As essential nutrients, sodium and potassium contribute to the fundamental physiology of human health. In the clinical setting, these are frequently measured blood electrolytes. Yet, blood electrolyte concentrations are rarely influenced by typical dietary intake in healthy individuals, as the kidney and hormone systems carefully regulate blood values. However, the sodium and potassium intake story is more dynamic in the public health setting. Evidence suggests that sodium and potassium intakes influence current and longer-term population health in children and adults mostly through complex and not fully understood mechanisms between dietary intake and blood pressure and cardiovascular health status. Based on a 2017 report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, 50 percent of men and 44 percent of women ages 45–54 years have clinically significant hypertension, and the prevalence increases with age. This information—such high prevalence of hypertension beginning early in adult life—was a surprise to me. Cardiovascular disease, including diagnoses of cardiovascular disease risk factors such as prehypertension, hypertension, and abnormal blood lipids, is common, and a majority of adults in the United States has more than one cardiovascular disease risk factor. The public health importance of the relationships of sodium and potassium intakes and health is clear. Congress asked the Centers for Disease Control and Prevention (CDC) to undertake a review of the Dietary Reference Intakes (DRIs) for sodium. Given the interrelationship between sodium and potassium, it was determined that assessing both together would be prudent. CDC, together with the Food and Drug Administration, Health Canada, the National Institutes of Health, the Public Health Agency of Canada, and the U.S. Department of Agriculture, sponsored this study. The National Academy of Sciences' W.K. Kellogg Foundation Fund and the National Academy of Medicine's Kellogg Health of the Public Fund provided additional financial support.

The committee was charged to review the available evidence and to update the current DRIs for sodium and potassium. In 2005, the evidence supported an Adequate Intake (AI) for both nutrients, and a Tolerable Upper Intake Level (UL) only for sodium. In addition, we were asked to consider adding, if relevant, sodium and potassium intake values to reduce the risk of chronic disease endpoints. Committee deliberations were guided by three sources: Effects of Dietary Sodium and Potassium Intake on Chronic Disease Outcomes and Related Risk Factors, an Agency for Healthcare Research and Quality (AHRQ) systematic review of the evidence commissioned to be used by this committee; Guiding Principles for Developing Dietary Reference Intakes Based on Chronic Disease; and the DRI organizing framework. The 2011 Dietary Reference Intakes for Calcium and Vitamin D also served as a resource, as it was the most recent DRI report that considered the evidence of dietary intake and chronic disease indicators to make recommendations.

In addition to these reports, the committee gained insight from expert testimony, additional comprehensive literature searches as needed to ascertain the state of the science on specific questions, and committee expertise and deliberation. Our committee members represented key disciplines and skill sets needed for this work; they not only dedicated significant time and effort, but also created a collaborative environment of learning, lively debate, and commitment to a thorough review prior to making decisions. Implementing the new DRI concept of dietary intake recommendations of reduce the risk of chronic disease was a responsibility the committee embraced. This report provides the first DRI based on chronic disease recommendations and documents both the evidence and the deliberative process to inform future DRI committees considering chronic disease recommendations.

Research into cardiovascular disease, hypertension, and diet has been among the priority areas for decades, yet numerous knowledge gaps persist. Additional research is essential to inform the next review of how sodium and potassium dietary intakes affect health across the DRI life stages. High-quality evidence to guide dietary recommendations to support the health of the youngest children, oldest adults, and pregnant and lactating women in the United States and Canada is also sparse.

Understanding the food and beverage sources of dietary sodium and potassium was not examined in detail, nor were the complex interactions of nonprocessed and processed food availability, cultural and personal taste preference, and behavioral components of food choice. However, some common misconceptions came to light. Most of the salt in our modern diet pattern comes from commercially prepared food and beverage components and products, not from salt added by consumers cooking at home or from salt added by the consumer at the time of consumption. When considering sodium sources for the population over 2 years of age, most common sodium sources are breads, pizza, and cured meats and poultry. For children specifically, cheese is the top food category source of sodium, followed by cured meats and poultry, and then mixed dishes including pizza. For the desired public health benefit of reduced sodium intake to be achieved, more attention must be paid by industry to reducing sodium in the food supply and by consumers who have the needed sodium content information and an understanding of how to make health-inspired food choices. Dietary potassium intake is related to specific vegetable or fruit intakes—and then remember that as a population, our vegetable and fruit intake rarely meets the recommended servings per day. When you consider all ages, higher dietary sources of potassium are from milk, white potatoes, and fruit. Coffee is the top source of potassium in people in the 51 years of age and older group in the United States.

The committee thoroughly considered the totality of evidence available and used processes now established for DRI review and revisions. Our DRI report provides a sodium intake level as an AI, and with sodium, the report establishes the first Chronic Disease Risk Reduction Intake (CDRR) level. Our report provides a potassium intake level as an AI, and the committee determined there was insufficient evidence to establish a CDRR for potassium. In addition, using the evolving toxicological risk assessment approach, the committee found there was insufficient evidence of risk of excess sodium or potassium intake within the healthy populations to establish a UL for either nutrient.

Many other people contributed to this report. Two consultants, Mei Chung and Paul Whelton, provided their advice and guidance to the committee. Emily Callahan provided editorial assistance with the report. The National Academies Research Center, particularly Jorge Mendoza-Torres, provided support and assistance with the design and execution of the committee's scoping literature searches. The committee was also assisted by Jennifer Garner, who was an intern with the Food and Nutrition Board in Spring 2018. The committee would also like to thank both CDC and Health Canada for providing intake distribution tables and other information requested by the committee.

Lastly, as chair, I express my sincere appreciation to each committee member and to each member of our National Academies staff, including Meghan Harrison and Maria Oria, for their extraordinary commitment to the project and to our shared goal to complete this complex task in a way that serves the public's health and health care in general. We worked well together to prepare a report that will contribute to actively improving the health of children and adults.

Virginia A. Stallings, Chair

Committee to Review the Dietary Reference Intakes for Sodium and Potassium