Fruits and vegetables can play a vital role in maintaining health. Unfortunately they can also play a part in some uncomfortable illnesses, says a recent doctoral graduate from Texas A&M University in College Station.

"Data from the CDC (Centers for Disease Control and Prevention) indicates that viruses are responsible for most of the foodborne illnesses in the United States," says Everardo Vega, who earned his doctorate degree in food science and technology this month. "Salads and vegetables carry most of these foodborne diseases."

That's why his research focused on how these food items could be so healthful and yet so often be carriers of disease-causing viruses, he says.

Vega studied four viruses: two bacterial viruses often used as surrogates in research done in laboratories, and two animal viruses—echovirus and a feline calicivirus. The former animal virus is a human pathogen that causes many of the viral meningitis cases in the U.S. The latter is not a human pathogen but is related to the Norwalk virus which causes viral gastroenteritis.

Vega wanted to know how these disease-causing viruses attach to fresh produce and how to break that attachment. Vega used lettuce in the study because it has leaves with large surface areas, is grown close to the ground and irrigation water, and is eaten without cooking, which can  kill pathogens, he says.

His research determined that viruses attach to lettuce through electrostatic means. The next step was to find how to break that attachment.

Vega discovered that a detergent developed for use in washing produce was not only ineffective at breaking the electrostatic attachment, but it "actually caused the attachment to strengthen."

However, when sodium chloride—ordinary table salt—was added, the viruses' attachment to the lettuce was broken.

After further testing, Vega found salt alone was just as effective as the detergent with salt added.

The bottom line: Perhaps after more testing is done, food companies may be able to treat lettuce to remove pathogens in a safe, simple way, Vega says. But more research is needed. Studies will need to be done in field conditions, where lettuce is actually growing and being irrigated, he says.