The project to develop and publish the new Nutrient Reference Values (NRVs) for Australia and New Zealand has been a joint project between the Commonwealth Department of Health and Ageing and the Ministry of Health. The project has been managed by the National Health and Medical Research Council of Australia (NHMRC). The project was initiated in 2002 and used the most recent US and Canadian Dietary Reference Intakes as a starting point. Public consultation was undertaken in Australia and New Zealand during late 2004 and early 2005. Following amendments, the draft document underwent independent review before adoption by the NHMRC and the Ministry of Health.
NRVs refer to the levels of recommended intakes of essential nutrients, such as vitamins and minerals. The NRVs differ from the previous 1990 Australian Recommended Dietary Intakes as they include more nutrients (36 plus energy), a range of levels for different purposes, and provide advice on reducing risk of chronic disease. However, NRVs do still include a level known as the recommended dietary intake (RDI), which is the average daily intake level of a particular nutrient that is sufficient to meet the requirements of nearly all healthy individuals in a particular life stage and gender group.
The new NRVs consist of three technical documents: an executive summary (88 pages, primarily a summary of the tables), the main document (344 pages, includes discussion of each nutrient and all the recommendations), and the evidence appendix (269 pages, which rates the strength of the evidence for the recommendations for each nutrient).
Additional background information on the Nutrition Reference Values
1. What is different about these recommendations?
- cover a much wider range of nutrients than earlier recommendations (eg, long chain omega 3 fats, dietary fibre, water, vitamin K, fluoride)
- include a set of values for each nutrient (instead of a single value). These values address the daily needs of individuals or groups in the community for maintenance of normal function and prevention of deficiency (ie, Estimated Average Requirement; Recommended Dietary Intake or Adequate Intake) or excess (Upper Level of Intake)
- include additional recommendations about intakes of certain nutrients that may reduce the risk of chronic disease such as heart disease, certain cancers or high blood pressure.
2. Compared to the old RDIs, which nutrients have significantly changed recommendations and why?
As noted above, there are some nutrients that have not previously had a recommended intake level. For other nutrients, there have been some increases in recommended intakes notably for folate and other B vitamins (thiamin, niacin, riboflavin, vitamin B6 and B12) as well as calcium and magnesium.
The increase in the B vitamin reference values generally reflects the ways they were set in the earlier version. In the 1981-89 RDIs, the values for B vitamins were generally set in relation to energy or protein needs which, in turn, were set on figures recommended at that time by the FAO: WHO. The EARs for B vitamins in this set of reference values were set using results of metabolic studies with specific biochemical endpoints in blood, tissues or urine related to potential deficiency states or on the results of depletion-repletion studies.
The new increased recommendations for folate are based on new data looking at dietary intake in relation to maintenance of plasma and red blood cell folate, and homocysteine level. Whilst the recommendation may appear at first glance to have doubled, it is expressed in terms of “dietary folate equivalents” in recognition of the difference in bioavailability between food folate and folic acid. Folic acid is the form used for food fortification and in dietary supplements, which is twice as well absorbed as food folate.
In relation to calcium the difference between the old RDI and the new relates almost entirely to the recognition that there are losses through sweat of some 60mg/day not accounted for in previous estimates.
In the case of magnesium, the new EAR/RDIs are based on maintenance of whole body magnesium over time from balance studies mostly published since the last Australian RDIs were set. There were limited data at the time the last RDIs were set which gave a wide range of estimates of need.
3. Is there a way of calculating the new values from the old values?
No, there is no way of calculating the new values from the old. There has been a great deal of new information produced since the last revision. For some nutrients this has led to only minor changes in the recommendations, for others, the changes are more substantial.
4. Why are there different values for some nutrients for deficiency disease and chronic disease.
Different values have been set for some nutrients for prevention of ‘deficiency’ states versus prevention of chronic disease as the nature and certainty of the evidence for these two end points differs.
Physiological needs for the prevention of deficiency states in humans can generally be more clearly defined than physiological needs for chronic disease prevention. It is possible to design controlled experiments in human volunteers to look at what levels of daily intake are required to maintain a certain level of the nutrient or a marker for deficiency in blood or body tissues and/or to prevent a specific clinical deficiency disease (eg, scurvy in the case of vitamin C).
