About five and a half years ago, a Yarmouth allergist suggested to writer Caitlin Shetterly that her collection of chronic health concerns – rashes, digestive issues, a constant head cold and perhaps worst of all, inexplicable body aches and pain – might be symptoms of an allergic response to the proteins in genetically modified corn. That is, the proteins that make the corn both pest-resistant and able to survive glyphosate, the pesticide sprayed to kill weeds.

She was dubious but also fairly close to desperate. She’d spent three and a half years sick and searching for solutions. Batteries of tests at Massachusetts General Hospital had yielded no answers. Her toddler had similar health problems, so she went cold turkey. No more corn for her entire family.

Cutting corn from an American diet is even trickier than trying to separate teenagers from smartphones. Corn is everywhere, and most corn grown in America (90 percent) is from genetically modified seeds. As Shetterly puts it in her new book, “Modified: GMOs and the Threat to Our Food, Our Land, Our Future,” it was her “Waldo, popping up everywhere” as an ingredient, even when it wasn’t clearly labeled as such (like, say, dextrose, a sweetener derived from corn).

To avoid corn, she and her husband, Dan, became hard-core farmers market shoppers and dedicated supporters of CSAs. They baked their own bread, canned their own food, ate a diet that was 100 percent organic and 85 percent locally sourced.

Shetterly felt better. Her son felt better. She could hardly believe her luck.

Yet here she is, on a hot morning in late August, standing in a cornfield at a Brunswick farm not far from the town where she lives. Corn has been the seeming bane of her existence. The only corn she has knowingly consumed in years is that grown by farmer friends up the coast, who swear their fields are 60 miles from any GMO corn fields, too isolated to be tainted by the genetically modified corn seed sold by Big Ag giant Monsanto. But Shetterly was not only game for being interviewed in this location, she suggested it.

It’s logical though, because her relationship with corn is neither black nor white. She believes, but can’t be dead certain based on the available science, that she was and is allergic to the GMO corn. When Shetterly waded, journalistically speaking, into the highly controversial topic of genetically modified foods, she found it full of gray areas, reflective of “the squishy gray nuance of me.” Whether she was riding a tractor in Nebraska with a young farmer who swore by the GMO corn he grew or visiting the founders of the anti-GMO group Food Democracy Now!, there were no easy, obvious villains or heroes.

“Look at those beautiful tassels,” Shetterly says as she gazes skyward. Her toenails are painted yellow, the very yellow of a kernel of good corn.

TABLE TO BOOK

“Modified” won’t be released until Sept. 20, but it’s already garnered glowing blurbs from fellow Maine writers, including Kate Christensen, Lily King and Michael Paterniti, as well as bestselling Vermont writer Bill McKibben. Both Library Journal and Publisher’s Weekly gave it starred reviews, and it’s on Publisher’s Weekly’s most anticipated fall books list.

Five and a half years ago, it started simply as notes to herself. She’d filled a journal labeled “Sic(k)” (writer humor) with her thoughts and questions about her illness. At the time she wasn’t looking for a new book topic. Her memoir, “Made for You and Me: Going West, Going Broke, Finding Home,” had just come out, and she was digging into writing a “domestic” novel she was excited about. But the diagnosis she’d received from Dr. Paris Mansmann, and her resulting food “cure” was an intriguing story, and she kept going, trying to learn more. She writes in “Modified” that she had known somewhere in “the crunchy granola part of my brain that ‘GMO’ was a term to regard suspiciously,” but she didn’t know exactly why. That’s common for those who distrust GMOs; marrying the genes of a salmon and a tomato seems too weird to be safe.

Her research led to a first-person story in Elle Magazine, published in August of 2013, which ignited a controversy. Shetterly found herself instantly under attack. One of her most vocal critics was Jon Entine, a self-described contrarian and a senior fellow at the World Food Center Institute for Food and Agricultural Literacy at the University of California-Davis. He questioned both her premise and her integrity in a piece for Slate, even quoting one of her sources calling the article “ridiculous.” A week later Entine was back, writing this time on Forbes.com that the Elle story had been “shoddy and misleading” and accusing her of setting out to “evangelize her experience of salvation.”

