| Please note: This document references the Food Guide Pyramid, which was updated in April 2005 by the United States Department of Agriculture and is now the MyPyramid Food Guidance System. Please check back for an updated version of this document. In the meantime, visit http://www.mypyramid.gov for more information. |
In 1997, the Food and Nutrition Board of the National Academy of Sciences did something dramatic: they changed the way nutritionists and nutrition scientists evaluate the diets of healthy people with the creation of the Dietary Reference Intakes (DRIs). Remember the Recommended Dietary Allowances (RDAs)? From 1941 until 1989, the RDAs were established and used to evaluate and plan menus that would meet the nutrient requirements of groups as well as other applications such as interpreting food consumption records of populations, establishing standards for food assistance programs, establishing guidelines for nutrition labeling, to name a few. Their primary goal was to prevent diseases caused by nutrient deficiencies. Technically speaking, the RDAs were not intended to evaluate the diets of individuals, but they were often used this way.
In the early 1990s, the Food and Nutrition Board, after much consideration, undertook the task of revising the RDAs and a new family of nutrient reference values was born—the Dietary Reference Intakes (DRIs). There are four types of DRI reference values: the Estimated Average Requirement (EAR), the Recommended Dietary Allowance (RDA), the Adequate Intake (AI) and the Tolerable Upper Intake Level (UL). (See Box for definitions of these values). The primary goal of having new dietary reference values was to not only prevent nutrient deficiencies, but also reduce the risk of chronic diseases such as osteoporosis, cancer, and cardiovascular disease.
Upcoming DRI Reports
Between 1941 and 1989, all of the RDA values were reviewed and published eleven times. Unlike past editions of the RDAs, the new DRI values have been released in stages. The first report,
Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and Fluoride, was published in 1997. Since then, three additional reports have been released which address folate and other B vitamins, dietary antioxidants (vitamins C, E, selenium and the carotenoids), and the micronutrients (vitamins A, K, and trace elements such as iron, iodine, etc). The next report, scheduled for publication in summer of 2002, will address macronutrients such as dietary fat and fatty acids, protein and amino acids, carbohydrates, sugars, and dietary fiber, as well as energy intake and expenditure.
Three additional nutrient reference reports are planned for this initial update: electrolytes and water (currently in development), bioactive compounds such as phytoestrogens and phytochemicals, and the role of alcohol in health and disease.
DRIs: For Professionals Only?
Chances are good that if consumers were asked whether they have ever heard of a dietary reference intake or DRI, they would answer with blank stares. In fact, focus group research with registered dietitians has indicated that health professionals also have many questions about how to use the DRI values.
For the most part, DRI values have been used by scientists and nutritionists who work in research or academic settings. Nutritionists who work primarily with consumers have not yet had to develop a detailed understanding of the DRIs. Nutritionists who develop menus that must meet certain nutritional requirements (elderly feeding programs, prison menus, military feeding programs) have had to become more familiar with the DRIs.
A lack of understanding among nutrition professionals about DRIs is not surprising to Jeanne Goldberg, PhD, professor at the Tufts University School of Nutrition, an expert in communicating nutrition science to the public. “The reports are much more comprehensive than ever before. Some of the confusion that people have may be because the reports have been released in stages. Also, the DRI reports are far more complicated documents to interpret to the public and to patients…remembering all the parameters such as the difference between an AI, EAR and an RDA is challenging. The DRIs are primarily for nutrition scientists, not for consumers,” explains Goldberg.
Nancy Clark, MS, RD, who advises both casual exercisers and elite athletes about nutrition in the Boston area, echoes the results of focus group research conducted in 1999 by the Food and Nutrition Board concerning the ability to understand the new DRIs. Clark readily admits that the DRIs are not something she has had to focus on in her work. Clark’s clients, who tend to be fairly savvy about nutrition, are not really tuned into the DRIs either. She states, “The DRIs, like many nutrition issues, have to be translated for consumers. People eat food, not nutrients. I’m encouraging people to eat fruits and vegetables rather than tell them to be sure to get enough vitamin C.”
