Good nutrition is more than just preventing deficiencies and avoiding possible adverse effects from excessive intakes—good nutrition supports health. Knowing how much of a nutrient is needed, how those needs vary within and among different groups of people, and whether there may be risks from consuming too much or too little is critical information for nutrition programs, policies, planning, assessment, and regulatory initiatives. In the United States and Canada, estimates of these intake levels are established as Dietary Reference Intakes (DRIs).
The Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine has published standards for nutrient intakes since the 1940s. The standards began as a single category of intake levels estimated to meet the needs of nearly all healthy persons by age and sex. By the 1990s, the nutrition research landscape had dramatically changed. A new paradigm for establishing reference nutrient intakes was needed. What emerged were the DRIs. Drawing on advancements of scientific and statistical understandings, the DRIs featured four categories of reference intake values and are intended to help individuals optimize their health, prevent disease, and avoid consuming too much of a nutrient.
Estimate Average Requirement (EAR)
Average daily nutrient intake level estimated to meet the requirement of half the healthy individuals in a particular age, sex, and life-stage group
Recommended Dietary Allowance (RDA)
Average daily nutrient intake level sufficient to meet the nutrient requirement of nearly all (97-98%) healthy individuals in a particular age, sex, and life-stage group
Adequate Intake (AI)
An intake (not a requirement) that is likely to exceed the actual requirements of almost all individuals in an age, sex, and life-stage group; established when scientific evidence is not sufficient to determine an RDA
Tolerable Upper Intake Level (UL)
The highest average daily nutrient intake level likely to pose no risk of adverse health effects for nearly all people in a particular age, sex, and life-stage group
Although evidence on relationships between nutrient intakes and chronic disease risk had been included in DRI reviews for various nutrients, it was often difficult to use. Some of the challenges include:
To overcome these limitations, a new approach for using this type of evidence in the DRI process was developed. The evidence can now be used to establish a new DRI category called the Chronic Disease Risk Reduction Intake (CDRR).
Sodium and potassium are the first two nutrients reviewed under the expanded DRI model. This 2019 review updated the sodium and potassium DRI values published in 2005 under the original DRI model. Although each nutrient has unique considerations, changes reflected in the updated sodium and potassium DRI values serve as important illustrative examples of the evolving DRI model.
There is not yet enough evidence to determine when sodium needs are met using the criteria of the DRI model. More evidence on sodium requirements of healthy people is needed. The updated values remain AIs. An AI intake level is considered to be adequate for almost all people, but its exact relationship with actual requirements is unknown.
In the expanded DRI model, it’s recommended that ULs be based on adverse effects of excessive intakes that are not related to chronic disease risk, as those types of relationships are intended to be captured in the new DRI category, the CDRR. Although some studies reported non-chronic disease-related symptoms with higher or more concentrated sodium intakes, the evidence was too limited to establish a sodium UL based on this type of adverse effect.
Across the body of scientific studies, there was moderate strength of evidence that decreasing high sodium intakes reduces risk of cardiovascular disease and hypertension, and high strength of evidence that it lowers blood pressure. The sodium CDRR for adults was established as the lowest level of sodium intake for which there was moderate strength of evidence of chronic disease risk reduction.
There is not yet enough evidence to determine when potassium needs are met using the criteria of the DRI model. More evidence on potassium requirements of apparently healthy people is needed. The updated values remain AIs, although they are based on a different collection of evidence than the potassium AIs established in 2005. An AI intake level is considered to be adequate for almost all people, but its exact relationship with actual requirements is unknown.
Evidence was reviewed to find a measure, marker, or outcome that reflected potassium adverse effects or toxicity, separate from chronic disease, to establish a UL. No such indicator could be identified. As was the case in the 2005 report, potassium still does not have a UL. The lack of a potassium UL doesn’t mean that there is no risk from excessive intake. Caution against high intake through supplemental potassium is warranted for certain population groups, particularly those with or at high risk for compromised kidney function.
There’s evidence that potassium supplementation reduces blood pressure, particularly in adults with hypertension. However, across the studies, higher potassium intakes didn’t result in greater reductions in blood pressure—that is, an intake-response relationship could not be established. Evidence relating potassium intake to risk of chronic diseases, such as cardiovascular disease, was also limited. The evidence is not yet sufficient to establish a potassium CDRR. This doesn’t mean that increasing potassium intake may not reduce chronic disease risk. Rather, more evidence is needed in order to be able to characterize how chronic disease risk changes over a range of potassium intakes.