"A canned or a frozen green been is going to be the same nutrition as a fresh green bean -- the difference is students tend to prefer fresh because they taste better," he said. "You obviously want students to consume the product."
School districts are also raising lunch prices. On average, Peterson said, schools seem to be raising prices between 15 to 20 cents per student meal.
The suburban New York school district of North Rockland is considering a price increase, but school superintendent Brian Monahan says he worries that more expensive school lunches might prompt parents and students to turn to less healthful alternatives.
"For many families, it takes time as well as money to prepare a lunch. In this day and age, both are in short supply," Monahan said. "We know the school lunches are healthy. We don't know that what students would bring would be healthy."
Like schools, hospitals must also balance rising food costs with nutrition guidelines.
William Notte, the director of food and nutrition services at the University of Florida Shands Hospital, said the hospital cut the size of patients' side salads in half after a food waste study revealed that patients generally don't finish the salads.
Patients wanting more salad can request it, Notte said.
"With the cost being higher, you certainly don't want to be wasting any [food]," he said.
Meanwhile, the price of food sold at the hospital's cafeterias is going up.
Notte said he'll soon implement a 10 percent price increase for cafeteria fare.
For those living in poor neighborhoods, it is just that much harder to get healthy food.
Leslie Mikkelsen, a managing director at Prevention Institute, a non-profit group based in Oakland, Calif., said that some neighborhoods simply don't have a full-service grocery store, and residents lack the financial means to drive the few miles to the nearest store. The smaller stores offer fewer food choices, often at higher prices than supermarkets. Their produce often looks a little wilted and their dairy and meat products might be outdated, she said.
"They might have some fruits and vegetables, but not nearly the variety you would see in a suburban area," Mikkelsen said.
Mikkelsen fears the higher prices could lead to a fatter America, both in urban areas and elsewhere. She said about 40 percent of meals consumed in the United States are from fast food and take-out restaurants. Given the higher prices of groceries, she said it's harder to shift Americans away from those high fat, high sodium foods, toward healthier habits.
Kenneth J. Dalto, a retail analyst who studies supermarkets, said that people who choose to eat at home aren't necessarily eating healthier food.
Dalto said shoppers are buying less meat and vegetables and more breads, potatoes, pasta, rice, frozen fish, frozen pizzas and TV dinners.
"It's lower quality food," Dalto said. "Foods that are prepared, frozen or reheated are of lower quality."
But Jon Hauptman, a partner with Willard Bishop, a retail consulting firm that focuses on groceries, said the biggest change he has seen is a shift to more store brand or generic brand items.
Several big grocery chains have developed their own store brands of natural lines of organic products that "allow consumers to trade down" without changing their diet or food quality.