Many folks believe calculating food miles, or the distance food travels from farm to plate, can let them determine the environmental impact of what they're eating. Their thinking – if it's closer to home, it probably emitted less greenhouse gas emissions into the air from transportation than something grown farther away.

But it's not always that simple, according to the Leopold Center for Sustainable Agriculture at Iowa State University. How things are packaged, the methods of production and the mode of transportation all play key roles in the calculation.

For example, it seems that a Maine potato would cause less negative effects on the environment for those on the East Coast than choosing an Idaho potato. But the Maine potatoes are transported in long-haul trucks while Idaho potatoes go by train, a much cleaner mode of travel. So they both actually have similar carbon footprints, even though one originates from much closer to home.

Of course, some prefer more local food because of many other reasons, such as taste or protection against allergies. But for the environment, closer to home is not always better.