The Dietary Guidelines-What Goes on Under the Plate?

Written by: Louise Calderwood   |   March 19, 2020

Ensuring a stable food supply, Federal agencies

I clearly remember one of my early classes as an animal science student at the University of Vermont, ASCI 141 - Feeds and Feeding. Throughout the semester, Dr. Jim Welch walked us through the formation of diets for every stage of growth, pregnancy and lactation for a number of livestock species. As earnest students, we agonized over the correct combination of forages, grains and mineral mixes to meet the exact nutrient requirements for a lactating sow or a weaned dairy calf. We carefully balanced the availability of an ingredient with its cost and benefit to the intended animal. In our homework exercises, ounces and pennies would impact our decisions and the validity of our answers. We rigorously defended our answers and challenged anyone, including Dr. Welch, to question our findings.

Fast forward (more than a few decades!) to the work of the 2019 Dietary Guidelines Advisory Council (DGAC) and its ground-breaking progress of adding human diets for birth to two years, pregnancy and lactation to its review of the United States’ dietary recommendations. The irony is not lost on this former student of animal nutrition that for over 100 years, animal diets have been carefully developed for these groups, but as a nation, we are just starting to address the impact that national dietary policies can have for Americans with the highest nutrient needs.

What is the function of the DGAC and how does it gather the information it uses to advise the work of the U.S. Department of Agriculture and the Food and Drug Administration on development of the next round of guidelines for American diets? And why is the process so fraught with contention? The American Feed Industry Association is following the work of the 2019 DGAC to assure science is used to review the use of animal protein in American dietary policy.

Members of the 2019 DGAC include academics from across the country who specialize in a wide array of nutritional sciences. When the 2015 DGAC released its report, some of the content received criticism due to the advisory committee's composition and the membership selection processes. Further questions were raised about the breadth of the 2015 advisory committee’s scope, the processes used to evaluate the evidence and the completeness of its work.

In response to the criticism of the 2015 process, the 2019 DGAC subcommittees developed lists of questions for the experts to explore using information gathered through the Nutrition Evidence Systematic Review (NESR), a team of scientists housed at the USDA’s Center for Nutrition Policy and Promotion who specialize in conducting systematic reviews on food- and nutrition-related topics. Using NESR as a resource assures the 2019 DGAC is addressing important public health questions and using transparent methods to synthesize the body of scientific evidence on topics relevant to federal policy and programs.

Some, including the National Academy of Sciences, Engineering and Medicine have found fault with having all of the 2019 DGAC questions filtered through the NESR. The 2015 DGAC utilized NESR’s predecessor, the Nutrition Evidence Library, for reviews to answer only 27% of its questions. Critics of the 2019 DGAC research system feel that not using existing systematic reviews and meta-analyses that are high-quality, relevant and timely will eliminate many studies that incorporate pre-2000 evidence and provide examples of  dose-response patterns that may not be apparent if the research is only assessed using systematic literature reviews conducted by the NESR. One example of concern is the impact of alcohol consumption on the prevalence of certain types of cancer.

The 2015 DGAC process strayed into commenting on the perceived environmental impact of dietary choices and the sustainability of the American diet. Late in 2015, the secretaries of the USDA and Human and Health Services issued a joint statement stating that the 2015 dietary guidelines were not an appropriate vehicle for a policy conversation about sustainability. The inclusion of sustainability has been limited in the 2019 DGAC process.

In May, the 2019 DGAC will submit its report to the USDA and FDA for development of the actual dietary guidelines to shape U.S. nutritional policy for the next five years. And once the air clears and we sift through the strident agendas, I will think back to my days of developing those dairy calf diets and how simple it all seemed in hindsight.