But with the controversy came attention from the publishing industry. Shetterly’s experience might have represented the extreme of questions being asked about genetically engineered seeds and Monsanto, the chemical company that invented glyphosate and made most of the important breakthroughs in GMOS, but it also represented anxieties and suspicions of people nearly everywhere. Keep in mind that since the spring of 2013, anti-GMO activists have held regular March Against Monsanto rallies all around the world.

It was a “completely surreal” time, Shetterly said. “I was thinking, I don’t even want to do this.”

But also that she had to.

“I started to peer into this closet, really wanting to work on my novel, and I was like, oh (expletive) this is like a story that has got all sorts of different angles and meandering paths and lies,” she said. “On both sides.” The temptation to slam the closet door shut was high. But the desire to throw it open was greater.

NO SMOKING GUN

She interviewed editors and/or marketing teams with eight publishers. Most wanted to push her toward writing “the most inflammatory thing, the thing that was going to make the biggest headlines. They didn’t want a discovery. They wanted a smoking gun.”

But Shetterly couldn’t promise that. Maybe, she thought, the diagnosis of an allergic response to GMO corn was wrong, and she’d pulled through her illness while eating a very healthy diet. She warned the editors she had to be open to all possibilities.

“I may discover that GMOs are fine or I may discover that there is something else about GMOs that I don’t like that has nothing to do with me personally,” she said.

Caitlin Shetterly contemplates corn in a Freeport cornfield. Derek Davis/staff Photographer

Caitlin Shetterly contemplates corn in a Freeport cornfield. Derek Davis/staff Photographer Derek Davis/staff Photographer

Kerri Kolen, executive editor at G.P. Putnam, was fine with ambiguity. “She said, ‘This is why I want this: I want you to be open. I want you to look at both sides.’ ” Kolen didn’t require a neat bow on the story – a good thing, since Shetterly didn’t put one there.

“Off the bat, I fell in love with Caitlin’s writing and was drawn to the fact that she was able to take a topic like this that is so very complex and write about it with easy and beautiful prose,” Kolen wrote in an email. “Readers and consumers of food desperately need more unfiltered and practical information about this topic and I do think that ultimately, that becomes our collective agenda in writing and publishing this book – to not only provide a framework for the basic and underlying information but to underscore the need for transparency when it comes to gathering that information.”

In the end, “Modified” does end with uncertainty, scientifically. Shetterly lists off the reasons for her suspicions of GMOs, including the lack of independent studies and animal testing that is available to the public and then writes “…I feel confident that most GMOs are probably dangerous.” Of her own health, she said, “I have come to believe that it is likely GMOs do disrupt our immune systems…” Note the “probably” and “believe” and “likely” – these aren’t certainties.

And they can’t be. The science isn’t there. It’s about hunches. In the book, Shetterly interviews a scientist named Simon Hogan who ran a study on genetically modified peas that showed the peas triggering immune responses in mice. She describes Hogan’s “as still the only sound study out there I know of that indicates a possible danger with GMOs.” But even Hogan is dealing in uncertainties. He tells her he believes “that evidence is probably there,” but it hasn’t been found yet.

SPLENDOR IN THE GRASS

Shetterly has brought a breakfast picnic to the interview. This is not a complete ploy to ingratiate herself with a journalist (although her wild blueberry hand pie is seductive). It’s practical; she can’t eat out easily because of her dietary restrictions. Although she doesn’t know for sure that an allergy to GMO corn caused her problems, she also doesn’t know that it didn’t. So she’s full steam ahead with the diet. But the picnic is a handy means of answering the questions about what she can and does eat. There’s olive oil on a green pepper from her own garden, Maine sea salt, that hand pie, some tomatoes, local cheese, gluten-free crackers and a thermos of tea.

Not long after setting the picnic out, Shetterly spots the farmer who owns the field. He’s pulling out of his driveway and she walks over to greet him. They talk for a few minutes and she comes back, laughing. She says she’d told him that she’s going to bring him a copy of “Modified,” and he asked if he’d still like her after he read it. They talked Trump and Clinton and yet managed to shake hands.

