Michelle Obama may want to try adding some photos to student lunch trays. (KEVIN LAMARQUE/REUTERS)

University of Minnesota researchers went into local elementary schools where students got to choose among side dishes with their entrees. For two days, they put photographs of carrots and green beans in the compartments of the lunch trays. The photos were meant to indicate what vegetables should go in the compartments.

The intervention was cheap and fast. Putting the photographs on 100 trays took 20 minutes and cost $3. But the results were impressive: The percentage of students who chose green beans more than doubled; number of those who selected carrots grew from 11.6 percent to 36.8 percent.

“Placing photographs in cafeteria trays requires no special training and incurs minimal costs and labor, but was associated with an increase in vegetable consumption within the range of those found in more expensive interventions,” the authors concluded in a research letter in this month’s Journal of the American Medical Association.

These experiment was successful after only two two days in an elementary school, and the authors say more research is needed. But it’s encouraging to see a relatively fast and cheap school food policy showing promise.