The fight is on over school nutrition standards that require schools to serve students a half cup of fruits and vegetables at every reimbursable school meal.

A new study offers evidence in support for the rule, but the influential School Nutrition Association wants Congress and the U.S. Department of Agriculture to lift that mandate when child nutrition legislation is reauthorized in 2015.

In a study released in early March, Harvard School of Public Health researchers found the updated school nutrition standards helped boost fruit and vegetable selection in a study of 1,000 kids conducted both before and after new standards took effect in 2012.

Research was conducted in four urban, low-income schools. The study found that after the new regulations, the percentage of students selecting a fruit increased from 52.7% to 75.7%. For students who selected a vegetable, both the percentage consumed (24.9% pre-implementation compared with 41.1% post-implementation) and cups per day consumed (0.13 cups/day compared with 0.31 cups/day) improved, according to a news release about the findings.

Harvard researchers said the updated standards that require schools to serve increased fruits and vegetables did not increase plate waste. Still, the study’s authors said plate waste remains significant, with students throwing away up to 75% of vegetables and 40% of fruits on their trays.

“There is a push from some organizations and lawmakers to weaken the new standards. We hope the findings, which show that students are consuming more fruits and vegetables, will discourage those efforts,” lead author Juliana Cohen, research fellow in the Department of Nutrition at Harvard said in a news release describing the results.

One fresh produce advocate said the study proved the value of the updated standards.

“This study confirms what we are seeing in schools across the country, the new school lunch standards have resulted in students selecting and eating more fresh fruits and vegetables,” Lorelei DiSogra, vice president of nutrition and health for the Washington, D.C.-based United Fresh Produce Association said in a statement. “As the Harvard study concludes, there is no reason for Congress to roll back or weaken the new nutrition standards for school lunch.”

But the study didn’t completely satisfy some critics, who would like to see a broader study of the issue.

“That’s great for the four schools in this one single district,” said Diane Pratt-Heavner, director of media relations for the National Harbor, Md.-based School Nutrition Association. “We are very interested in seeing what the USDA will find in their plate waste study as part of the broader meal cost study they have planned,” she said March 11.

School have been working hard, she said, to encourage students to try all the produce options under the new standards now that schools are offering an even wider variety of fruits and vegetables. Still, some school foodservice officials believe rules must be relaxed.

“We have been hearing from a lot of members who are concerned about plate waste, particularly as a result of the mandate that students take a fruit or vegetable with every meal,” she said. Pratt-Heavner said that is one reason why the SNA is asking the USDA and Congress to lift the mandate that students take a fruit or a vegetable. She said that issue is part of the group’s position paper on child nutrition reauthorization. Pratt-Heavner said the SNA believes that the requirement has led to increased program costs, plate waste, and a decline in student participation.

The national decline in participation rates in the national school lunch is a concern, in addition to higher costs from increased purchases of fruits, vegetables, she aid. Those costs aren’t covered by the 6 cents per meal that school receive for meeting the new standards, she said.

Pratt-Heavner said school officials believe some students, particularly older students, are frustrated they must take a half cup of fruits or vegetables.

“This requirement that if a student just doesn’t want to take a fruit or vegetable, forcing those kids to take a fruit or vegetable. Many of our members are reporting back that is increasing dissatisfaction with school meals,” she said.

Pratt-Heavner said the SNA is not asking for any changes in the standards for school meals; kids would still be offered bigger servings of fruits and vegetables. “We’re just asking for a change in the mandate that students take a fruit or a vegetable with every meal,” he said.

DiSogra said United Fresh supports the requirement that students select a half-cup serving of fruits and vegetables as part of the reimbursable school lunch and/or breakfast.

“Schools around the country have increased the variety of fresh fruits and vegetables they serve, salad bars are an excellent example of this, and students are eating more fruits and vegetables,” she said in an e-mail. “Increasing student’s fruit and vegetable consumption is one of the priorities of the healthier school lunches and breakfast.”