Live longer? Save the planet? Better diet could nail both

The study, published in the November 12 online edition of Nature by Tilman and graduate student Michael Clark, synthesized data on environmental costs of food production, diet trends, relationships between diet and health, and population growth. Their integrated analysis painted a striking picture of the human and environmental health costs of our current diet trajectory as well as how strategically modifying food choices could reduce not only incidence of type II diabetes, coronary heart disease and other chronic diseases, but global agricultural greenhouse gas emissions and habitat degradation as well.

"We showed that the same dietary changes that can add about a decade to our lives can also prevent massive environmental damage," said Tilman, a professor in the University's College of Biological Sciences and resident fellow at the Institute on the Environment. "In particular, if the world were to adopt variations on three common diets, health would be greatly increased at the same time global greenhouse gas emissions were reduced by an amount equal to the current greenhouse gas emissions of al all cars, trucks, plans trains and ships. In addition, this dietary shift would prevent the destruction of an area of tropical forests and savannas as large as half of the United States."

The researchers found that, as incomes increased between 1961 and 2009, people consumed more meat protein, empty calories and total calories per person. When these trends were combined with forecasts of population growth and income growth for the coming decades, the study predicted that diets in 2050 would contain fewer servings of fruits and vegetables, but about 60 percent more empty calories and 25 to 50 percent more pork, poultry, beef, dairy and eggs -- a suite of changes that would increase of type II diabetes, coronary heart disease and some cancers. Using life-cycle analyses of various food production systems, the study also calculated that, if current trends prevail, these 2050 diets would also lead to an 80 percent increase in global greenhouse gas emissions from food production as well as habitat destruction due to land clearing for agriculture around the world.

The study then compared health impacts of the global omnivorous diet with those reported for traditional Mediterranean, pescatarian and vegetarian diets. Adopting these alternative diets could reduce incidence of type II diabetes by about 25 percent, cancer by about 10 percent and death from heart disease by about 20 percent relative to the omnivore diet. Additionally, the adoption of these or similar alternative diets would prevent most or all of the increased greenhouse gas emissions and habitat destruction that would otherwise be caused by both dietary changes and increased global population.

The authors acknowledged that numerous factors go into diet choice -- but also pointed out that the alternative diets already are part of the lives of countless people around the world. Noting that variations on the diets used in the scenario could potentially show even greater benefit, they concluded that "the evaluation and implementation of dietary solutions to the tightly linked diet-environment-health trilemma is a global challenge, and opportunity, of great environmental and public health importance."