Friday, September 25, 2015

US Dietary Guidelines for Americans

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, with most Western 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...

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 US Department 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.4 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 from industry in 2012, and the AHA reported 20% of revenue from industry in 2014. Potential conflicts of interest include, for instance, decades of support from vegetable oil manufacturers, whose products the AHA has long promoted for cardiovascular health. This reliance on industry backed groups clearly undermines the credibility of the government report...

The overall lack of sound science and proper methods in the 2015 report could be seen as a reluctance to depart from existing dietary recommendations. Many experts, institutions, and industries have an interest in keeping the status quo advice, and these interests create a bias in its favor. Abandoning the NEL review methods, as the 2015 committee has done, opens the door not only for bias but also for influence from outside agendas and commercial interests, and all of these can be observed in the report.

For example, a bias towards the longstanding view that saturated fats are harmful can be seen in the report’s designation of them, together with sugar, as a new category it calls “empty calories.” The report repeatedly mentions the need to reduce “sugar and solid fats,” because, “both provide calories, but few or no nutrients.” Yet this pairing is unsupported by nutrition science. Unlike sugar, saturated fats are mostly consumed as an inherent part of foods such as eggs, meat, and dairy, which together contain nearly all of the vitamins and minerals needed for good health.

Not following the NEL methods has also allowed outside agendas to enter into the report, most clearly in the form of the new consideration for environmental sustainability. Although, as the report states, the environmental effects of food and drink production are considerable, they are outside the committee’s formal mandate to provide the federal government with the “current scientific evidence on topics related to diet, nutrition, and health.” In a new development for 2015, the USDA hired a food policy analyst focused on environmental issues to oversee the guideline committee’s work, reflecting a new agenda in the process.

Teicholz N. The scientific report guiding the US dietary guidelines: is it scientific? BMJ. 2015 Sep 23;351:h4962.
Courtesy of:

1 comment:

  1. On Wednesday, a congressional hearing will take up the new, proposed U.S. Dietary Guidelines, a process that has always been political, but perhaps never more so than it is now.

    The proposed guidelines, a 570-page report, were authored by the Dietary Guidelines Advisory Committee, an independent group of 14 appointed doctors and scientists, working under the auspices of the departments of Agriculture and Health and Human Services. The report’s basic advice might sound innocuous enough: the American diet, according to the committee’s report, should be high in fruits, vegetables, whole grains, seafood, nuts, and legumes, moderate in low-fat dairy products, low in red and processed meat, and very low in sugar and refined grains...

    Adding fuel to the fire, last month an article was published by the medical journal The BMJ, charging that the advisory panel behind the guidelines based them on outdated science, and are too critical of high-fat, low-carbohydrate diets. The article — presented as an “investigation” of the advisory panel — was written by Nina Teicholz, a journalist and author of “The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.” At the heart of Teicholz’s argument is that the panel omitted research that shows saturated fats aren’t as bad as once thought and that a low-carb diet might be beneficial; the writer argues in her piece that there is “a reluctance by the committee behind the report to consider any evidence that contradicts the last 35 years of nutritional advice.”

    The article drew a lot of heat, including from Marion Nestle, a well-known nutritionist and author of “Food Politics” and “What to Eat.” While Nestle agrees that the advisory committee should be driven entirely by science and fact, she wrote on her blog:

    What troubles me about Teicholz’s work is the certainty with which she presents her ideas. She comes across as utterly convinced she is right, even in the face of substantial and substantive criticism of her statements and interpretations.

    Such criticism has come from the likes of Rosemary Stanton and Tim Crowe, a pair of nutritionists in Australia, who wrote a scathing response to Teicholz’s article. They addressed Teicholz’s charge that the panel was influenced by the food industry with similar charges against her (and they noted that she has an interest in selling her book.)

    In terms of substance, they maintained that the advisory panel did, in fact, take recent research into account, but gave it the weight it deserves. On low-carb, they argued that there simply isn’t enough research, at least not yet, to strongly recommend such a diet. And, they wrote, the panel did address research indicating that saturated fats might not be so bad. But the committee, they said, emphasized which foods people replace saturated fats with...

    The problem, the nutritionists wrote, is that too many researchers and pundits are too focused on isolated nutrients and not focused enough on the sources of those nutrients.

    Members of Congress will now decide whether it makes a lot of sense to them.

    The guidelines affect everything from food labeling to school lunch menus to advice given by doctors. Every five years, the federal government reviews the guidelines, but as food has become a kind of political totem, with debates over “factory farming,” the marketing of unhealthful foods, and corporate food marketing, these dietary regulations have become a source of controversy.

    To get an idea of just how controversial the guidelines have become, consider that five years ago, the last time they were reviewed, they received about 2,000 public comments. This year, they have received 29,000. And the uproar from various industry groups has been loud enough to get Congress to consider whether to withhold appropriations for the issuance of the guidelines.
    Courtesy of: