Dietary Reference Intakes (DRI): An Overview

How do we know how much of a given nutrient people should eat—or how much is too much? To answer these questions, nutrition scientists rely on the Dietary Reference Intakes (DRIs). The DRIs are a set of science-based recommendations developed by the National Academies of Sciences, Engineering, and Medicine to describe the amounts of specific nutrients and energy that people should consume to maintain health.

The DRIs are established by expert panels of nutrition scientists who carefully evaluate the available research. Their goal is to determine how much of a nutrient is needed to prevent deficiency and reduce the risk of chronic disease, as well as the intake level at which a nutrient may become excessive and potentially toxic.

These recommendations apply specifically to generally healthy individuals living in the United States and Canada. People with certain medical conditions, life circumstances, or unique metabolic needs may require nutrient intakes that differ from DRI values.

Categories of Dietary Reference Intakes (DRI)

The DRIs fall into two broad categories:

• DRIs for energy intake
  Recommendations for total calorie needs and the proportion of energy supplied by carbohydrate, fat, and protein

• DRIs for nutrient intake
  Recommendations for vitamins, minerals, and other nutrients, including upper intake levels where excess may pose health risks

In the sections that follow, each category will be examined in detail, along with how DRI values are applied in nutrition research, public health policy, and dietary planning. Along the way, you will encounter many commonly used nutrition acronyms.

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DRI for Energy Intake

The DRIs include recommendations for energy intake that address the number of calories needed to support normal body functions, physical activity, growth, and reproduction. There are two DRI values related to energy; the first is described below.

Estimated Energy Requirement (EER)

The Estimated Energy Requirement (EER) is the average number of calories a person needs to consume each day to maintain health. It is calculated using age, sex, height, weight, and physical activity level.

• For adults, the EER represents the energy intake level that maintains energy balance, meaning it should not result in weight gain or weight loss over time.

• For children and adolescents, the EER includes energy needed for normal growth and development.

• For pregnant and lactating women, the EER accounts for the additional energy required to support fetal development, pregnancy-related physiological changes, or milk production during lactation.

Because energy expenditure increases with physical activity, separate EER values are provided for different activity levels. More physically active individuals require more energy than sedentary individuals.

The EER should be viewed as a general estimate rather than a precise prescription. As will be discussed throughout this book, individual energy needs can vary substantially. Two people with the same sex, height, weight, and physical activity level may still have different calorie requirements due to differences in metabolism, body composition, and other physiological factors.

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Acceptable Macronutrient Distribution Ranges (AMDR)

The AMDR specify the recommended percentage of total daily calories that should come from carbohydrate, fat, and protein to support overall health and reduce chronic disease risk. These values are population-based guidelines rather than exact individual requirements.

Because carbohydrates, fats, and proteins together provide 100 percent of daily energy, increasing one macronutrient necessarily decreases the others. Diets that consistently fall outside the AMDR—such as very low-carbohydrate patterns—may increase health risks by displacing other essential macronutrients. The AMDRs are intentionally broad, allowing many dietary patterns to fit within them.

 

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DRI for Nutrients: EAR, RDA, AI, and UL

There are four different types of DRI values used to describe recommendations for the intake of individual nutrients:

• Estimated Average Requirements (EAR)
• Recommended Dietary Allowances (RDA)
• Adequate Intakes (AI)
• Tolerable Upper Intake Levels (UL)

DRI values are summarized in tables to make it easy to find a specific value for a person based on their life stage and sex. For example, part of a table of EAR values for macronutrients and vitamins is shown below in Figure 2.12.

The data in the above table is from National Institutes of Health Office of Dietary Supplements, which provides links to DRI reports and tables: Nutrient Recommendations: Dietary Reference Intakes (DRI)

Let’s look at how each of these DRI values is determined, what they mean, and how they are used.

Estimated Average Requirement (EAR)

The Estimated Average Requirement (EAR) is the amount of a nutrient that meets the requirements of 50% of healthy people in a specific life-stage and sex group. Because individual nutrient needs vary, some people require less than the EAR, while others require more. The EAR represents the midpoint of this range of individual requirements.

To set an EAR, scientists review research on a nutrient and select a measurable biological function to serve as the benchmark. For example, the EAR for calcium is based on the intake needed to support bone health, a key and measurable function of calcium.

If everyone consumed only the EAR, about half of the population would not meet their needs. For this reason, the EAR is not intended as an intake goal for individuals. Instead, it is used primarily to calculate the Recommended Dietary Allowance (RDA), which is designed to meet the needs of nearly all healthy people.

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Recommended Daily Allowances (RDA)

Once the Estimated Average Requirement (EAR) has been established, the Recommended Dietary Allowance (RDA) can be calculated. While the EAR meets the needs of 50 percent of a healthy population, the RDA is set to meet the needs of 97–98 percent of people in the same life-stage and sex group. Because of this, the RDA is the preferred intake target for populations and individuals.

