At a panel on food systems at the Food Book Fair in New York City last weekend, nutrition and food expert Marion Nestle proved a force with which to be reckoned. Her co-panelists included Jared Koch, founder of Clean Plates, and Nate Appleman, the celebrated chef who is currently head of the culinary team for Chipotle. The chain has been recognized for their efforts to serve locally-sourced and responsibly grown produce and meat, against the grain of the conventional food system. Moderator Evelyn Kim asked a question which dominated most of the discussion: Can big food corporations do good?

Speaking for Chipotle, Appleman was confident that it can and said that while a lot of companies might claim to do good, Chipotle stands behind that claim by sourcing their food more responsibly.

With a steely gaze and unimpressed attitude, Marion Nestle disagreed. “There is an inherent conflict of interest,” she said of Chipotle and other big food companies. She argued against the large portions of food at Chipotle as evidence. “They are contributing to people’s over-consumption of calories and are stuck in that model. If anything affects their bottom line, they don’t do it,” she said.

Koch brought up the myriad conflicts in supporting good food causes and selling food. He explained his criteria for rating restaurants in Clean Plates, a sort of Zagat survey that judges not by taste but by what measures a food establishment has taken to ensure the sustainable, local, safe, and ethical quality of its food. Apparently speaking for Appleman, Koch said that Chipotle will admit that they’re not perfect in every sense, but that we should try to support companies that are trying to do a better job.

The question of whom to trust to ensure this was being done was the elephant in the room. “We don’t have someone accountable,” Nestle stated. “We have a broken government that can’t even get bills passed,” she said, bringing on one of the only moments of comedy relief for the panel. “The job of food companies is to sell food. They’re not social service agencies. It’s unreasonable to assume them to be social service agencies.” So, according to Nestle, the only way to intervene is through third-party regulation. It was a somber admission of hopelessness, it seemed.

Kim noted that Wal-Mart is currently the largest buyer of organic milk and that buying power can wield big changes “across the board.” But is there enough supply? Right now, Appleman admitted, there’s not enough grass-fed beef to supply Chipotle, hinting at some of those imperfections to their model. But he turned the obstacle into a “when life gives you lemons” argument, explaining that that’s why Chipotle has been buying whole animals and using extra cuts to supply its new Southeast Asian spin-off chain, Shophouse.

It has also slowly begun to roll out an organic tofu offering in some of its Chipotle restaurants. “We started it in seven restaurants, then in 90 restaurants,” he said of the tofu’s menu appearance, in order to test out the water. So that rises the demand for organic soybeans and tofu, Nestle said, nodding.

“You’re on my side now,” Appleman said, incredulous.

But he spoke too soon. Nestle took Chipotle to town for its confusing calorie labeling, whereby a burrito–depending on what you decide to put in it–could contain as few as 300 or as many as 1,200 calories. “That’s not helpful,” she said. When Appleman offered the advantage of customers’ choice in what they could add to their meal, Nestle refused to take the bait. “If it’s the same price when you add everything, who wouldn’t take advantage of that?” she asked.

Let alone identifying potential or actual conflicts of interest in the food industry, there was a true conflict of interests among the panelists. Nestle’s and Koch’s work could be grouped as public awareness advocacy, while Appleman’s or Chipotle’s was to feed, foremost. And feed more and more people year after year. “Why do companies have to grow?” Nestle mused early on in the discussion. “The pressure to grow is responsible for enormous food marketing that I attribute to the rise of obesity–corporations pushing food at all times of the day. I don’t see growth as being a value that everyone should be subscribing to.”

“But what about the “growth” of buying more local food?” Appleman asked.

When questions were taken from the audience, the elephant emerged more than once.

“How do you ensure or enforce those standards with your farms and how easy or difficult is this for other big corporations to follow?” I asked Appleman. Haplessly, Appleman didn’t have an answer. “I’m just in charge of culinary,” he said.

But another audience member had a nearly identical question a few minutes later, to which Appleman threw up his hands and pointed to a colleague in the audience, named Josh, who apparently handled those things at Chipotle. Josh rose and gave a two-minute elevator speech: “We look directly at every single thing we buy and continue to… it’s quite complex, but we are very reasonably trying to strive for sustainable practices in labor,” he said, not addressing how difficult this was for big corporations to do. He also noted, “We typically are engaging with our suppliers instead of individual farms directly to ensure that they’re following those practices.”

Another audience member spoke up to plug B Corporations, a tool by the non-profit B Labs to certify sustainable and fair business practices. It was news to all the panelists except Koch. Like Clean Plates, the tool’s existence alone is telling of a lack of clear definitions and transparency as to how exactly food companies practice “sustainability.”

Sure, you could have Willie Nelson sing in all the commercials you can buy, and serve up tofu burritos as long as it makes financial sense, but a self-imposed standard of “sustainability” from a fast food chain is bound to carry conflicts and raise many questions. This was the prevailing takeaway from the panel. That, and coupons from Chipotle, which were passed out to all attendees as they left the room–embossed gift cards for buy-one-get-one-free burritos.