Re: The scientific report guiding the US dietary guidelines: is it scientific?
The 2015 Dietary Guidelines Advisory Committee (DGAC) strongly disagrees with many of the statements represented as facts and the conclusions in the BMJ paper presented by journalist Nina Teicholz. It is imperative for the public to understand that the 2015 DGAC’s deliberative process was mandated by the U.S. Congress to provide advice to the U.S. Department of Health and Human Services (HHS) and Agriculture (USDA) in order to inform public policies that will appear in the upcoming Dietary Guidelines for Americans (DGA), 2015. The Committee was specifically charged to review the Dietary Guidelines for Americans, 2010 and determine topics for which new scientific evidence is likely available that may inform revisions to current guidance or suggest new guidance.
Ms. Teicholz states that the 2015 DGAC Committee overlooked much relevant scientific data and failed to provide details on its methodology and particularly how studies included in its review were “identified, selected and evaluated”.
The procedures used to develop the DGAC Scientific report are expansive, transparent, and thoughtful, with multiple opportunities for public input through open commentary, public meetings, and hearings. The 2015 DGAC spent 20 months reviewing the latest scientific evidence on nutrition and physical activity. It utilized four approaches including: 1. Original reviews conducted by the USDA’s Nutrition Evidence Library (NEL); 2. Existing, peer-reviewed high quality expert reports, systematic reviews and meta analyses of published literature; 3. Original analysis of U.S. population food and health data sets; and 4. Modeling analyses of USDA food patterns. Contrary to Ms. Teicholz’s assessment, the methods used for each research question were thorough and of the highest standards. The 2015 DGAC methodology is summarized in the 2015 DGAC Scientific report which can be found on-line at: http://health.gov/dietaryguidelines/2015-scientific-report/ and is supplemented with abundant on-line resource information including public comments at http://health.gov/dietaryguidelines/2015/ and for each NEL systematic review question at http://www.nel.gov/ .
Ms. Teicholz suggests that the 2015 DGAC applied “weak scientific standards” to grade the evidence that formed the basis of the Committee’s recommendations on food, nutrition and health.
This comment is completely unfounded. The 2015 DGAC’s methodology for scientific review and grading was highly rigorous and completely consistent with current and historic scientific practices used for developing evidence-based, expert guidelines including those of the U.S. National Institutes of Health (NIH), National Academy of Sciences, and Institute of Medicine as well as other scientific groups and government entities domestically and globally. When existing, published research formed the body of evidence for the DGAC’s conclusions and recommendations, it was formally graded using strict quality criteria (See for example http://www.nel.gov/topic.cfm?cat=3385 ). Note also, for example, that Part C of the 2015 DGAC Report clearly describes the process that the committee implemented to both identify and prioritize research questions, the approach used to consider when to commission the NEL or to conduct a systematic review, when to include existing reports, how the available evidence was determined to be of high quality and lastly, how the committee graded the overall evidence for each question and provided consensus for their recommendations. On page 54, we state “The scientific community now regularly uses systematic review methodologies, so, unlike the 2010 DGAC, the 2015 Committee was able to use existing sources of evidence to answer an additional 45 percent of the questions it addressed. These sources included existing high quality systematic reviews, meta-analyses, or reports. The remainder of the questions, 30 percent, were answered using data analyses and food pattern modeling analyses.”
Ms. Teicholz insists that the process used by the DGAC Committee was subject to members’ “internal bias” and “outside agendas” or relied on similarly suspect existing literature reviews conducted by professional organizations that she purports are supported by “food companies” or have other “conflicts of interest.”
This comment is highly misleading and unsubstantiated. Each member of the 2015 DGAC was nominated by their peers. Those nominated were rigorously reviewed. Those then chosen to serve were fully vetted according to strict federal guidelines including a thorough review to be certain that there were no conflicts of interest pertaining to this work.
As noted, when the 2015 DGAC used existing peer-reviewed systematic reviews or reports, they were identified by the NEL, Committee members or federal staff. Only reports and publications assessed to meet standards of high research quality were utilized. The vast majority of these reports came from the NIH and other federal agencies as well as the IOM, and not as suggested by Ms. Teicholz, from other sources such as professional organizations. In some cases, the federal reports that were utilized were subsequently endorsed and/or published by professional organizations.
