has published opinions nutrient by nutrient since 2010 and makes them searchable in its online DRV finder. Individual EU countries may also have national values.

The UK terms

The UK uses values largely set by the Committee on Medical Aspects of Food Policy (COMA) in 1991, with updates by the Scientific Advisory Committee on Nutrition (SACN), for example for vitamin D in 2016:

EAR: estimated average requirement;
RNI (Reference Nutrient Intake): enough for 97.5% of people, equivalent to the RDA;
LRNI (Lower Reference Nutrient Intake): enough for only the 2.5% of people with the lowest needs. Habitual intakes below the LRNI suggest that most people in a group are likely to be getting too little.

Why the numbers differ between countries

Readers are often surprised that vitamin C for men is 40 mg a day in the UK, 90 mg in the US and 110 mg in the EU. The differences are not mistakes. Panels choose different criteria (preventing deficiency signs, maintaining a biomarker, saturating tissues), review the evidence at different dates, and make different assumptions about absorption, sun exposure or body size. Each of these figures is a defensible estimate. What matters is that each is used consistently within its own system.

Nutrient (adult men)	UK RNI	US RDA/AI	EFSA PRI/AI
Vitamin C	40 mg	90 mg	110 mg
Vitamin B12	1.5 mcg	2.4 mcg	4.0 mcg (AI)
Vitamin D	10 mcg	15 mcg	15 mcg (AI)
Iron	8.7 mg	8 mg	11 mg
Magnesium	300 mg	420 mg (31+)	350 mg (AI)

Reading labels: %DV and %NRV

Labels do not use the full tables above; they use a single reference figure per nutrient.

United States: Daily Value (DV). US labels show "% Daily Value". Under the updated FDA rules, the DV for adults and children four and over is, for example, 20 mcg of vitamin D, 18 mg of iron, 2.4 mcg of vitamin B12, 90 mg of vitamin C, 420 mg of magnesium and 400 mcg DFE of folate. A DV is a single labelling figure, often set at the highest RDA among adult groups.
EU and UK: Nutrient Reference Value (NRV). Under EU Regulation 1169/2011 (retained in UK law), labels state vitamins and minerals as a percentage of the NRV. Examples: vitamin D 5 mcg, vitamin C 80 mg, vitamin B12 2.5 mcg, folic acid 200 mcg, iron 14 mg, magnesium 375 mg. Some of these are older figures and differ from EFSA's current reference values; vitamin D, at 5 mcg, is notably lower than current advice.

Because of these differences, a vitamin D supplement that provides 10 mcg is "200% NRV" on a European label and "50% DV" on an American one. The percentage depends on the reference figure, not on your needs.

Food first

National dietary guidelines (the UK Eatwell Guide, the Dietary Guidelines for Americans and their European equivalents) aim to meet nutrient needs mainly through food: vegetables and fruit, wholegrains, pulses, nuts and seeds, dairy or fortified alternatives, fish, and moderate amounts of meat. Food provides fibre and many compounds that supplements do not, and it is very difficult to reach a harmful intake of a vitamin from ordinary foods (liver and vitamin A in pregnancy being an exception). Supplements are recommended for particular nutrients and groups where food alone is not enough, which the next page covers: who may need supplements.

In short

RDA (US), PRI (EU) and RNI (UK) are set to cover nearly everyone; most people need less.
Values differ between countries because of different methods, not errors.
Label percentages (%DV, %NRV) use single reference figures and do not tell you whether you personally need a supplement.
Official guidance is food first, with targeted supplements where needed.

This page is general information, not medical advice. For personal dietary advice, consult a registered dietitian or your doctor.

Sources

NIH Office of Dietary Supplements, Nutrient recommendations and databases.
EFSA, Dietary reference values finder.
Public Health England, Government dietary recommendations (2016).
US Food and Drug Administration, Daily Value on the Nutrition and Supplement Facts labels.
Regulation (EU) No 1169/2011 on the provision of food information to consumers, Annex XIII.