US Government Dietary Guidelines, Unintended Consequences and Public Policy

04/02/08 In the years following the government promotion of a low-fat diet, obesity in America has reached almost epidemic levels. Were the federal guidelines a direct cause, a catalyst for unintended consequences or merely a well-meaning but unimportant factor? In a study published in the March 2008 issue of the American Journal of Preventive Medicine, Paul R Marantz, MD, MPH, Elizabeth Bird, AB, and Michael H Alderman, MD, all from the Albert Einstein College of Medicine, suggest that the government issued these recommendations based on limited scientific data and assumed that no harm would result, but the evidence now suggests otherwise. They caution that without proper studies, such guidelines may be harmful.

“When dietary guidelines were initially introduced in the late 1970s, their population-based approach was especially attractive since it was presumed to carry little risk,” says Dr. Marantz. “However, the message delivered by these guidelines might actually have had a negative impact on health, including our current obesity epidemic. The possibility that these dietary guidelines might actually be endangering health is at the core of our concern about the way guidelines are currently developed and issued.”

Dr. Marantz and colleagues argue that if guidelines can alter behavior, such alteration could have positive or negative effects. They cite how, in 2000, the Dietary Guideline Advisory Committee suggested that the recommendation to lower fat, advised in the 1995 guidelines, had perhaps been ill-advised and might actually have some potential harm. The committee noted concern that “the previous priority given to a ‘low-fat intake’ may lead people to believe that, as long as fat intake is low, the diet will be entirely healthful. This belief could engender an overconsumption of total calories in the form of carbohydrates, resulting in the adverse metabolic consequences of high carbohydrate diets,” the committee wrote, while also noting that “an increasing prevalence of obesity in the United States has corresponded roughly with an absolute increase in carbohydrate consumption.”

Dr. Marantz and colleagues present data that support these trends; however, they are careful to note that this temporal association does not prove causation. Instead, says Dr. Marantz, “it raises the possibility of a net harmful effect of seemingly innocuous dietary advice. These dietary recommendations did not necessarily cause harm, but there is a realistic possibility that they may have.”

In a commentary published in the same issue of the American Journal of Preventive Medicine, Steven H. Woolf, MD, MPH, from Virginia Commonwealth University and Marion Nestle, PhD, MPH, of New York University, maintain that the guidelines are supported by decades of research. While they agree with Dr. Marantz that people often compensate for low-fat intake by consuming more calories, they disagree that the guidelines were wrong to encourage low-fat diets. “The guidelines were not the culprit,” said Dr. Woolf, who believes that the government was right to share what was known about the dietary causes of disease.

Woolf and Nestle do not dispute that guidelines can have unintended consequences. However, they write, “When the prevailing message fails to achieve its intended aims or achieves the wrong ends, the solution is not to abandon the enterprise but to reshape the message to achieve desired outcomes.”

Continuing the dialog, Marantz, Bird and Alderman respond in a further commentary, “When trying to mitigate potential harm from past guidelines based on inadequate science, issuing ‘reshaped’ guidelines with similarly inadequate science merely perpetuates past mistakes. It might sometimes be best to avoid translating flaccid arguments into rigid guidelines. Ultimately, this boils down to a difference in world view, much like the distinction between clinicians guided by the therapeutic imperative and those guided by the maxim ‘first do no harm.’ Of course, when the evidence is clear, beneficial interventions are always favored, and harmful interventions always shunned. It is when the data are unclear that challenges arise.”

Marantz concludes, “As doctors, our first call is to do no harm. That’s why we recommend that guidelines be generous in providing information, but more cautious in giving direction. Any directions should be based on the very highest standards of scientific evidence. After all, we expect that much from pharmaceutical companies before they bring a new drug to market.”

The article is “A Call for Higher Standards of Evidence for Dietary Guidelines” by Paul R. Marantz, MD, MPH, Elizabeth D. Bird, AB, and Michael H. Alderman, MD. The commentary is “Do Dietary Guidelines Explain the Obesity Epidemic?” by Steven H. Woolf, MD, MPH, and Marion Nestle, PhD, MPH, followed by the author’s response by Marantz, Bird and Alderman. This exchange appears in the American Journal of Preventive Medicine, Volume 34, Issue 3 (March 2008) published by Elsevier.