Could refrigeration explain Crohn's rise?

The cause of the small-intestinal inflammation called Crohn's disease is a mystery. Researchers in France now hypothesize that the widespread use of refrigeration has permitted certain bacteria to linger longer than other microbes do in food. The hardy bacteria could then cause low-grade infections in the digestive tracks of susceptible people.

Crohn's disease was first diagnosed in 1935. Since genetic mutations linked to the condition crop up in only about 15 percent of patients (SN: 5/26/01, p. 327), many scientists suspect that environmental factors play a part.

Jean-Pierre Hugot of Robert Debre Hospital in Paris and his colleagues point out that in 1937, about half of U.S. families owned refrigerators. Sweden and Britain reached this level later. Correspondingly, Crohn's cases rose in the United States in the 1940s, in Sweden in the 1950s, and in Britain in the 1960s, the authors note in the Dec. 13, 2003 Lancet.

Hugot and his team observe that Yersinia and Listeria, two bacteria that handle chilly temperatures well, routinely survive refrigeration and infect the guts of people who undercook their meats. The scientists cite two modest-size studies that found Yersinia in 63 percent and 31 percent of Crohn's patients tested.

However, these limited data don't establish that the microbes are present in greater numbers than other bacteria are, says Warren Stroher of the National Institute of Allergy and Infections Disease in Bethesda, Md. He also points out that antibiotics--which kill off these bacteria--don't help Crohn's patients.

Moreover, says Gabriel Nunez of the University of Michigan in Ann Arbor, it's not clear what type of bacteria causes Crohn's disease. Thus, the refrigeration hypothesis, he concludes, is highly speculative."