“Communicating the DRIs to the nutrition community will take time,” says Allison Yates, PhD, RD, and director of the Food and Nutrition Board (FNB) which is responsible for coordinating the committees that have developed the DRI reports. Over the past 7 years Yates and her co-workers have been steadily working to help the nutrition community understand the significance of the new values and how to use them appropriately. The FNB has overseen the creation of several research articles published in scientific journals and other documents to help practitioners better understand the DRIs (see For More Information). In 2000, the FNB published
Dietary Reference Intakes: Applications in Dietary Assessment. A companion report,
Dietary Reference Intakes: Applications in Dietary Planning is expected to be released in Summer 2002. In addition, work is now underway on a guide that will summarize all of the DRI reports into one condensed, 300-page book. Yates expects the condensed version of the DRI reports to be available in August of 2002. Like the 1989 edition of the RDAs, the abbreviated version will contain highlights of all the reports, and the DRI values will be presented on foldout pages that can be easily referenced.
The DRIs: A Learning Process
Even with all the guidance and articles that the Food and Nutrition Board has published, Yates is still concerned about how the DRI values are being used. “Some people are still using two-thirds of the new RDA value to assess the nutrient intake of groups and this is not correct.” In the past, some practitioners who planned meals for groups would use two-thirds of the RDA value as an intake goal to prevent excess nutrient intake.
One of the major differences between the recent DRI reports and the previous RDAs is the creation of tolerable upper intake levels or ULs. The 1989 edition of the RDAs discussed “excessive intakes and toxicity.” ULs are different, however, and there have been misinterpretations of their meaning. According to Yates, “Above the UL there is
potential for increased risk, but there is an uncertainty factor which functions as a margin for safety compared to levels which have been shown to result in adverse effects. Consistently consuming a nutrient at the upper level should not cause adverse effects. Intake levels at the UL can be interpreted as a ‘warning flag,’ not as reason for alarm,” explains Yates. Yates also stresses, “It’s important to know how the UL was derived because there are not many studies that have been done on adverse effects of nutrient intake. For example, in the case of arsenic, we know it’s toxic but there is no UL because we don’t have enough data on chronic intake of lower doses to set a UL. When a UL cannot be determined, it is important to be careful about consuming levels above the RDA or AI.”
While many nutritionists have applauded the development of ULs, they do present communication challenges. Jeanne Goldberg stressed this challenge when she stated, “One of the real strengths of the DRI process was that they do address upper safe limits. But it is tough because they need to be communicated in broad strokes: they are not toxic levels.”
DRIs: Implications for Nutrition Policy
In the future, DRIs may impact food and nutrition policy such as food labeling, the Dietary Guidelines and the Food Guide Pyramid. But it will take time. Currently, a committee of the Food and Nutrition Board is studying how best to represent DRI values on a food label. A report on use of DRIs in nutrition labeling is expected in the Fall of 2003. One of the issues they are considering is whether it makes sense to follow previous guidelines which used the highest nutrient level for adolescents or adults as the daily value when that level may exceed the UL for children. Once the labeling report has been published, the Food and Drug Administration (FDA) may choose to propose changes to current food labeling laws.
Dietary Reference Intakes Reports Timeline
- 1997: Calcium and related nutrients (Phosphorous, Magnesium, Vitamin D, Fluoride)
- 1998: Folate and other B Vitamins, including Choline
- 2000: Vitamin C, Vitamin E, Selenium, and Carotenoids (Antioxidant Report)
- 2000: Dietary Reference Intakes: Applications in Dietary Assessment
- 2001: Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (Micronutrients)
- Summer 2002: Macronutrients (dietary fat, individual fatty acids [omega-3 and omega-6, trans fatty acids], protein, amino acids, cholesterol, carbohydrates, simple sugars, dietary fiber, energy intake, and energy expenditure)
- 2003: Electrolytes (sodium, potassium, chloride, and sulfate) and water
- 2005: Bioactive compounds, e.g., phytoestrogens and other phytochemicals, carnitine
- 2005: Role of alcohol in health and disease
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Dietary Reference Intakes Definitions
Recommended Dietary Allowance (RDA): the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular life stage and gender group.
Adequate Intake (AI): a recommended intake value based on observed or experimentally determined approximations or estimates of nutrient intake by a group (or groups) of healthy people, that are assumed to be adequate—used when an RDA cannot be determined.
Tolerable Upper Intake Level (UL): the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As intake increase above the UL, the potential risk of adverse effects increases.
Estimated Average Requirement (EAR): a daily nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a life stage and gender group—used to assess dietary adequacy and as the basis for the RDA.