Data about the links between diet and chronic disease usually depend on population or epidemiological studies of food or nutrient intake and their link with increased ‘risk’ of disease. There are limited nutrient intervention trials and these generally use only one dosage level so it is difficult to be precise about actual needs even in these trials. Thus, there is much less precision about the daily intake of a nutrient required to ‘prevent’ the chronic disease. Lowering of risk for these diseases is also often related to several nutrients, some of which appear to increase risk whilst others decrease it. For chronic disease, there may also be other influences on outcome such as genetic background and other environmental factors that are not always taken into account sufficiently.
For this reason it seemed more reasonable to provide separate recommendations for prevention of deficiency states and for prevention of chronic disease although both need to be taken into consideration when developing the Food and Nutrition Guidelines for healthy New Zealanders.
5. Why are there two sorts of recommendations for chronic disease?
There are two types of recommendations for chronic disease. One set address the balance of protein, fat and carbohydrate in the diet in terms of their relative contribution to dietary energy. These are the Acceptable Macronutrient Distribution Ranges (AMDR) and as the title suggests recommend a range of intake for a particular macronutrient that is consistent with good health (eg, protein from 15-25% of energy in the diet). The other set addresses specific nutrients such as antioxidants, dietary fibre or long chain omega-3 fats for which there is some evidence of benefit for chronic disease prevention at higher than RDI levels. These are generally set at the 90th percentile of current population intake as being a level likely to bring benefit without long-term risk. The recommendations for reducing risk of chronic disease are based on eating foods and the same benefits cannot be achieved by consuming dietary supplements.
6. How should the energy tables be used to determine energy needs for a particular person?
The energy tables give recommendations for energy intake for maintenance of body weight across a range of ages, gender and body size. They also show the requirements within these groups for different physical activity levels (PALs) as activity affects energy needs.
It is generally accepted that a PAL above 1.75 is consistent with good health but many people will have physical activity levels below this. The tables can thus be used to indicate what energy needs for a particular person should be if they were doing adequate physical activity and what energy level they will need to restrict themselves to in order to prevent weight gain, if doing inadequate physical activity.
7. Are there other factors such as nutrition interactions, medication and physical activity that may help or hinder achieving these recommendations?
There are a number of nutrients that can interact with other nutrients in a positive or negative way. For example, very high intakes of one nutrient such as iron may interfere with the absorption of another nutrient such as zinc which uses the same absorption mechanism. This is one of the potential problems with supplement use. Others nutrients such as vitamin C can help in the absorption of nutrients such as iron if consumed at the same time, eg, a glass of orange juice with baked beans. Some of these interactions have been taken into account in setting Upper Levels of Intake, others are better addressed when discussing food intake patterns in Food and Nutrition Guidelines. Some medications can affect the body’s ability to absorb and use nutrients, so advice should be sought especially with multiple medications. Physical activity levels can affect the requirements for a number of nutrients involved in energy metabolism such as certain B vitamins (and of course energy) but increased physical activity allows for greater food intake making it easier to attain all the required nutrients.
8. What does the term ‘equivalent ' mean (eg Dietary Folate Equivalents)?
For some of the nutrients the term ‘equivalent’ has been used to express the recommendations (eg, Vitamin A is expressed in Retinol Equivalents, folate in Dietary Folate Equivalents; vitamin E in alpha-tocopherol equivalent).This reflects the fact that for some nutrients there is more than one chemical form in the food supply that provide a benefit. For example, for folate, there is naturally occurring food folate as well as folic acid used for food fortification. Folic acid is twice as active as food folate so not as much is needed to get the same biological benefit. The overall requirement may be met by a mixture of these so is expressed as dietary folate equivalents.
9. How do these recommendations relate to the Ministry’s Food and Nutrition Guidelines?
These nutrient requirement recommendations form the basis of the Food and Nutrition Guidelines which are qualitative guidelines about the types and amounts of foods required to get the required nutrients. These new nutrient recommendations will be included in all future revisions of the Ministry’s Food and Nutrition Guidelines and nutrition policy documents.
10. When will these recommendations be reviewed again?
In line with current NHMRC policy, the recommendations will be reviewed five years from their publication.