The scientific report guiding the US dietary guidelines: is it scientific?BMJ 2016; 355 doi: https://doi.org/10.1136/bmj.i6061 (Published 02 December 2016) Cite this as: BMJ 2016;355:i6061
Notice of correction and clarification
Please note that there has been a previous correction for this article, at http://www.bmj.com/content/351/bmj.h5686.
This article (BMJ 2015;351:h4962, doi:10.1136/bmj.h4962) stated that the 2015 US Dietary Guidelines Advisory Committee (DGAC) “conducted an [ad] hoc examination of the scientific literature without well defined systematic criteria for how studies or outside review papers were identified, selected, or evaluated.” The article also stated that the committee “conducted ad hoc reviews of the literature, without defining criteria for identifying or evaluating studies.” These statements are incorrect. The DGAC defined the methods it used for identifying, selecting, and evaluating such evidence in its advisory report1 in Part C: Methodology and Appendix E2.2 However, it should be noted that the DGAC also used non-systematic approaches in its evidence selection.
The article also stated that the DGAC’s recommendations on saturated fats were based, in part, on “the 2015 committee’s ad hoc selection of seven review papers,” and that “papers on saturated fats published since 2010 were covered by the committee’s ad hoc review, which did not use a systematic method to select or evaluate studies.” These statements are incorrect. Appendix E2.43 of the DGAC report defines the search strategy and inclusion criteria for the committee’s selection of papers for this topic and gives the DGAC’s quality rating (using AMSTAR, the methods of which were also described in Part C: Methodology of the report).
The article’s data supplement Table D includes the phrases “DGAC ad hoc selection” and “DGAC ad hoc review” of the literature, under the sections “dietary patterns and heart disease” and “dietary patterns and obesity,” respectively, and notes that “no systematic methodology is given for the selection of these studies.” This is incorrect. The prespecified search strategy and inclusion criteria are described in Appendices E2.26 and E2.27, respectively.
The article also stated, in reference to evidence regarding DGAC’s recommended diets and heart disease: “The committee reviewed other, more recent studies but not using any systematic or predefined methods.” This is incorrect. The DGAC defined its methods in Appendix E2.26, including search strategy, inclusion criteria, and quality rating (using AMSTAR, the methods of which were also described in Part C: Methodology of the report).
The BMJ’s press release for the article made a similar statement, quoting Fiona Godlee as saying “the [DGAC] has abandoned standard methodology.”3 This requires similar correction, as explained above.
The article stated that the committee did not systematically review certain studies on saturated fats from the 1960s and 1970s. This statement was insufficiently clear. It should have stated that the committee did not “directly” review these studies. The committee did consider two systematic reviews4 5 that themselves included five6 7 8 9 10 of the six trials mentioned in the article.6 7 8 9 10 11
The article also stated, “There have been at a minimum, three National Institutes of Health funded trials on some 50 000 people showing that a diet low in fat and saturated fat is ineffective for fighting heart disease, obesity, diabetes, or cancer. Two of these trials are omitted from the NEL review.” This statement was insufficiently clear. The two trials referred to12 13 were indeed omitted from the NEL’s 2010 review, as stated in the article, but it should be noted that they were evaluated in a Cochrane review,4 and that this review was considered by the committee in its 2015 advisory report.1 In addition, the two trials evaluated the effects of diet modification on serum lipids as a proxy for heart disease.12 13
The article also stated, regarding the Nutrition Evidence Library (NEL), that “a systematic review on health and red meat has not been done. Although several analyses look at ‘animal protein products,’ these reviews include eggs, fish, and dairy and therefore do not isolate the health effects of red meat, or meat of any kind.” This statement requires clarification. Several of the NEL reviews used “meat” as a search term and presented and discussed results of individual studies of red meat and total meat.14 15 16 17 18 19