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Comparison of 1989 RDA and DRI Values for Selected Nutrients. (Note: values in bold-faced type are previous or current RDA values. Values in plain type with an * indicate AI values.)
| 1989 RDA Ages 19-50 Years | New RDA or AI* Ages 19-50 Years | UL~ 19-70 Years |
| Women | Men | Women | Men | Men & Women |
| Vitamin A (μg/d)1 | 800 | 1,000 | 700 | 900 | 3,000 |
| Vitamin C (mg/d) | 60 | 60 | 75 | 90 | 2,000 |
| Vitamin D (μg/d) | 5-102 | 5-102 | 5* | 5* | 50 |
| Vitamin E (mg/d)3 | 8 | 10 | 15 | 15 | 1,0004 |
| Vitamin K (μg/d) | 60-655 | 70-805 | 90* | 120* | ND6 |
| Thiamin (mg/d) | 1.1 | 1.5 | 1.1 | 1.2 | ND |
| Riboflavin (mg/d) | 1.3 | 1.7 | 1.1 | 1.3 | ND |
| Niacin (mg/d)7 | 15 | 19 | 14 | 16 | 359 |
| B6 (mg/d) | 1.6 | 2.0 | 1.3* | 1.3* | 100 |
| Folate (μg/d)8 | 180 | 200 | 400 | 400 | 1,0009 |
| B12 (μg/d) | 2.0 | 2.0 | 2.4* | 2.4* | ND |
| Calcium (mg/d) | 800-1,200 | 800-1,20010 | 1,000* | 1,000* | 2,500 |
| Iron (mg/d) | 15 | 10 | 18 | 8 | 45 |
| Zinc (mg/d) | 12 | 15 | 8 | 11 | 40 |
*AI: Adequate intakes are estimated when an RDA cannot be determined.
UL: The maximum level of daily nutrient intake that is likely to pose no risk of adverse affects.
Provitamin A carotenoids in the 1989 RDA were 1 μg vitamin A = 1 μg RE = 6 μg β-carotene = 12 μg α-carotene and β-cryptoxanthin. Provitamin A carotenoids in the 2001 DRI were 1 μg vitamin A =1μg RE = 12 μg β-carotene = 24 μg α-carotene and β-cryptoxanthin.
For both men and women, the 1989 RDA for vitamin D was 10 μg/d for 19-24 year olds and 5 μg/d for 25 to 50 year olds.
As α-tocopherol only.
ULs for vitamin E include all forms of supplementary α-tocopherol.
For vitamin K, the 1989 RDA for 19-24 y.o. women and men was 60 & 70 μg/d, respectively; for 25-50 y.o. women and men; it was 65 & 80 μg/d, respectively.
ND: not determined. When a UL cannot be determined, extra caution may be warranted in consuming levels above the recommended intakes.
As niacin equivalents (NE). 1 mg of niacin = 60 mg tryptophan.
As dietary folate equivalents (DFE). 1 DFE = 1 μg food folate = 0.6 μg of folate from fortified food or as a supplement consumed with food = 0.5 μg of a supplement taken on an empty stomach.
ULs for folate and niacin refer to forms supplied by supplements, fortified foods, or a combination of the two.
For calcium, the 1989 RDA was 1,200 mg/day for 19-24 y.o. men and women and 800 mg/d for 25-50 y.o. men and women.
For More Information or Additional Reading. . .
- http://www.iom.edu: Under Institute of Medicine Programs, go to the Food and Nutrition Board. Check the status of DRI reports, download DRI tables, read DRI reports on line, or order publications.
- “Nutrient Requirements Get a Makeover: The Evolution of the Recommended Dietary Allowances.” Food Insight, September/October 1998.
- Journal Articles
- Yates, AA, Schlicker, SA, and Suitor, CW. Dietary Reference Intakes: The new basis for recommendations for calcium and related nutrients, B vitamins and choline. J Am Diet Assoc 1998; 98:699-706.
- Monsen, ER. Dietary Reference Intakes for antioxidant nutrients: Vitamin C, vitamin E, selenium, and carotenoids. J Am Diet Assoc 2000; 100:637-640.
- Trumbo, P, Yates, AA, Schlicker, SA, and Poos, MI. Dietary Reference Intakes: Vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. J Am Diet Assoc 2001; 101: 294-301.
- Barr, S.I., Murphy, S.P., and Poos, M.I., Interpreting and using the Dietary Reference Intakes in dietary assessment of individuals and groups. J. Am. Diet. Assoc., 2002;102: (6).
