How much is enough, too much, or not enough?
Dietitian Jeni Pearce, with the expert advice of Elizabeth Aitken and Eirean Kiely, Ministry of Health, explains recent changes to the recommended amounts of nutrients we should be having according to the Ministry of Health.
In May 2006, new Nutrient Reference Values (NRVs), which include recommendations for intakes of essential nutrients for NZers and Australians, were released in both countries. Experts from both countries reviewed the latest scientific advice and knowledge from around the world in the preparation of this, the first major review of the nutrient recommendations in NZ and Australia in 15 years. The new NRVs are more comprehensive than the previous values.
Why have the NRVs been produced?
The NRVs are key tools for specialist nutrition experts such as dietitians, hospital and medical specialists, researchers, universities and Government agencies. Examples of their uses include: identifying the level of inadequate intakes in the general population or in specific conditions, including assessing national nutrition surveys; developing and evaluating menus (in schools, hostels, hospitals etc); developing food and nutrition guidelines for healthy NZers; for food legislation; and as guidelines for food manufacturers.
Different NRVs have been developed to be used in a range of situations, such as to prevent dietary deficiencies, to set safe upper intake levels, and to reduce the risk of chronic disease.
What is an RDI?
Many people assume the Recommended Dietary Intake (RDI) is the minimum amount of a nutrient a person should consume. In fact, the RDIs are set at a level that meets the needs of 97-98% of healthy NZers at different life stages. While the RDI (or Adequate Intake (AI) where there is no RDI) is a useful goal for people, it is recognised that on some days, intakes of particular nutrients may be over or under the RDI. Failure to meet the RDIs from time to time will not cause a deficiency and does not necessarily mean that supplements are required. RDIs do not cover those who are ill or have special dietary requirements.
Can I have too much of a nutrient?
Yes. With some nutrients, an Upper Level of Intake (UL) is set where it's known high intakes can be harmful to health. Some nutrients which we cannot live without, but can be a risk to health at high intakes on a daily basis include vitamin A, vitamin D, iron and selenium. So it's important to remember that while we need these nutrients, more is not always better.
What's new in the NRVs?
The main changes in the new recommendations are:
- More information: More nutrients (36 in total) are covered and there is more detail on energy requirements. The range of recommendations, collectively known as NRVs, now include not just the RDI but also three other related values (AI, EAR, UL – see table below).
- New nutrients: New nutrients are now included due to new scientific research about their role in health and disease prevention. These include omega-3 fats, omega-6 fats, vitamin K, water, fluoride, chromium, manganese and molybdenum.
- Macronutrients: In addition to the NRVs, information is given on Acceptable Macronutrient Distribution Ranges (AMDRs). These are the estimated ranges for intakes of the macronutrients; protein, carbohydrates and fat, which also allow for an adequate intake of all other nutrients and to maximise health.
The NRVs provide a basis for the Ministry of Health's food and nutrition guidelines for healthy NZers. These guidelines translate the NRVs into food and lifestyle patterns for NZers to follow.
- Chronic disease: For the first time there is advice about the type of dietary pattern and key foods people should eat to reduce the risk of chronic disease, such as heart disease, high blood pressure and some cancers. This advice, based on research studies, includes Suggested Dietary Targets (SDTs) for selected vitamins and minerals that we need to consume in greater amounts to help prevent chronic diseases. These higher intakes of selected nutrients must come from foods, as the same health benefits cannot be achieved by taking supplements. To meet these targets we should be eating more whole grains (especially whole grain bread and cereals), vegetables and fruit, and oily fish. The advice to eat at least five servings a day of vegetables and fruit may not be enough to achieve some of these nutrient intakes and seven or more servings of vegetables and fruit may be needed.
- Salt: One of the most dramatic changes is the sodium (salt) recommendation. This has been decreased to around half of the previous recommendations. The new recommendation is similar to half a teaspoon of salt. This reduced intake can be achieved by eating more fresh food, especially vegetables and fruit, using few processed foods with added salt, not adding salt to food or eating high-salt foods regularly. This change may encourage food manufacturers to reduce the amount of sodium added to foods, particularly foods eaten daily such as bread, crackers and prepared cereals.
