The scientific report guiding the US dietary guidelines: is it scientific?

The expert report underpinning the next set of US Dietary Guidelines for Americans fails to reflect much relevant scientific literature in its reviews of crucial topics and therefore risks giving a misleading picture, an investigation by The BMJ has found. The omissions seem to suggest a reluctance by the committee behind the report to consider any evidence that contradicts the last 35 years of nutritional advice. Issued once every five years, the guidelines have a big influence on diet in the US, determining nutrition education, food labeling, government research priorities at the National Institutes of Health, and public feeding programs, which are used by about a quarter of Americans each year. The guidelines, which were first issued in 1980, have also driven nutrition policy globally, withmostWestern nations subsequently adopting similar advice. The guidelines are based on a report produced by a dietary guidelines advisory committee—a group of 11-15 experts who are appointed to review the best and most current science to make nutrition recommendations that both promote health and fight disease. The committee’s latest report was published in February and is under review by the government’s health and agricultural agencies, which will finalize the guidelines in the fall. Concern about this year’s report has been unprecedented, with some 29 000 public comments submitted compared with only 2000 in 2010. In recent months, as government officials convert the scientific report into the guidelines, Congress has sought to intervene. In June, it proposed a requirement that the guidelines be based exclusively on “strong” science and also that they focus on nutritional concerns without consideration of sustainability. Other debated topics include newly proposed reductions in consumption of sugar and red meat. These issues will likely come to a head at a Congressional hearing on the guidelines in October, when two cabinet secretaries are scheduled to testify. The BMJ has also found that the committee’s report used weak scientific standards, reversing recent efforts by the government to strengthen the scientific review process. This backsliding seems to have made the report vulnerable to internal bias as well as outside agendas. The 2015 report states that the committee abandoned established methods for most of its analyses. Since its inception, the guideline process has suffered from a lack of rigorous methods for reviewing the science on nutrition and disease, but a major effort was undertaken in 2010 to implement systematic reviews of studies to bring scientific rigor and transparency to the review process. The USDepartment of Agriculture set up the Nutrition Evidence Library (NEL) to help conduct systematic reviews using a standardized process for identifying, selecting, and evaluating relevant studies. However, in its 2015 report the committee stated that it did not use NEL reviews for more than 70% of the topics, including some of the most controversial issues in nutrition. Instead, it relied on systematic reviews by external professional associations, almost exclusively the American Heart Association (AHA) and the American College of Cardiology (ACC), or conducted an hoc examination of the scientific literature without well defined systematic criteria for how studies or outside review papers were identified, selected, or evaluated. Use of external reviews by professional associations is problematic because these groups conduct literature reviews according to different standards and are supported by food and drug companies. The ACC reports receiving 38% of its revenue