5 questions about dietary guidelines and an ‘impossible restriction’

Here’s the paradox: The most influential set of rules for the foods we eat are the ones most of us ignore. But they still matter for millions of  Americans.

The Dietary Guidelines for Americans, reviewed and issued by the federal government every five years, have broad impact on what goes into federal nutritional assistance programs, from WIC for women and young children to school lunches to meals for veterans or seniors. Yet 63% to 90% of people in the United States, depending on the nutrient, exceed recommended levels for added sugar, saturated fats, and sodium; 75% fall below standards set for vegetables, fruits, and dairy.  

Last week, an advisory panel made up of academic researchers met for two days of public discussion on what the next set of dietary guidelines should include. Their draft recommendations will go to the U.S. Department of Health and Human Services and the U.S. Department of Agriculture, after which final guidance will be released at the end of the year. 

On Monday the committee, or DGAC, said it did not include alcoholic beverages because a group within HHS and the National Academies of Sciences, Engineering, and Medicine is already engaged on that question. Ultra-processed foods are not part of the proposals for the 2025-2030 guidelines for a different reason: The committee found too little high-quality evidence to support any guidance. 

It may seem like two days of presentations after almost two years of reviewing the scientific literature produced little in the way of concrete changes, so STAT asked three experts for their takes.

How important are these recommendations?

Grace Chamberlin, policy associate, Center for Science in the Public Interest: The dietary guidelines are one of the largest levers that we have in this country to improve diets and health and the food system, so they matter a great deal. I mean, the dietary guidelines have been referred to as kind of a north star of the federal nutrition programs.

Marion Nestle, emeritus professor of nutrition and public health at New York University: Nobody pays much attention to them in practice. Also, they never change, really. In 1980 they said eat more vegetables, eat fewer foods high in fat, sugar, and salt. They still do.

Will it just take time for answers to be reached on ultra-processed foods, for example?

Nestle: We now have two controlled clinical trials on ultra-processed foods both showing that people who eat diets based on these foods take in tons more calories… than people eating relatively unprocessed diets.  What more do you need to know?  The DGAC is ignoring these trials because their duration was short.

When I was on the DGAC in 1995, we were instructed to review the science and do the best we could to interpret its meaning for dietary advice for the American public. This assumed that the evidence would be difficult to interpret and incomplete. That changed with the 2005 guidelines.  Since then, committees have been instructed to make evidence-based recommendations, and only do so. This is an impossible restriction as the situation with ultra-processed foods indicates. 

JoAnn Manson, professor of medicine at Harvard Medical School and Brigham and Women’s Hospital: I think it’s important to have rigorous evidence before giving guidelines on it. And I think one of our findings was the diversity of ultra-processed foods: It definitely was not one size fits all. I suspect that the ultra-processed foods will be in the 2030 dietary guidelines. I think it’s probably going to take another several years to have a sufficient evidence base but I think it’s going in that direction.

Chamberlin: We generally agree with the DGAC draft conclusions on the topic. More research is needed to clarify what exactly is driving the link between ultra-processed foods and weight gain or other health outcomes. And so I think that that is certainly a research gap to address. Ultra-processed food consumption has been associated with increased risk of cardiovascular disease, mortality, and type 2 diabetes. But it’s unclear which aspects of ultra-processed foods are causing those health effects.

What can be done about limited evidence?

Nestle: Everyone underestimates how difficult nutrition research is to do. Just think about it. You can’t lock people up for decades to study what they eat under controlled conditions. You have to trust people to say what they are eating (everyone lies or, more politely, can’t remember). The studies are necessarily observational and can’t prove causation.

Chamberlin: So long as we’re relying on these clinical trials, it’s going to be difficult to reach strong conclusion statements, given the scientific rigor and standards that the DGAC holds themselves to, to only make recommendations based on the research that exists. And the current research lacks evidence on pregnancy and postpartum, children and adolescents and critically, many racial and ethnic subgroups. I think really what they’re putting out in those public meetings, whether intentionally or not, is a huge call to the research community to make sure that the next time we do this, there is the research that is needed to underlie strong conclusions.  

What do you think the committee has added to the discussion?

Chamberlin: This dietary guidelines advisory committee did a really remarkable job starting to integrate health equity into this process. They presented really incredible progress to the best of their ability on trying to integrate more diverse research samples and protocols and doing specific pilot food patterns. They’re going through food pattern modeling of such specific diets like the American Indian and Alaska Native diets. 

Manson: I think that the research on dietary patterns has been very helpful, identifying certain patterns that allow for flexibility, including some of the cultural influences and cultural differences can really make a difference in not forcing people into these very restrictive types of recommendations. People really want to have latitude. They may understand that certain foods should be consumed less frequently or infrequently, but they don’t want them to be totally taboo.

What’s missing?

Chamberlin: [The committee is] limited by the research that exists for making sure they have nationally representative data. There has to be adequate funding and time to have diverse samples of populations. That’s really important so that we can have more information about culturally inclusive diets and about having all of these different conclusions really broken down by race and ethnicity and make sure that we’re not widening any health disparities.

We are disappointed that the DGAC didn’t clarify or reaffirm the quantitative limits on saturated fat and added sugar. And that is not because of a lack of research or evidence-based base. They kind of failed to bring that up in the meeting. So we are definitely interested in learning what their recommendations will be for quantitative limits on those.

STAT’s coverage of chronic health issues is supported by a grant from Bloomberg Philanthropies. Our financial supporters are not involved in any decisions about our journalism.

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