Scientific Report of the 2015 Dietary Guidelines Advisory Committee

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Part D. Chapter 6: Cross-Cutting Topics of Public Health Importance

Introduction

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The Dietary Guidelines for Americans, 2010 included guidance on sodium, saturated fat, and added sugars, and the 2015 DGAC determined that a reexamination of the evidence on these topics was necessary to evaluate whether revisions to the guidance were warranted. These topics were considered to be of public health importance because each has been associated with negative health outcomes when over-consumed. As the Committee considered it essential to address these topics across two or more Subcommittees, Working Groups were formed with representatives from the relevant Subcommittees to ensure that the topics were thoroughly addressed in a coordinated way. Additionally, the Committee acknowledged that a potential unintended consequence of a recommendation on added sugars might be that consumers and manufacturers replace added sugars with low-calorie sweeteners. As a result, the Committee also examined evidence on low-calorie sweeteners to inform statements on this topic. The updated findings in this chapter will help inform recommendations on these topics for the 2015 Dietary Guidelines for Americans.

Although sodium, saturated fat, and added sugars are receiving particular focus here, it is important to consider these aspects of the diet in the context of a healthy dietary pattern. A healthy dietary pattern has little room for sodium, saturated fat, and added sugars. That said, these components of the diet are modifiable, and strategies at various levels of the socio-ecologic model, ranging from policy to consumer education, can promote shifts in intake to support healthy dietary patterns.

The sodium, saturated fat, and added sugars sections of this chapter provide introductory text related to the topic including the rationale and approach for the Committee’s review. Because the questions within each topic are so complementary, the DGAC choose to develop only one implications section for each topic.

List of Questions

Sodium

  1. What is the relationship between sodium intake and blood pressure in adults?
  2. What is the relationship between sodium intake and blood pressure in children?
  3. What is the relationship between sodium intake and cardiovascular disease outcomes?
  4. What effect does the interrelationship of sodium and potassium have on blood pressure and cardiovascular disease outcomes?

Saturated Fat

  1. What is the relationship between intake of saturated fat and risk of cardiovascular disease?

Added Sugars and Low-Calorie Sweeteners

  1. What is the relationship between the intake of added sugars and cardiovascular disease, body weight/obesity, type 2 diabetes, and dental caries?
  2. What is the relationship between the intake of low-calorie sweeteners and body weight/obesity and type 2 diabetes?

Methodology

To answer the questions in this chapter, the Committee relied on existing reports, original Nutrition Evidence Library (NEL) systematic reviews, and NEL updates. The Committee followed the methods described in Part C. Methodology without modification to answer these questions. Because the DGAC knew strong existing reports, systematic reviews (SRs), and meta-analyses (MA) were available related to most of the cross-cutting questions, to prevent duplication of efforts, the DGAC relied on these reviews in lieu of conducting original NEL systematic reviews. In some cases, existing reviews, SRs, or MA were not available or required updating. In these cases, NEL systematic reviews or updates were conducted. Complete information on the NEL reviews and updates is provided at www.NEL.gov. The reader also is directed to the original existing reports, which are referenced throughout the chapter, for additional information.

Four questions addressed dietary sodium intake. For Question 1, the Committee used the 2013  National Heart, Lung, and Blood Institute (NHLBI) Lifestyle Interventions to Reduce Cardiovascular Risk: Systematic Evidence Review from the Lifestyle Work Group1 and the associated American Heart Association (AHA)/ American College of Cardiology (ACC) Guideline on Lifestyle Management to Reduce Cardiovascular Risk.2 Although new studies examining the relationship between sodium and blood pressure have been published since the completion of the NHLBI review, including findings from the Prospective Urban Rural Epidemiology (PURE) study,3 the Committee determined the evidence presented in the SR conducted by NHLBI, linking sodium and blood pressure, was strong and that consideration of more recent findings would not change the conclusions. Thus, the Committee did not update the review. For Question 2, the Committee updated the NEL systematic review on sodium and blood pressure in children conducted by the 2010 DGAC. The data reviewed for this question by the 2010 DGAC included children, birth to age 18, and the 2015 DGAC updated the sodium review using the same age range. For Question 3, the Committee relied on the NHLBI systematic review from the Lifestyle Work Group1 as well as the 2013 Institute of Medicine (IOM) report, Sodium Intake in Populations.4 Additionally, because the quality and quantity of the evidence on sodium and cardiovascular disease (CVD) that was used in the two reports is limited, the Committee updated the sodium and CVD review using a NEL systematic review update from January 2013 to July 2014. The final question in the sodium section, Question 4, also was answered using the recent NHLBI systematic review from the Lifestyle Work Group.1 The Committee also used the 2010 IOM Report on Strategies to Reduce Sodium Intake in the United States to inform the implications statements for these questions.5 

Regarding saturated fat, Question 5 was answered using the NHLBI systematic review1 and related AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk,2 which focused on randomized controlled trials (RCTs), as well as existing SRs and MA  addressing this question published in peer-reviewed literature between January 2009 and August 2014. Particular emphasis was placed on reviews that examined the macronutrient replacement for saturated fat.

The remaining questions in this chapter examined added sugars and low-calorie sweeteners. For Question 6, the DGAC relied on systematic reviews commissioned by the World Health Organization (WHO) to address body weight6 and dental caries.7 Additionally, to capture new research, the Committee searched for SRs and MA published since January 2012, the completion of the WHO reviews. Type 2 diabetes was not addressed by the WHO, and therefore, the Committee relied on existing SRs/MA published since January 2010 to address this health outcome. No existing SRs/MA examine added sugars and CVD, so the Committee conducted an original NEL systematic review to address this question (see http://NEL.gov/topic.cfm?cat=3376 for complete information on this review). Question 7 on low-calorie sweeteners was answered using existing SRs/MA published from January 2010 to August 2014. For low-calorie sweeteners, the Committee was initially interested in the health outcomes of body weight, type 2 diabetes, CVD, and dental caries. However, existing reviews were available only for body weight and type 2 diabetes. The Committee did not conduct an original NEL systematic review on CVD or dental caries because of limited time and resources, and because the Committee did not think sufficient evidence was available to address these health outcomes.

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