Assessing the Environmental Impacts of Human Diets

By Dr. Timothy Griffin

Dietary guidelines are about diets and health, but the ways people eat have many impacts. The Dietary Guidelines Advisory Committee (DGAC) began its work in late 2013, and released its Scientific Report in February 2015. Along with Dr. Mike Hamm of Michigan State University, I served as an advisor to the DGAC, which for the first time included an assessment of the environmental impacts of human diets.

Much has been made of the fact that the DGAC included these issues (both in support and in opposition), but the rationale for inclusion is clear: our ability to meet food security goals in the future is directly impacted by our use of resources now. Because food security is central to the Dietary Guidelines, sustainability is clearly in the scope of the DGAC.

The work of the DGAC is structured around specific questions. (These questions are answered by the amazing people at the Nutrition Evidence Library!) The two primary sustainability questions that framed that part of the report were not particularly controversial. The first question was: Do different dietary patterns have different impacts? Not surprisingly, the answer is “Yes” (of course). Many reports on this finding implied that people should change their diets for the good of the planet – that may be a good thing in and of itself, but it is not what the DGAC said. The primary point from the DGAC was that dietary changes that have specific, positive nutritional and health outcomes (fewer calories, increased fruit and vegetable consumption) also have positive environmental outcomes. 

Seafood was the topic of the second question, combining sustainability, nutrition, and food safety. The implications of increasing seafood consumption on the viability of wild-caught and farmed seafood were one focus, and the nutritional composition of wild-caught versus farmed products was another. Both of these flow directly from the nutrition advice of previous Dietary Guidelines, regarding the health benefits of consuming more fish and seafood. Other questions and concerns went unaddressed – for example, most fish and seafood consumed in the U.S. (more than 85%) is imported.

The question remains whether sustainability will be included in the 2015 Dietary Guidelines, to be issued later this year (jointly, by Health and Human Services and USDA). Having worked with the DGAC over the last year, and having focused on sustainable agriculture for more than 25 years, I would of course like to see sustainability included. Even so, there is a pressing need to think about the connection between agriculture and nutrition that goes beyond the Dietary Guidelines. We can draw lines in the sand, or we can do the harder work of first talking about the linkage between diets and sustainability, and then developing solutions.

Timothy Griffin, PhD, is Associate Professor and Director Agriculture Food and Environment Program at the Friedman School of Nutrition Science and Policy.