Earlier this month, the New York Times published a story that discusses the research conducted by professors from NYU and Yale surrounding calorie labels posted in fast food restaurants in poor neighborhoods of New York City. The study concluded that customers actually "ordered slightly more calories than the typical customer had before the labeling law went into effect, in July 2008." As The Atlantic's Marion Nestle argues, perhaps this counterintuitive result is in part due to the fact that many people do not understand calories as a guideline for personal nutrition.

The Swedish National Food Administration took food labeling to the next level this year through their "environmentally effective food choices" program, which includes labels that list carbon dioxide emissions associated with the production of the food product. These labels are now cropping up on menus and some grocery store items. But when the average shopper comes across "Climate declared: .87 kg CO2 per kg of product" on an oatmeal box, is he or she going to understand what that means?

Sure, any person who can count can deduce what the "greener" choice based on these guidelines would be when comparing a handful of menu options. At Max, Sweden's popular hamburger chain, sales of "climate-friendly items" have risen 20 percent since the labels have been introduced. But I find it hard to believe that the public will completely change their shopping habits based on these new labels, especially since "kg CO2 per kg of product" is impossible to visualize and difficult to comprehend.

The CO2 emission labels at Max also have nutritional benefits as they tend to encourage customers to avoid red meat due to the heavy greenhouse gas emissions associated with raising cattle (even though Max is popular for their burgers) and choose leaner options like chicken. But while many environmentally-friendly foods are also nutritious, what happens when carbon emissions and nutritional benefits conflict? For example, fish are rich in health omega 3 fatty acids, but fishing boats burn a large amount of fuel. It is easy to see how this might confuse health-conscious environmentalists--the people who will most likely to scrutinize food labels.

There are also arguments against using CO2 to gauge environmental impact. First, emission on certain foods, like carrots, can vary by a factor of ten. In addition, calculating emissions isn't exactly straightforward. As the New York Times points out, fuel derived from organic sources is treated as if it has no effect on CO2 in the atmosphere, although this is in fact not the case. This creates a serious accounting issue in the creation of the labels. Furthermore, some experts claim that carbon reduction is overrated as climate change strategy, as Steven Levitt and Stephen Dubner write in their controversial new book, SuperFreakonomics.

I think that it is important for the public to be aware of the nutritional content in the foods that they buy and to promote a sustainable food industry. But if a labeling system is going to be established, it is important for them to be accurate and comprehensible. Otherwise, they will be either ignored or misinterpreted, as the study on nutrition labels in New York suggests. I am curious to see how the Swedish system impacts their food industry in the long term, and if other countries will follow.