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Have better diets “saved more than one million people from dying”?

Better Diets May Be Extending Americans' Lives

Our Review Summary

Making the healthy choiceThis news story ably describes a Harvard research team’s effort to evaluate the quality of American diets over time using a composite index of food choices that reflect adherence — or lack thereof — to diets predicted to lower the population risk of heart disease, cancer and diabetes. The story does a pretty good job of explaining a mind-numbingly complicated collection of disparate data, as well as the research team’s overall conclusion: that improvements in U.S. diet between 1999 and 2012 — notably reduction in trans fats and red meat consumption, along with increased consumption of fruits, nuts and whole grains — may have pushed down the rates of premature deaths and chronic disease burden, although doing little to raise the overall “health” of the American diet. But the story swallows a bit too easily the claim that better diets “have saved more than one million people from dying prematurely.” While that’s certainly possible, the claim is based on modeling from observational studies that can’t prove cause and effect — so it’s inappropriate to suggest, based on these types of studies, that dietary changes “saved” anyone. These are associations but not proof that diets reduced death rates. In addition, the story could have been strengthened by a bit more emphasis on racial and socioeconomic disparities in the improvement rates; by adding some information about the links between public policy and dietary choices; and by delving a little deeper into the study’s limitations, which are outlined in substantial detail by the investigators. 

 

Why This Matters

Efforts to slow or stem the rising or persistent epidemics of obesity, diabetes, cancer and heart disease depend substantially on an educated public, ample healthy food choices and public policies that clarify and encourage healthy diets. One huge problem has been getting any clarity out of a jumble of often-contradictory dietary claims, unpopular or impossible-to-implement regulations (think bans of large-size sugary drinks), and a constant drum beat of newspaper, magazine, online and electronic stories that remind us endlessly that we are all going to dietary hell in a hand basket.  Stories about analytical efforts to put dietary changes in some perspective, and provide even a bit of clarity, are therefore much needed and welcome, not only by public health policy makers struggling to make a dent in our morbidity and mortality rates, but also by those who are footing the bills for the epidemics and the attempts to address them.

Criteria

Does the story adequately discuss the costs of the intervention?

Not Applicable

We are content to declare this Not Applicable, but it wouldn’t have hurt to note the financial burden and potential financial savings accrued from fewer chronic diseases and deaths and bends in the rates of disease burden. A sentence or two would have strengthened the story.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The major claim in the story is that better diets prevented more than one million premature deaths. But as noted above, this is an estimate based on a model derived from observational studies. Although better diets may be associated with lower death rates, there’s no way to tell based on these studies whether dietary changes caused the benefits that the story claims. The coverage should have been clearer about this.

Does the story adequately explain/quantify the harms of the intervention?

Not Applicable

It’s certainly possible that attempts to promote healthier diets could result in unintended harms. For example, some might argue (erroneously, in our view), that a tax on sugar-sweetened beverages, intended to promote healthier drink choices, would be regressive (i.e. disproportionately costly to lower income consumers). But we think a discussion of such issues is beyond the scope of this article, so we’ll rate it Not Applicable.

Does the story seem to grasp the quality of the evidence?

Satisfactory

Overall, the article did a fair job of describing the sources of the data, but it could have done more to bring credibility had it specifically mentioned some of the seven studies that made up the “index,” particularly NHANES which in some circles is a household name. In addition, we wish the story had made more specific mention of the fact that these were observational studies that are subject to important limitations. But since we’ve already mentioned that above, we won’t ding the story for that problem here. And the story does at least nod to the controversy surrounding the utility/validity of dietary recall data in these types of studies through comments from the quoted expert.

Does the story use independent sources and identify conflicts of interest?

Satisfactory

As noted, the article would have been stronger if it had quoted more senior authors of the paper and more outside experts, but it does quote one and the quote is strong.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

The story doesn’t discuss anything besides healthier diets that might have contributed to increased longevity during the study period. More widespread use of effective medications (e.g. statin drugs)? Lower smoking rates? More regular physical activity? A line or two would about other relevant trends would have been welcome.

Does the story establish the availability of the treatment/test/product/procedure?

Satisfactory

Except possibly for food deserts, healthy foods are generally available. The story makes the case that widespread consumption of healthier foods has had broad public health benefits.

Does the story establish the true novelty of the approach?

Satisfactory

The article hooks the reader with the idea that contrary to the “stereotype” of the unhealthy Americans and their greasy kid stuff diets, the study at hand suggests the “opposite” may be the case. While the researchers’ conclusions struck a balance between good news and bad news about our collective eating habits, and the article may have slightly overstated the “surprise” findings, the text does its job of getting readers’ attention and quickly qualifies the “good news” with a quote citing “huge room …for further improvement.”

Does the story appear to rely solely or largely on a news release?

Satisfactory

Health Affairs did publish a brief summary “news release” on its website, but the article clearly went beyond the release to report the story.

Total Score: 6 of 8 Satisfactory

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