It is important to understand that the RDA is not the same as an individual requirement. For example, consuming less than the RDA for calcium does not automatically mean a person is deficient or will develop osteoporosis—an individual’s true requirement may be lower than the RDA. However, because most people do not know their exact nutrient needs, the RDA serves as a practical and protective target. The further intake falls below the RDA, the greater the risk of inadequacy over time.

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Comparing the RDA and the EER

It’s interesting to compare and contrast the EER (for energy or calorie intake) and the RDA (for nutrient intake).

• EER (energy): Designed to meet the average calorie needs of an individual to maintain body weight

• RDA (nutrients): Designed to meet the needs of nearly all healthy people

If the EER were set like the RDA—to meet the needs of almost everyone—it would greatly overestimate calorie needs for most people and lead to weight gain. This approach works for nutrients because the body can store, metabolize, or excrete excess amounts of many nutrients, making modest intakes above requirements generally safe.

Adequate Intake (AI)

When there is not enough scientific evidence to establish an Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) for a nutrient, the National Academies may set an Adequate Intake (AI) instead. The AI is based on observed intakes of healthy people and represents a best estimate of the amount needed to maintain nutritional adequacy. Although less precise than an RDA, the AI serves as the intake goal when no RDA is available.

A common example is infancy. Because it is difficult to determine exact nutrient requirements for infants, all DRI values for this age group are based on AIs, which are derived from the nutrient composition of human breast milk. For older infants and young children, AI values are informed by breast milk data along with research from older age groups.

AI values are intended for healthy populations and may not be appropriate for individuals with special needs, such as premature infants or those with certain medical conditions.

Tolerable Upper Intake Levels (UL)

While consuming too little of a nutrient can lead to deficiency, consuming too much can also cause health problems. The Tolerable Upper Intake Level (UL) is the highest average daily intake of a nutrient unlikely to cause adverse health effects in healthy individuals.

It is uncommon to exceed the UL when following a balanced diet based on whole foods. However, excessive intakes may occur when using dietary supplements, consuming highly fortified foods (such as protein bars or energy drinks), or relying on a very limited variety of foods. For this reason, supplements should be chosen carefully and should not exceed the UL for any nutrient unless recommended by a physician or registered dietitian.

Not all nutrients have an established UL. When a UL has not been set, it does not mean that high intakes are necessarily safe—only that there is currently insufficient evidence to determine a safe upper limit. Because nutrition science continues to evolve, caution is still warranted with high-dose nutrient intakes.

Comparing the DRI

The graph below summarizes the meaning of the 4 DRI values for nutrient intake.

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As nutrient intake increases from very low to very high, the risk to health changes. At low intakes, the risk of nutrient deficiency is high. As intake increases, this risk decreases. The Estimated Average Requirement (EAR) marks the intake level that meets the needs of 50 percent of the population, while the Recommended Dietary Allowance (RDA) meets the needs of 97–98 percent of healthy individuals.

The Adequate Intake (AI) represents an intake level known to support health when there is not enough evidence to set an EAR and RDA. It generally falls between the EAR and the Tolerable Upper Intake Level (UL). The UL is the highest intake that is unlikely to cause harm. Intakes above the UL increase the risk of adverse health effects.

There is typically a wide margin of safety between the RDA and the UL, meaning that exceeding the RDA does not usually cause toxicity. However, this margin varies by nutrient. Fat-soluble vitamins (A, D, E, and K) have a smaller safety margin than water-soluble vitamins, making excessive intakes more likely to cause toxicity.

How DRIs Are Used

Individuals can use the DRIs to help assess and plan their diets. Keep in mind that the values established have been set with a generous safety margin and should be used as guidance for optimal intakes. Also, the values are meant to assess and plan the average intake over time; that is, you don’t need to meet these recommendations every single day—meeting them over several days is sufficient.

The DRIs are also used by professionals, government agencies, and the food industry.  Below are some examples of their applications. ^[1]

• Health professionals. Registered dietitians and other nutrition professionals use the DRIs to provide dietary counseling and education and to plan menus for institutions, such as hospitals, long-term care, and prisons.
• Development of dietary guidelines. These include the U.S. Dietary Guidelines for Americans, MyPlate, and Canada’s Food Guide. In each case, developers ensure that their advice will help people meet the DRI standards.
• Nutrition labeling. The DRIs help inform Nutrition Facts labels on foods and Supplement Facts labels on supplement products.
• Assistance programs. School meals, WIC, SNAP, Child and Adult Care, and Administration on Aging programs must ensure that their programs align with the DRI.
• Nutrition monitoring research. Data from surveys of what people in the U.S. and Canada eat are compared with the DRIs to monitor national nutritional health.
• Military. The military uses the DRIs as a reference to ensure the armed forces’ nutrient needs are met, plan meals, and procure military rations.
• Food and supplement industries. In developing healthy food and safe supplement products, these industries should refer to the DRI.

attributions

This section is an adaptation of “Defining Nutrition Requirements” in Nutrition: Science and Everyday Application by Alice Callahan, PhD; Heather Leonard, MEd, RDN; and Tamberly Powell, MS, RDN under a Creative Commons Attribution-NonCommercial 4.0 International License.