The new scientific approach to the federal dietary guidelines

The chief scientific adviser behind the new US federal dietary guidelines speaks with us about her experience translating research into policy.

MillenThe US federal government has released a new set of dietary guidelines, which shift emphasis away from individual nutrients to focus on broader dietary patterns. Barbara Millen, chair of the project’s scientific advisory committee, explains how advances in research and fresh scientific perspectives are setting a new course to fight diet-related disease in the United States.

ResearchGate: What role did the scientific committee you chaired play in updating the dietary guidelines?

Barbara Millen: We were charged with assembling and reviewing the recent literature on topics related to the nutrition and health of the US population, forming conclusions and recommendations, and grading the quality of the evidence in these areas. Out of this process comes a detailed report for the Secretaries of Health and Human Services and US Department of Agriculture. So, it’s our job to look at the scientific evidence and draw conclusions, but we are not directly involved in the development of the guidelines themselves as a policy document.

RG: And what were the major findings you included in your report?

Millen: The report is broken down into a framework of five thematic areas. The first of these relates to the quality of the US diet and the status and trends in diet- and lifestyle-related health concerns in the population. We found a very high prevalence of diet-related chronic diseases; about half the population is affected. And about 70 percent of the population is overweight or obese. Second, we considered how dietary patterns relate to these health outcomes. We looked at major chronic disease outcomes: heart disease, hypertension, stroke, overweight and obesity, diabetes, diet related cancers. We also included important, but less prevalent health outcomes like bone health, neuropsychological disorders, and congenital anomalies. What we were able to do—which was very exciting and new in the report—was identify the common features of a healthy dietary pattern that leads to beneficial outcomes across most if not all of these areas.

The healthy pattern is higher in fruits, vegetables, whole grains, nuts and seeds, seafood, and low- and non-fat dairy. It is moderate in alcohol—if it’s consumed at all—and lower in red and processed meats. It is lower in saturated fat, with polyunsaturated fat being substituted for saturated fat, and lower in sodium and added sugars. We were able to not only conclude what the characteristics of these diets were, but also to model three different options—Mediterranean, “healthy American,” and vegetarian—that American consumers can utilize in shaping their diet into a healthier overall dietary pattern.

“We wanted to go into new realms that earlier dietary advisory committees had not looked at in as much detail.”

RG: The committee’s other areas of focus are somewhat less traditional for a dietary guidelines report. Can you tell us about those?

Millen: In the next two thematic areas, our report evaluated just how effective we understand individual-level behavior change to be and we point out that professionals—particularly nutrition professionals, dietitians, and multidisciplinary teams—are effective in promoting that individual-level change. We also considered how environmental settings, places like schools and workplaces, can improve dietary intake and physical activity in populations.

Finally, we looked at food safety and sustainability and concluded that the dietary pattern that we modeled for human health is also the dietary pattern that’s emerging in population research as being environmentally friendly. So it’s not only healthy for individuals and populations, but also the planet from the standpoint of conserving resources and reducing harmful emissions. We also had some updated guidelines on household food safety.

This is a very broad scope, but we wanted to go into new realms that earlier dietary advisory committees had not looked at in as much detail.

“We looked at the totality of evidence.”

RG: Let’s look a little more closely at one of the specific recommendations. Maybe the decision not to specify an upper limit on cholesterol intake?

Millen: I think that’s an area where the research has evolved. We’ve historically had an upper limit on cholesterol that reflected clinical research on the relative effect of saturated fat, polyunsaturated fat, and cholesterol. But even in that historic literature it was known that the impact of cholesterol was not as great an influence as saturated fat and polyunsaturated fat. The interpretation of the committee was that at the current levels of cholesterol intake in our population, which are 200 mg or less, the further reduction in cholesterol is not going to have a significant impact because of its relative influence on plasma levels. The decision was made to not carry the recommendation forward, because when you model a pattern that is lower in saturated fat and you’re achieving the other targets that we included, cholesterol intake is already going to be relatively low.

RG: Scientific studies can often contradict one another. How did the committee decide on recommendations in areas where results and conclusions were mixed?

Millen: We looked at the totality of evidence and determined the strength of that evidence. For recommendations that were rated as “strong,” the evidence was of high quality and consistent across the studies examined. Where “moderate” grades were assigned, we noted some inconsistencies or weaknesses of the evidence, but deemed it sufficient for a recommendation. Our conclusions and recommendations were debated and voted on publicly as part of the transparent process that Congress mandates.

If all you read are those bullet points, you’re not getting the full picture.”

RG: Is there anything from your report that didn’t make it into the guidelines that you would have liked to see included?

Millen: The language “lower in red and processed meats” could have been featured more prominently, though it is included in a call-out box.  Also, I would have liked greater attention paid to food security and sustainability, particularly from a long-term perspective. But we knew from the congressional hearings that, while the USDA considers environmental sustainability an important topic, they don’t really see it as subject matter for the dietary guidelines. Still, we had hoped that our recommendations in this area would appear there, or at least an acknowledgement that the healthy dietary pattern for individuals also happens to be a more environmentally friendly diet because of its focus on plant foods and the fact that it’s lower in red and processed meats. I would also have liked stronger wording on the importance of disease prevention in clinical and public health settings and also more acknowledgement of the professionals that are effective at influencing individual change.

Key Recommendations
Key recommendations from the USDA/HHS guidelines use the language “variety of protein foods, including seafood, lean meats, and poultry” rather than the more explicit “lower in red and processed meats” that appears in the advisory committee’s report.

However, I would say that the final guidelines do reflect most major highlights of our report overall. They emphasize the importance of diet-related disease and the role of nutrition and dietary patterns in prevention. They emphasize concerns about the costs that these conditions are causing in our healthcare system. They definitely emphasize the dietary pattern options that Americans can follow to achieve healthy food and beverage intakes. And they mention—and this was really important—that we all have a role to play both in influencing individuals to achieve healthy dietary patterns and physical activity levels, and in designing community settings to be more conducive to healthier lifestyles.

“We’ve had so many expert groups point us in the right direction, and now we need to act.”

RG: What was it like seeing your scientific recommendations transformed into a policy document? Do you think industry influence or other political considerations had an impact on the end result?

Millen: If you only read the 5-6 bullet points, it can seem like the dietary guidelines missed some of the major parts of our report. But when you look at the document in detail, you do see all five themes from our recommendations, with the exception of the sustainability piece. The bullet-point summary is a translation of those the five themes into major actionable points. They make it easy to understand what the targets are in terms of dietary pattern, which is really the core of the dietary guidelines. Our report was an enormous body of work, and I was so impressed at the quality of evidence that allowed us to make such a strong set of recommendations. For the most part, those recommendations appear in the dietary guidelines. I realize that my point of view on that is different than controversies raised in the press recently, and I would just say that if all you read are those bullet points, you’re not getting the full picture.

I hope we don’t continue to dwell on the controversy. Focusing on who won, who didn’t win is ridiculous. While debate can be healthy, we need to get beyond the heated arguments.  If we don’t, we won’t address the important, preventable problems we face as a nation. As our report and the guidelines say, we all have a role—from industry to public health professionals to research communities. We’ve had so many expert groups point us in the right direction, and now we need to act.

Featured image courtesy of Mark Turnauckas.