In terms of the Scientific Reports findings, Ms Teicholz criticizes the Committee’s conclusions on saturated fat, red meat, salt, and added sugars and dietary carbohydrates and states that the report failed to “consider any evidence that contradicts the last 35 years of nutritional advice.”
These criticisms are unfounded and the conclusion reached is utterly untrue. For example, as it pertains to saturated fat, the Committee reviewed evidence from seven systematic reviews or meta-analyses published between January 2009 and August 2014 in peer-reviewed journals, which included RCTs and/or prospective cohort studies. Ms. Teicholz suggests that we did not consider the Women’s Health Initiative (WHI) in this review. In fact, one of the systematic reviews that was utilized summarized results from the WHI on the efficacy of low-fat interventions.
Based on the cumulative evidence, the committee drew the following conclusions:
• Strong and consistent evidence from RCTs and statistical modeling in prospective cohort studies shows that replacing SFA with PUFA reduces the risk of CVD events and coronary mortality.
• Reducing total fat (replacing total fat with overall carbohydrates) does not lower CVD risk.
In terms of Ms. Teicholz’s criticism of the Committee’s review pertaining to low-carbohydrate weight reduction diets, it is completely off base. Although many RCTs have examined the efficacy of low-carb diets vs. other diet interventions on weight loss, very limited data exist on the long-term health effects of low-carb diets.
The BMJ report is also highly misleading by stating that the 2015 DGAC continues to recommend low-fat high carb eating patterns. The DGAC report explicitly states that “dietary advice should put the emphasis on optimizing types of dietary fat and not reducing total fat” and that “The consumption of ‘low-fat’ or ‘nonfat’ products with high amounts of refined grains and added sugars should be discouraged.” The report further points out that “simply reducing SFA or total fat in the diet by replacing it with any type of carbohydrate is not effective in reducing risk of CVD”.
Ms. Teicholz also suggests that an outside food policy analyst was used to oversee the DGAC’s work relating to food insecurity and sustainability.
This conclusion reflects a lack of understanding of the process by which expertise is obtained to inform the Report. Federal guidelines permit the DGAC to consult experts on specific topic areas as needed. This process is open and transparent and posted at www.dietaryguidelines.gov . The 2015 DGAC did include two expert consultants on food policy and one on behavioral intervention strategies; their input was invaluable. Consultants must be vetted by federal staff and undergo the same conflict of interest screening as full committee members. Neither consultants nor committee members are paid for their time and expertise. Importantly, expert consultants were not voting members of the Committee nor did they at any time oversee the DGAC’s work.
In our opinion, Ms. Tiecholz’s article is woefully misleading and in many cases, factually incorrect. Its provenance is described as ‘commissioned’ and externally peer reviewed and fact checked. This statement is puzzling in its lack of detail and the validity of the statement on fact checking is doubtful. Ms Teicholz is a self-identified investigative reporter who has been on a quest for quite a long time to promote her own book in the popular press entitled ‘The Big Fat Surprise’ Why butter, meat and cheese belong in a healthy diet.’
In conclusion, the 2015 DGAC Scientific Report was developed in an open, evidence-based and transparent process that meets or exceeds the recommended scientific methods for issuing evidence-informed public health guidance. It is a disservice to these rigorous processes to publish commentaries that lack any scientific rigor and are inflammatory in nature. This publication without even a counterpoint detracts from the focused efforts needed to seek sound solutions to the preventable health problems we confront in the U.S. but also globally.
Submitted September 23, 2015
The 2015 DGAC Chair: Barbara Millen, Dr. PH, RD, Vice Chair: Alice Lichtenstein, DSC; Members: Steve Abrams, MD, Lucile Adams-Campbell, PhD; Cheryl Anderson, PHD, MPH, MS; J. Thomas Brenna, PhD; Wayne Campbell, PhD; Steven Clinton, MD, PhD; Frank Hu, MD, PhD; Miriam Nelson, PhD; Marian Neuhouser, PhD, RD; Rafael Perez-Escamilla, PhD; Anna Maria Siega-Riz, PhD, RD; Mary Story, PhD, RD
Competing interests: No competing interests