- Calcium: Calcium levels have increased for everyone, most noticeably for teenagers, older men (over 70 years) and women (after menopause). The recommended intake was 800mg for men and 1000mg for older women and it is now 1000-1300mg. This equals a daily intake of at least three to four servings of calcium-rich dairy foods or other calcium-rich foods (fish with bones, such as canned salmon or fortified soy products). As many foods are now fortified with calcium (milk, juices, biscuits, some breads and breakfast cereals) these higher intakes are achievable.
- Vitamin D: Previously there was no RDI for vitamin D as the assumption was made that sufficient amounts were provided through skin exposure to sunlight and that our climate provided plenty of sunshine hours. However, with the increasing diversity within our population and new research, this assumption may no longer be correct. People who may not be getting enough vitamin D include: people with darker skin; those covering up to reduce the risk of skin cancer or for other reasons (women and girls in veils); people who stay inside more often (e.g. immobile older people); and those living in the South Island during winter (lower sunlight hours). Adequate vitamin D is important for calcium uptake by bones to make them strong and reduce the risk of bone thinning and weakness (osteoporosis). In addition to having an AI, Vitamin D now has a UL as high intakes are potentially harmful.
- B vitamins: The RDIs for many of the B group vitamins (thiamin, niacin, folate, vitamin B6 and B12) have also risen. Folate is a B group vitamin that is essential for healthy cells, used by the body in the metabolism of alcohol, and that has a preventative role for neural tube defects, which can affect the unborn baby during pregnancy. Folate may have a protective role in reducing risk of chronic diseases, such as heart disease and some forms of cancer. The different forms of folate have also been quantified; folic acid, the form in fortified foods and supplements, is known to be much more readily absorbed and active than the folates in food. Now that we know so much more about folate, its RDI has substantially increased.
- Energy and physical activity: In-depth information on the estimation of energy requirements for all age groups is now provided, including different energy requirements for different lifestyles and activity levels. These differences in energy needs are described as physical activity levels (PALs) which range from bed rest (PAL=1.2) to vigorous or very active (PAL=2.2). A PAL of at least 1.75, which is moderate activity (30 minutes of moderate-intensity activity most days, e.g. brisk walking, cycling, stair climbing) for adults is required to maintain good health.
How do we achieve our daily RDI?
Overall, most of us can easily meet the recommended intake of nutrients by increasing our intake of vegetables, fruit and whole grains every day. Support this by eating low-fat dairy foods for calcium, lean protein servings (such as lean meat, chicken, fish, eggs, legumes and pulses) and small amounts of oils from plants and seeds. Doing this should help you achieve the new recommended levels without the need for supplements.
For more information about the new NRVs, contact a dietitian. Copies of the NRVs are available from the Ministry of Health or hard copies of the two documents can be ordered from Wickliffe Ltd, PO Box 932, Dunedin or email: [email protected]
What are the new terms and definitions? Some new terms have been introduced because there are a number of recommended intake levels for each nutrient. Previously, the one level of recommendation used was called the RDI. The NRV terms and definitions are as follows: RDI: Recommended Dietary Intake The average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97–98%) healthy individuals in a particular life stage and gender group. AI: Adequate Intake (used when an RDI cannot be determined) The average daily nutrient intake level based on observed or experimentally-determined approximations or estimates of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate. UL: Upper Level of Intake The highest average daily nutrient intake level likely to pose no adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse affects increases. EER: Estimated Energy Requirement The average dietary energy intake that is predicted to maintain energy balance in a healthy adult of defined age, gender, weight, height and level of physical activity, consistent with good health. In children and pregnant and lactating women, the EER is taken to include the needs associated with the deposition of tissues or the secretion of milk at rates consistent with good health. AMDR: Acceptable Macronutrient Distribution Range The AMDR is an estimate of the range of intake for each macronutrient for individuals (expressed as percent contribution to energy), which would allow for an adequate intake of all the other nutrients whilst maximising general health outcome. SDT: Suggested Dietary Target A daily average intake from food and beverages for certain nutrients that may help in prevention of chronic disease. *Adapted from the Food and Nutrition Board: Institute of Medicine Dietary Reference Intakes.