In the pages of “Modified,” you’ll see Shetterly having these kinds of interactions with people of widely varied viewpoints. She visits one beekeeper in Munich and another in Portland. She harvests potatoes with Jim Gerritsen, Maine’s most famous opponent of GMOs, in Aroostook County. Then there’s Zach Hunnicutt, a young farmer in Nebraska. He grew GMO corn and popcorn and had taken to Twitter to help correct the modern-day vision of what a farmer is, specifically what a GMO farmer is; Shetterly goes to see him on the farm. She then takes a detour to interview Richard Goodman, a former Monsanto scientist whom she quoted in her Elle piece. (Goodman condemned it as “just ridiculous” to Entine.) This week, Goodman said by email that he plans on reading “Modified” and continued talking to her after the Elle piece because “I try to talk to anyone who will listen and seems interested.”

She’s by no means fearless – she shares her anxieties about exposing herself to Karen Silkwood-style harm throughout the book – but these potentially awkward encounters were essential to her mission to be fair and balanced.

About that. Did she hear the voices of critics in her head? Were they perhaps even helpful in some way?

“Here is the good and bad thing about me,” Shetterly said. “I am terrible on social media. I’m not at all interested, and I just don’t have time. I mean here I am, raising two children (her younger son was born just as she was sending in her first draft of “Modified”), making most of our food from scratch. We have an old money pit of a house …” Friends and family protected her from the worst of it.

“I knew those voices were there, but you know what?” she said. “All it made me do was work harder to tell the truth, to be open, to be honest and to look at the nuance, to look at the gray area. And to be fair, to someone like Zach? If I was going to go into this, hell bent on my position, Zach and I wouldn’t have even liked each other. I had to know that there were people out there that would dismantle every damn thing I said.”

Her most vocal and vociferous critic, Jon Entine, declined to be interviewed for this article. Writing in an email he said, “I feel for her but she’s misguided,” but that he did not want to be part of publicizing “distortions about science.”

JUST THE FACTS?

Coming under critical fire also made Shetterly an obsessive fact checker. She said six months were devoted to the process, and she hired an independent contractor to help in addition to Putnam’s staff. “We’ve been making changes all summer,” she said. “We even went to a fourth pass.” (Typically an author gets a first pass on an early, bound version of her already edited manuscript. After changes are made in it, “the first pass,” then you’re done.)

But the last-minute changes weren’t just about checking her work. The GMO landscape is changing constantly. For instance, a GMO labeling law passed in July, negating Maine’s 2014 law about labeling foods that contained genetically modified ingredients. (Maine’s law never went into effect because it depended on other states passing similar laws.) That piece of news, which has done nothing to settle the GMO debate because many food activists found the new law too protective of manufacturers, did not make it into the book. Shetterly was still worrying about a tidbit about GMO presence in Africa during the picnic lunch, even though the finished book was already being boxed up and sent out.

GMOs are a hard topic to cover. Emotions run high on both sides of the argument, and the science needs to be explained over and over, yet it remains hard for many to grasp. (Like, they really use a gun to shoot DNA into plant material? Yes.) It’s both controversial and dry. As a counterpoint, Shetterly deliberately kept her tone light, and self-deprecating in places, and included drawings she’d made of yes, that gun, as well as woodcuts by her husband, Dan. There’s even a sketch of a corn borer, the pest that set the GMO wheels turning in many ways, on the back pages, done by her older son, now 7. It’s charming. Much of the book is charming. But Shetterly hopes it’s also ruthless.

Two of the scientists she meets in the book have done controversial research, one a scientist from the University of California Berkeley named Ignacio Chapela, who published a paper connecting GMO corn from the United States with the contamination of Mexican landrace corn. Shetterly says she held Chapela’s feet particularly close to the fire.

“I had to check him backwards and forwards,” she said. “People have said they were surprised (reading this) that I was as ruthless with the anti-GMO people as I was. But, she continued, “I refuse to be an activist who is just whitewashing this version of this story just to fit my own particular version of dogma.”

Is she an activist?

“I don’t think I am an activist. People are going to say I am.” She paused. It doesn’t, she insists, really matter. Nor will the criticism she’s expecting.

“With my last book, I was so emotionally rocked by a positive or a negative thing,” she said. “I wanted to know what everybody thought of it. But it’s so weird, here I throw myself into this national debate that’s huge, and bizarrely, I have like, no skin in the game. I almost feel so Zen about this.”