Nutrient Reference Values (NRVs) list the recommended intakes for energy (kilojoules), protein, fats, carbohydrate, fibre, vitamins, minerals and fluid, based on age, sex and life stages. They are used by dietitians, nutritionists and other health professionals to assess the dietary needs of individuals and groups (such as residents of nursing home or pupils in boarding schools). The NRVs are revised from time to time to reflect the latest scientific research.
Australia and New Zealand has figures for 33 essential nutrients (protein, vitamins, minerals, etc) which were published in 2006 by the National Health and Medical Research Council (NHMRC). They replace the earlier set of Recommended Dietary Intakes (RDIs) which dated back to 1991.
Five different values
In place of the older single-figure values, the 2006 NRVs embrace five different values for each nutrient. These are:
1. Estimated Average Requirement (EAR)
A daily nutrient intake level needed to meet the requirements of half the healthy individuals in a particular age, life stage or gender.
2. Recommended Dietary Intake (RDI)
The average daily intake of nutrients (from foods not supplements) that is sufficient to meet the needs of nearly all (97–98 per cent) healthy individuals in a particular life stage , age group or gender group. The RDIs are derived from the EAR. They include a margin of safety to cover individual differences.
It's the RDIs that you hear about most often. They are used for education, planning clinical diets, formulating meal replacements and fortified foods, monitoring food supplies, checking the adequacy of rations, and labelling on foods packaging.
The terminology differs from country to country—in the US it is known as Dietary References Intakes and Recommended Dietary Allowances, and in the UK it is Recommended Nutrient Intakes.
3. Adequate Intake (AI)
This number is used when an RDI cannot be determined. It represents the average daily nutrient intake by a group of apparently healthy people known not to have a deficiency that we can assume is adequate.
4. Upper Limit (UL)
This is the highest average daily intake likely to pose no adverse health effects to almost all individuals in the general population.
5. Suggested Dietary Targets (SDTs)
These are higher intakes that may prevent or reduce the risk of chronic disease such as heart disease, certain cancers or high blood pressure.
In addition, you'll find the Estimated Energy Requirement (EER) which is the average amount of energy (kilojoules) predicted to maintain weight and good health for an adult for a given age, gender, weight, height and level of physical activity.
How the NRVs works
It looks complicated, I know, but here's an example of how the NRVs work in practice. Take the mineral iron as an example which is needed for healthy blood, immune function and brain development in toddlers and children. The recommendations for daily iron intake (from both food and supplements) for good health for women aged 19 to 50 look like this:
- RDI of 18 mg—the average daily dietary intake to aim for
- EAR of 8 mg—this is the bare minimum a woman needs
- UL 45 mg— this is a safe maximum so you don't overload your body.
In contrast, we know a lot less about copper, a trace mineral. There is no EAR set and therefore no RDI. But there is an AI of 1.2 mg for women, based on the best research published.