A diet that's good for your health is also good for the planet, according to a new study by a group of Cornell University professors.
“In the U.S., nearly 20 percent of all energy goes into the food system,” Pimentel said. “It's almost as much energy as we use in our total automobiles in the U.S.”
Energy use in the food system includes “production, processing, packaging, distribution, preparation and cooking and all that,” Pimentel said.
An example of an energy-wasteful food choice is diet soda. The average American consumes 600 cans of soda a year, Pimentel said. “If you have a diet soda that has one calorie of food energy in it, to produce the carbonated soda that's in the can requires 600 calories of fossil energy,” he said. “And then to put it into an aluminum can is an additional 1,600 calories.
“So that you can drink 1 calorie of diet soda requires 2,200 calories of fossil energy,” he said. “A glass of water is significantly less.”
And better for you. A carbohydrate-conscious diet is not a carbon-conscious diet, according to the study. Consumption of animal protein should be cut by half, Pimentel said. “Production of meat, milk and eggs of course take far more energy than consuming grains or potatoes and so forth,” he said.
On average, Americans eat 112 grams of protein per day, with a little more than 70 grams coming from animal proteins. “That is above what we should be eating, according to the nutritionists. What we should be eating is about half the quantity of meat, milk and eggs that we consume,” Pimentel said.
A vegetarian diet with the same calories as the average American diet requires 33 percent less fossil fuel energy to produce, according to the study. The study does not necessarily advocate for vegetarianism or veganism, Pimentel said. “We provide the data, but it's up to the individual what they want to do,” he said.
Eating locally grown foods as much as possible is definitely better for the environment and often better for your health, Pimentel said. As an example, Pimentel said New Yorkers should consider eating New York cabbage rather than California lettuce. A one-pound head of lettuce contains 50 calories of energy but requires 400 calories to produce in irrigated California. It then takes another 3,000 calories to ship it to New York state, he said.
“So you've got a 50-calorie head of lettuce that now has an investment of nearly 4,000 calories. And it's 95 percent water,” Pimentel said.
New York-grown cabbage also requires 400 calories but doesn't have to be shipped across the country. “And it has more vitamin A, more vitamin C, more protein than lettuce and you can store it all winter long here in New York state,” he said.
“There are things we can do about what we're selecting and what foods we're eating to improve our carbon footprint,” he said.
Pimentel and five co-authors just published the paper in the journal Human Ecology.