A healthy diet means a healthier you, which also means a healthier planet, right? Well, it’s complicated. 

Eric Roy, of the University of Vermont (UVM), co-authored a study that challenges common perceptions about the link between healthy eating and environmental sustainability. In fact, the research shows that healthy diets can have positive and negative influences on the environment. 

“What we found was that healthier diets are not always more sustainable,” said lead author Zach Conrad of William & Mary. “In fact, in some cases, some healthier diets can increase use of critical resources like water.” 

Conrad, Roy, and co-author Nicole Tichenor Blackstone of Tufts University calculated the resource use of food that is consumed plus all of the food that is wasted at the grocery store and in the home, as well as the inedible parts, like banana peels.

All told, they found that healthier diets are sometimes better for the environment and sometimes worse—it depends on how a healthy diet is defined and which parts of the environment are the focus. 

“Healthier diets tend to have more fruits and vegetables, which don’t require much land but do require a lot of other agricultural resources including irrigation water and pesticides," said Conrad. "And fruits and vegetables are often more perishable than other foods, which means they are wasted in higher amounts." 

“So it’s not just the food itself that is being wasted; it’s all the associated agricultural resources that went into making that food,” said Roy, assistant professor in UVM’s Rubenstein School of Environment and Natural Resources and Department of Civil and Environmental Engineering and fellow in the Gund Institute for Environment.

Their findings, published in Nutrition Journal, could have implications for development of sustainable national dietary guidelines, which would require balancing population-level nutritional needs with the environmental impacts of food choices. 

Using a nationally representative study of over 50,000 Americans, the researchers integrated modeling methods from nutritional epidemiology with food system science to evaluate the linkage between diet quality and environmental sustainability. The goal was to understand the relationship between observed diet quality and the amount of agricultural land, fertilizer nutrients, pesticides, and irrigation water used to produce food. 

The researchers state that improving diet quality while simultaneously reducing environmental impacts is a “global imperative” and “one of society’s most pressing challenges today.” Poor diet quality, the paper states, is now the leading behavioral risk factor for premature death, accounting for over 11 million deaths worldwide. 

Conrad said that generally Americans need to increase their consumption of fruits, vegetables, whole grains, nuts and seeds—and they need to actually eat what they buy. 

“The American public should be advised to reduce their consumption of foods that are high in saturated fat, sodium, and added sugar,” said Conrad. 

“And at the same time, they need to waste less of the foods they purchase,” said Blackstone. 

The researchers chose to focus on the U.S. because poor diet quality is the leading risk factor for premature death and a predominant risk factor for morbidity. Also, the majority of food consumed in the U.S. is produced domestically.

“Thus, shifts in diet quality among Americans would have meaningful implications for environmental sustainability within U.S. borders and beyond,” they write.