CHICAGO - Whole Foods Market said yesterday that it had pulled three popular "gluten-free" products because the items actually contained the substance.

The grocery chain, acting in response to a Chicago Tribune investigation and mounting consumer pressure, also said it would devise a strict definition of "gluten-free" for products sold in its stores and begin monitoring the items so that such problems did not recur.

The Tribune reported last month that its testing showed three Wellshire Kids brand "gluten-free" products sold exclusively at Whole Foods - Dinosaur Shapes Chicken Bites, Chicken Corn Dogs and Beef Corn Dogs - contained between 116 and 2,200 parts per million (ppm) of gluten.

While the federal legal definition of "gluten-free" is imprecise, most experts view "gluten-free" as containing less than 20 ppm.

Gluten - a protein of wheat, rye or barley - can cause allergic reactions for those with wheat allergies and severe abdominal pain for those with celiac disease.

After the Tribune's report, Whole Foods initially balked at removing the products, saying it was the supplier's responsibility to ensure that the items were safe and legal.

But in subsequent days, Whole Foods received about 20 consumer complaints or inquiries, including from people who thought "gluten-free" meant zero gluten, company spokeswoman Libba Letton said.

The chain, based in Austin, Texas, pulled the products nationwide but could not say how many items or how many of its 279 stores were affected.

"Listening to what our customers had to say, in addition to looking at the facts, we decided we just needed to go ahead and pull the products," Letton said.

The gluten-free market has boomed in recent years as stores have sought to attract customers allergic to wheat, those with celiac disease, and parents of autistic children who believe that a gluten-free diet can reduce symptoms.

Whole Foods, for instance, offers store tours of its gluten-free products and operates a dedicated "Gluten-Free Bakehouse" in North Carolina.

The chain said it began pulling the three products about a month after the Tribune's Nov. 21 report. They were made by Wellshire Farms, based in Swedesboro, Gloucester County, whose founder, Louis Colameco, said the family-owned company stopped making the items in June after discovering that the batter coating the food contained gluten.

Still, Wellshire Farms continued to ship the products already in stock to Whole Foods, and the retailer continued to sell them.

Colameco said he was disappointed that Whole Foods decided to pull the products. "But they're the customer," he said. "What are you going to say?"

He said that his firm had found a new batter supplier that could guarantee less than 20 ppm of gluten and that the new products should be back on shelves in a couple of months. Before distributing them, he said, Wellshire will conduct gluten tests throughout the production process.