The economy has “crystallized the tradeoffs that consumers are willing to make,” she said. “Fair trade is nice, but fair trade may fall off the shopping list where organic milk may not.”

Thomas J. Blischok, president of consulting and innovation for Information Resources, a market-research firm, said shoppers were not moving entirely away from categories like organic products in the grocery store. But they are becoming more selective, buying four or five products instead of seven or eight, he said.

Mr. Blischok conducted a survey of 1,000 consumers in the first half of the year and found that nearly two-thirds said they were cutting back on nonessential groceries and nearly half said they were buying fewer organic products because they were too expensive. Such consumer attitudes have compounded problems for Whole Foods Market, the Austin, Tex., chain that served as a launching pad for many organic and natural brands. The company’s stock has dropped by more than 70 percent since the first of the year, and analysts expect more grim news when fourth-quarter earnings are announced next week.

Recently in Boston, on the sprawling convention floor of the Natural Products Expo East, some vendors said they had been hurt by the economic malaise and others said they had not yet felt the impact.

Several of them noted that Whole Foods Market faces a broad array of problems, including increased competition from traditional grocers, and should not be viewed as a proxy for the whole industry. But many also worried that if the economy continues to flounder, consumers — particularly those who only occasionally shop for their products — may decide they can no longer afford to let their conscience dictate their shopping list.

Theresa Marquez, the chief marketing executive for Organic Valley, which sells primarily dairy products, said she was not worried about core customers because they were so committed to buying organic.