2015 DGAC Report: Limitations of the Science

Monday, March 23rd, 2015 |

2015 Dietary Guidelines Advisory Committee Report Critical Analysis

Effective policy demands a rigorous and unbiased review of the science along with an honest assessment of uncertainties and contradictions in available evidence. Important aspects of the recommendations in the 2015 DGAC Report remain unproven and thus do not meet the requirements for sound policy formation.  Recommendations in the Report:

  • fail to acknowledge conflicting data; scientific controversy is presented as “settled.”
  • report contradictory or conflicting results
  • fail to use consistent, transparent and replicable methodology
  • fail to restrict policy recommendations to populations studied

This document risks further undermining public trust in health recommendations. Americans deserve a transparent acknowledgement of the limitations of nutrition science rather than continued promotion of inconsistent, contradictory, and ineffective dietary advice. When coherent conclusions cannot be drawn, policymakers must act according to the principle, first and foremost, to do no harm.  Lack of adherence to this principle has led to policies, such as recommendations to reduce dietary cholesterol and fat, that are strongly associated with increases, rather than decreases, in obesity and chronic disease. These policies were based on insufficient and inconclusive science and have led to negative unforeseen consequences.

The following key policy recommendations present conflicting and ambiguous conclusions.

Low-fat diet:  While the DGAC acknowledged that “low-fat diets induce dyslipidemia” (Meeting 5 Summary), the Report fails to recognize the role of federal dietary guidance in the promotion of low-fat diets.  In addition, several inconsistencies and contradictions remain.

  •  There is no explicit discussion of overall fat in the Report, leaving the public to assume that limits on fat remain in place.
  • All dietary patterns in the Report recommend low-fat or fat-free products.
  • The dietary patterns recommended in the Report are, in terms of nutrient content, low in fat and high in carbohydrate.

Cholesterol: The Report does not place any limits on dietary cholesterol as in previous Dietary Guidelines.  In contradiction of this conclusion, information contained throughout the Report continues to suggest that dietary cholesterol should be limited.

Saturated fat:  The Report recognizes the ongoing controversy over saturated fat, yet identifies saturated fat as an “overconsumed nutrient of concern” based on assumptions that acknowledge only one side of the debate. Comparisons using the Report’s own data indicate that carbohydrate is more “overconsumed” than saturated fat and is also a “nutrient of concern” with regard to metabolic risk factors.

Grains:  Conclusions regarding grains are contradictory and confusing. They also fail to acknowledge that carbohydrate, the primary nutrient in grains, is overconsumed by Americans.

  •  The Report recommends “lower intakes of refined grains, and sugar-sweetened foods.”
  • At the same time, the Report recommends 3 ounces of refined grains per day, the same amount as is recommended for whole grains.
  • This amount of refined grains is identical to previous guidance and contradicts the recommendation for “lower intakes” of refined grains.

Sodium:  Restrictions on sodium are based almost exclusively on relationships between sodium and blood pressure. Associations between sodium intake and health outcomes are based only on observational reports, which according to a recent IOM report, are inconclusive.

Meat:  Conclusions regarding meat are contradictory and confusing. They fail to acknowledge meat as an important and preferred source of key nutrients, particularly for populations at risk.

Vulnerable Populations:  The Report applies a single dietary approach to all Americans over the age of one despite insufficient evidence for this generalization.  Children, pregnant women, the elderly, and minority populations are most likely to be affected by federal programs related to nutrition, but research on diet-disease relationships in these groups is particularly limited

  •  The Report acknowledges that “very little is known about the dietary habits of many of the cultural subgroups in the United States.”
  • The Report acknowledges that “more data are needed on dietary intake of older adults.”
  • The Report acknowledges that current data is insufficient to “properly evaluate the status and trends in food and nutrient intake in pregnant women.
  • The Report acknowledges that “insufficient research is being devoted to children and how diseases may evolve over time.”

Sustainability: As uncertain as the science behind diet and chronic disease relationships is, the science regarding sustainable agricultural practices is even more so. The evidence on this issue is in initial stages of development.  As it progresses, it will require experts in agricultural and environmental sciences, rather than nutrition, to evaluate it.

Conclusion: The era of controversial and unsuccessful dietary recommendations must come to an end. As our nation confronts soaring medical costs and declining health, we can no longer afford to perpetuate guidelines that have failed to fulfill their purpose. Until and unless better scientific support is secured for recommendations regarding the prevention of chronic disease, public health nutrition policy recommendations must proceed with restraint and caution.