It must have been something you ate.

“A lot of these people with smaller stores have been doing it secondarily to make money,” says Frank Lampe, editor of the monthly trade magazine Natural Foods Merchandiser. “It was primarily a life-style choice or a mission. But now they’re going up against people for whom money is the primary driving force. It’s going to mean major changes for them.” In the industry, Fresh Fields is widely considered more a profiteer than an evangelist for tofu. And since Whole Foods went public to the tune of a $22 million stock offering in January 1992, it will unquestionably have to pay much closer attention to the bottom line than before.

This has happened before. Have you been to a corner drugstore lately, or do you count on Osco, the people who care? More recently, Barnes & Noble rolled into Chicago and Guild Bookstore rolled up its rugs. Wal-Marts sprout on the carcasses of small-town Main Streets. Osco isn’t a villain, and neither are Barnes & Noble and Wal-Mart. They’re known in the retail world as “category killers”–they sell so much stuff at such good prices that competitors, especially small ones that might have gotten used to a cozy, sleepy market, have to kick themselves in the butt to keep up. Some aren’t that agile.

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“If you believe in promoting sustainable agriculture, if you believe in expanding the awareness that eating whole, natural foods contributes to good health, then you have to see Fresh Fields and Whole Foods as a good thing,” says Dave Goetz, who bought a half interest in Evanston’s Oak Street Market in July, after working there since it opened in 1982. When word arrived that Fresh Fields had signed for a gargantuan space just five blocks from his store and plans to open it this winter, he went on a reconnaissance flight through a Fresh Fields store. “Who I saw in there was mainstream Americans concerned about cholesterol and fat,” he says, “people trying to clean up their act.” Shoppers who initially hit a Fresh Fields or Whole Foods trolling for reduced-fat desserts or breads that don’t spark their wheat allergy might soon turn on to eggs from free-roaming chickens whose beaks aren’t shaved off in gothic factory farms, or to tempeh, a versatile soy-based meat substitute that’s a distant cousin of tofu but doesn’t look like vanilla jello.

Two-thirds of the grocery shoppers in this country say they could eat healthier diets, according to the Food Marketing Institute, a major trade organization that rolls out a cartload of statistics on the industry each year. FMI’s January 1993 survey indicated that 79 percent of shoppers consider pesticide and herbicide residues in their food a serious hazard. That figure is down from a high of 82 percent in 1989, but still nothing for a grocer to sneeze at (one produce-section annoyance the FMI didn’t ask about). Fifty-five percent consider antibiotics and hormones in poultry and livestock a serious hazard, and another 34 percent call them “something of a hazard.” Artificial colorings are feared as either a serious hazard or something of a hazard by 70 percent of shoppers. For two decades natural foods stores of all sizes have aggressively tried to minimize or ban all these evils.

Dominick’s public-relations manager Rich Simpson says their stores near the new arrivals have increased the selection of organic fruits and vegetables and have bumped up mentions of the stuff in local ads. “We introduced organics in the 1980s because we had seen them in other markets and in the health food stores,” Simpson says. “But they haven’t done very well.” The affected stores have also started stocking organic produce loose instead of packaged in Styrofoam and shrink-wrap. “We’ll see if that changes the sales,” Simpson says. “Maybe the customer who wants that kind of produce is thrown off by packaging.”

A spoonful of unrefined sugar helps the herbal medicine go down. By building a store that’s big and full enough to appeal to American consumers’ abundance mentality, by dressing up the food like conventional groceries, and by providing lots of free parking, Whole Foods and Fresh Fields can tap into a vast but so far uncounted reserve of shoppers who’ve wanted to buy healthful groceries but were afraid they’d go home smelling like patchouli. But if they have a similar target, the two big chains have very different histories and management styles.