“There’s a lot of stuff in the Guidelines that was right 40 years ago but that science has disproved. Unfortunately, sometimes, the scientific community doesn’t like to backtrack.”
That was David McCarron, nutrition researcher at the University of California-Davis nearly two years ago, commenting on the U.S. Congress ordering a comprehensive review of the way the Dietary Guidelines for Americans have been developed (“Congress: We need to review the Dietary Guidelines for Americans,” Washington Post, December 18, 2015). The Dietary Guidelines have been issued since 1980 by the U.S. Department of Agriculture (USDA) and Department of Health and Human Services (HHS) to set dietary standards for school lunch and military meals, as well as set standards for American food producers and meal providers that affect other countries.
We would agree with McCarron that the scientific community doesn’t like to backtrack. We would disagree with the premise that a “lot of stuff” in the Guidelines was right 40 years ago. Unfortunately, it has taken 40+ years to get to the point where nutrition professionals questioned the lack of science, compared the theory with the overall problems of obesity, diabetes and heart disease and convinced Congress that the federal government’s methods of developing Dietary Guidelines needed overhauling.
Last May, we talked about the book by Nina Teicholz, The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet. Teicholz explained how the low-fat, high-carbohydrate, fewer-animal-products theory came to be, based on faulty science and big political influence. Soon after the book’s release, she began warning animal agriculture about the next set of Dietary Guidelines being finalized in 2015. Her information was that this Dietary Guidelines Advisory Committee (DGAC) was very radical and was considering more restrictions on — or even elimination of — red meat in the Guidelines.
When the Guidelines were issued, the fears of many nutritionists and health experts were realized. The lack of scientific rigour, inappropriate handling of data and stubborn adherence to old theories created controversy, especially in the U.S. and Great Britain. The uproar brought on a congressionally mandated study of the process.
The National Academies Committee validated the concerns of scientists and food industry people. The report found shortcomings in scientific rigour. Conclusion: The process needs to be redesigned.
The process really breaks down into three parts: updating and enhancing the Nutrition Evidence Library with all the relevant research and clinical data, the selection of the Dietary Goals Advisory Committee and the deliberation on the issues deemed most important. In the past, while biases and conflicts of interest were obvious, they were not officially acknowledged or addressed. The National Academies Committee recommended that both financial and non-financial conflicts of interest be identified and noted for nominees; and transparency and proper management be followed in handling conflicts of interest. The committee further recommended a third party be hired to review the normal 150-200 nominations and reduce the list to 30-40. USDA and HHS departmental review would reduce the provisional list down to as many as 17 to be subjected to public comment.
Another key criticism up to now has been potential bias on the part of staff who decide which studies are entered in the National Evidence Library. Many more recent studies have not been included. First, the committee recommends a Dietary Guidelines Planning and Continuity Group for strategic planning, ongoing monitoring of evidence and topic prioritization. Second, technical expert panels should be used to provide content and methodological consultation during evidence evaluation.
That last point is likely poorly understood and a critical cog. During the National Academies Committee presentation of the report, committee member Bruce Lee from Johns Hopkins Bloomberg School of Public Health several times made the point that evaluating meta-studies, where the data is gathered from dozens of smaller studies, requires a modern, systematic approach using sophisticated software to account for the multiple factors and variations from multiple streams of data.
The third party would be a Dietary Guidelines Scientific Advisory Committee to interpret the scientific evidence, draw conclusions and write Dietary Guidelines. There should be explicit and transparent standards for developing evidence-based guidelines and recommendations. Rationale for decisions should be clearly stated and omissions or deviations should be explicitly outlined by the secretaries of USDA and HHS.
The report also acknowledged that diet constitutes an extremely complex system of exposure that is known to influence health, and modeling can help to make sense of that complex system. Food pattern models should be enhanced to better reflect the complex interactions involved as well as the range of health diets.
The National Academies report did not make any comment on the 2015 Guidelines themselves. But by separating out control of the evidence library and topic selection, separating out the screening of Advisory Committee members and putting real teeth into bias and conflict of interest disclosures and forcing some scientific standards onto the Scientific Advisory Committee, should Congress and the departments adopt these recommendations, we have a much better chance of having scientific, evidence-based Dietary Guidelines and clues to a healthier population.