In the early 1990s, shopping for tomatoes usually meant buying one of those big, pale-red beefsteaks. If you were lucky, you might come across plum-shaped Romas or perhaps some cherry tomatoes. Nowadays, walk into most grocery stores during any season and you’ll find a sea of options: round reds of all sizes; grape tomatoes; heirloom varieties in yellow, green, brown, and purple; little orange Sun Golds, and, yes, a few beefsteaks. While the proliferation of tomatoes has been marked, supermarkets now stock a wider array of produce than they did 20 years ago.

The display of oblong, fluted, and wildly colored tomatoes looks more like a farmers market stall than what you’d expect for a supermarket. It’s a shift that’s usually chalked up to changing tastes and an interest in healthier eating. What often gets overlooked, however, is the impact of the North American Free Trade Agreement on the American diet.

Signed in 1994, NAFTA boosted trade between the United States, Canada, and Mexico by stripping away most tariffs on a wide range of goods, letting products flow freely across the borders—including a lot of food. According to the Department of Agriculture, since NAFTA’s inception, Americans eat twice as much fruit and three times as many vegetables from Mexico and Canada. As of 2012, America spent more than $33 billion on agricultural imports from the two countries. Before NAFTA, that number was about $6 billion.

Every day, hundreds of trucks shuttle greenhouse tomatoes, peppers, and cucumbers down from Canada and fruit and vegetables like papaya, bananas, and avocados up from Mexico. When the question of food miles—how far a morsel travels before it gets to the table—arose in the early 2000s, it was easy to think such long journeys had always been the norm. But relatively recent free -trade agreements, starting with NAFTA, are what have made feasible this extensive food import-export web and its effect on American eating habits.

Since 1994, the United States has inked a dozen similar deals with countries as far away as Australia and South Korea, including a NATFA-like pact with a clutch of Central American countries. Many of these have brought more new food to American tables. Forging ahead, the U.S. trade representative is currently in negotiations on the Trans-Pacific Partnership, a free-trade deal among Pacific Rim countries. Just last week, Congress granted President Obama the authority to fast-track the negotiations—and largely with Republican votes—meaning that the House and Senate will only have the opportunity to approve or reject the finalized deal. It would be the largest free-trade pact in history, involving 11 other countries, from Chile to Japan, representing almost 800 million people and accounting for 40 percent of the world economy. (Some of these countries already have such compacts with the United States; the TPP would supersede those rules.) This latest agreement is again expected to impact what Americans eat, making certain foods more accessible, but also, critics warn, threatening hard-won domestic health and safety protections.

Free Trade’s Menu

Prior to NAFTA, grocery stores sold mostly domestic produce, except during the bleak winter months. Only then, after shoppers had gobbled up the harvest from places like California and Florida, did the federal government ease its steep tariffs on imports. When the taxes were in force, those fees stifled cross-border trade—the levy on asparagus, for example, was 25 percent. In one stroke, NAFTA did away with these fees, opening the huge U.S. market to Mexican and Canadian growers all year long. Consequently, produce became more affordable and accessible to Americans, and this new trade normalized the shipping of fresh food to ever-more-distant locations. Today, the average morsel travels 1,500 miles to get to the table.

It wasn’t that long ago that all the food we ate in the United States was grown here. What we’ve done is turned food into a commodity, and, with that, we’ve come to take it for granted. Mark Kastel, Cornucopia Institute

NAFTA led to greater investments in farms north and south of U.S. borders. It also created an incentive for growers in those countries, as well as domestically, to differentiate themselves by trying new seeds—hence the plethora of tomatoes. “It makes a big difference if your market is a much larger one that’s year-round,” said Kathy Means, vice president of industry relations at the Produce Marketing Association, the sector’s primary trade group. “That lets you really make a business plan that includes taking risks with new varieties—you don’t just have to stick with the tried-and-true.”

While imports from Canada have increased, those from Mexico have exploded. Since NAFTA’s signing, according to the USDA, the volume of produce the United States gets from its southern neighbor has tripled. Consider watermelon: Before NAFTA, only 5 percent of what Americans ate came from Mexico; in 2010–2012 that number was 20 percent. Before NAFTA, the United States sourced zero avocados from Mexico; now almost 50 percent come from south of the border. Since the early 1990s, consumption of Mexican strawberries has increased fivefold. (The latest USDA data shows that, trumping all produce, the number-one single agricultural import from Mexico is beer—apparently the USDA, like partying college students, counts beer as food.)

