For most of us, the issue of genetically modified food isn’t important enough to write our grocery lists around. While the idea of ingredients that have been scientifically engineered in order to survive diseases and be pest-resistant is hardly appetizing, proponents say they are a way to end world hunger, and there is no solid proof that they can harm us. At the food co-op where I shop, a well-meaning committee affixes green stickers to the shelves beneath non-GMO items, yet if I’m being honest, the labels have little bearing on what I throw in my basket.

At least they didn’t before I read Modified, Caitlin Shetterly’s eye-opening book about an endlessly complicated issue. Shetterly’s interest in the controversial subject comes from a deeply personal place: A mysterious illness that struck when she was in her mid-30s confounded her doctors, who tried all manner of responses—from conducting brain scans to putting her on antidepressants. Finally, after three years of rashes and chronic exhaustion and pain, she saw an allergist and immunologist who suggested she was suffering an autoimmune reaction to genetically modified corn. Though Shetterly was initially skeptical, she eliminated corn from her diet and found herself to be well again.

Filled with a new sense of purpose, she abandoned her plan to write a novel and traveled across America and to Europe in order to speak with the scientists, farmers, and activists on both sides of the genetic modification issue. Modified is her passionate and rather horrifying account of what is happening in the heartland and to our food supply.

GMO corn and soy were first introduced around 1996. In the late ’90s, only 8 percent of corn grown in the U.S. was genetically modified. That number has shot up to more than 90 percent, and the crops that aren’t GMO are still likely to be contaminated due to wind and pollination from birds and bees. At least 80 percent of our packaged food contains ingredients made from GMO corn or soy, as do many natural foods. GMOs are everywhere, from baby food and seven-grain bread to the wax-lined paper cups we pass out at birthday parties.

While there is still little scientific evidence proving the dangers (or safety) of eating foods that have been genetically modified, what’s not up for debate is that the technology allows for widespread use of chemicals meant to protect crops from insects and disease. When you step back and look at the science pertaining to the pesticides that go hand in hand with GMOs, our reliance on engineered seeds becomes harder to shrug off.