In recent years, as childhood obesity has become a big issue, school cafeteria managers have sought out lower-fat ways to prepare potatoes and food suppliers have scrambled to reformulate their products, Keeling said.
"They're not your daddy's french fries," Keeling said. "They're a different product. A typical serving has 80 to 110 calories."
"The other nasty assumption that USDA makes is that kids are going to eat all this other stuff," Keeling said. "It's only nutrition if kids eat it. … If the dark green leaves end up in the trash can, nobody's better off."
It also irks white-potato growers that sweet potatoes get a pass, even if they are turned into baked fries with the same salt and fat profile of their white counterparts.
Sweet potatoes do contain lots of beta carotene. Keeling said that shouldn't matter because beta carotene has not been labeled a "nutrient of concern," as potassium has. Both sweet and white potatoes are good sources of potassium.
"I'm not trying to slander sweet potatoes, but USDA will allow an unlimited amount of sweet potatoes," he said. "Baked sweet potato fries — they have a halo and we, right now, have horns. They have virtually identical nutritional profiles with exception of beta carotene."
He notes that white potatoes cost 3.4 cents per serving while sweet potatoes cost 37 cents.
"At the same time we're laying off teachers … schools should have the flexibility to deliver nutrition in cost-effective ways," he said.
Weaning school cafeterias off white potatoes is not impossible, even when finances aren't flush. Baltimore City schools have cut back on how often they serve starchy vegetables in recent years, not intentionally but because the district was focused on expanding its food choices, said Mellissa Honeywood, chef/dietitian for city schools.
"Two years ago, we began really reducing our starchy vegetables," she said. "There were fries or tater tots every day."
As the district added new menu items, including all-vegetarian Meatless Mondays, the starchy classics showed up less frequently in the menu rotation.
"We didn't eliminate any item; what we did was expand," Honeywood said.
If adopted, the proposed regulations would still require the district to tweak its menu a bit.
In city elementary schools, starchy vegetables show up three times on the menu for the first week of school, as oven-baked fries, mashed potatoes and corn. One of those would have to go, since each starch is doled out in half-cup servings. The menu for the following two weeks does not exceed the proposed one-cup limit.
"It won't be as dramatic a jump for us," Honeywood said. "If your menu had those starchy vegetables every day, it's going to be a challenge. … With the new regulations, nothing's off the table. You'll just have to … rearrange it."
Her main concern is that schools and students be given enough time to adapt to the changes. Otherwise, she said, they risk turning off students, who might opt to pack a less healthy lunch or eat nothing at all.
"If we make the healthiest food possible and the child doesn't eat it, then we haven't done our job," she said. "The last thing anybody wants is to have a child go hungry or have less healthy snacks."