Fueled by this export boom, agricultural development in Mexico took off. And with the proliferation of fresh fruits and vegetables has come harsh labor conditions for many farmworkers. A 2014 Los Angeles Times investigation found extreme conditions in which some farms essentially held laborers captive, withholding pay, deploying guards, and coercing them to work.

With each new pact signed, more tariffs have been erased for the full range of goods, and more food has come flowing into the United States. The value of imports from Chile grew by 180 percent after that country signed a free-trade deal with the U.S. in 2003. One of the biggest imports from Chile is fruit, particularly grapes and blueberries. Guatemala, a trade partner the Central American Free Trade Agreement, signed in 2011, is now the 16th-largest agricultural supplier to the United States. In 2013, the tiny country sent the U.S. almost $2 billion worth of fresh produce, including cantaloupe, bananas, plantains, and green coffee.

While our food sources and palates have evolved as successive presidents craft new free-trade deals, critics say our food safety and respect for the limits of agriculture have dwindled.

“It wasn’t that long ago that all the food we ate in the United States was grown here,” said Mark Kastel, a senior analyst and cofounder of the Cornucopia Institute, a farm policy research organization. “What we’ve done is turned food into a commodity, and, with that, we’ve come to take it for granted. Americans have very little consciousness of how our food gets to the store.”

Let Them Eat the TPP

As with previous trade agreements, the TPP is being negotiated in secret, so details are scarce. What is known comes from a few passages that have been leaked. Among what’s likely to be included, observers say, is lifting tariffs on seafood imports and pressure to unwind support for locally grown agriculture.

Erasing seafood taxes with signatory countries would trigger an influx of new imports. A lot of the fish would come from Vietnam, which is home to a $5 billion fishing export market that’s increasingly focused on aquaculture. Food safety advocates are wary, because more Vietnamese fish would increase the chance of chemical residues and food-borne illness showing up on American dinner plates. Much of the seafood in Vietnam—including shrimp, crab, catfish, and tilapia—is raised in tightly packed tanks. The use of fungicides, antiparasitics, and steroids to control disease and speed growth in such confined spaces is common. While this is perfectly legal in Vietnam, these substances aren’t allowed in the U.S. food supply. However, even with the knowledge of farming practices such as those used in Vietnam, there is scant inspection at the U.S. border—only 2 percent of fish imports ever get checked.

According to Food & Water Watch, a health and safety nonprofit, between 2008 and 2012, U.S. Food and Drug Administration border inspectors tested 3 percent of Vietnamese seafood imports. The United States imports 90 percent of its seafood, and Vietnam is among the top six trade partners to help meet that demand. Inspectors rejected 18 percent of the fish they tested, which is three times more than the overall food import rejection rate, the organization said.

“When you add all these various free-trade agreements together, you’re getting a lot more product coming in with a lot less inspection,” said Jaydee Hanson, a senior policy analyst at the Center for Food Safety, a citizens’ group that is critical of the TPP. “And that’s what can lead to serious problems.” This is certainly true for fish. According to the Centers for Disease Control and Prevention, of the food-borne-illness outbreaks caused by imports from 2005 to 2010, 44 percent involved seafood—more than any other single type of food.

In addition to possibly further tainting America’s seafood supply, the TPP also could empower signatories and corporations based in those countries to challenge public-procurement buy-local directives across the U.S. These directives stipulate that taxpayer money spent to supply publicly funded facilities, such as schools, hospitals, and universities, be spent on goods that support local economies. As they relate to agriculture, such buy-local policies require some portion of the budget be spent on locally grown food as opposed to imports. This is one of the few victories that farm-to-table sustainable agriculture proponents have secured against agribusiness and a largely unfriendly USDA.

Here’s the logic: To the United States’ free-trade partners, buy-local initiatives can be perceived as barriers to trade. If TPP participants choose to challenge these rules, efforts to connect farmers, eaters, and decision makers could be made obsolete. While the TPP eliminates obstacles to trade for multinational corporations, it may well destabilize burgeoning efforts to foster an environmentally sound food system in the United States.

A trade agreement that puts human and ecological health ahead of the unfettered flow of goods would look very different from the pacts the United States has accumulated in the past two decades. While most of these deals affect the American diet by contributing to more people eating unprocessed vegetables and fruits, critics say what underlies these shifts ultimately erodes the larger good.

“Locally grown programs don’t fit with free-trade agreements,” said Karen Hansen-Kuhn, director of international strategies at the Institute for Agriculture and Trade Policy, a research nonprofit. Similarly, these pacts are incompatible with strong food-safety, labor, and environmental standards for imports. “If our goal was to make our agriculture sustainable,” she said, “then the trade negotiators would not use grassroots gains like buy-local initiatives as bargaining chips.”