In 1997, the Food and Nutrition Board of the National Academy of Sciences did something dramatic: it changed the way nutritionists and nutrition scientists evaluate the diets of healthy people by creating the Dietary Reference Intakes (DRIs). Remember the Recommended Dietary Allowances (RDAs)? From the time they were established in 1941, the RDAs were used to evaluate and plan menus that would meet the nutrient requirements of various groups as well as other applications such as interpreting food consumption records of populations, establishing standards for food assistance programs, and establishing guidelines for nutrition labeling, to name a few. Their primary goal was to prevent diseases caused by nutrient deficiencies. In technical terms, the RDAs were not intended to be used to evaluate the diets of individuals, but they were often used that way.
In the early 1990s, after much consideration, the Food and Nutrition Board undertook the task of revising the RDAs and a new family of nutrient reference values—the Dietary Reference Intakes (DRIs)—were born. 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 accompanying box for definitions of these values). The primary goal of having new dietary reference values not only was to prevent nutrient deficiencies, but also was to reduce the risk of chronic diseases such as osteoporosis, cancer, and cardiovascular 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 DRIs.
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 (child nutrition programs, elderly feeding programs, prison menus, military feeding programs) have had to become more familiar with the DRIs.
A lack of understanding of DRIs among nutrition professionals is not surprising to Jeanne Goldberg, Ph.D., a professor at the Tufts University School of Nutrition and 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, M.S., R.D., who advises both casual exercisers and elite athletes in the Boston area about nutrition, 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 also not really tuned into the DRIs. 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, Ph.D., R.D., 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 coworkers 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. In 2000, the Food and Nutrition Board 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. The DRIs will be presented on foldout pages that can be easily referred to for reference.
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, with intakes “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.”
Although 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 (DRIs) do address upper safe limits. But it is tough because they need to be communicated in broad strokes: they are not toxic levels.”
Definitions of Dietary Reference Intakes
Recommended Dietary Allowance (RDA): the average daily dietary intake that is sufficient to meet the nutrient requirement of nearly all (97 to 98 percent) healthy individuals in a particular group according to stage of life and gender.
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; AI is used when an RDA cannot be determined.
Tolerable Upper Intake Level (UL): the highest daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. As the intake increases 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 requirements of half of the healthy individuals in a group according to life stage and gender—used to assess dietary adequacy and as the basis for the RDA.
For More Information or Additional Reading...
- www.iom.edu: Under Institute of Medicine Programs, go to the Food and Nutrition Board to check the status of DRI reports.
- http://ific.org: “Nutrient Requirements Get a Makeover: The Evolution of the Recommended Dietary Allowances.” Food Insight, September/October 1998.
