WASHINGTON - Families victimized by tainted spinach and peanut butter put a human face Tuesday on a recent string of high-profile outbreaks of foodborne illness, urging U.S. lawmakers to strengthen federal oversight of the nation's food supply.

"I can't protect them from spinach -- only you guys can. I can't," said Michael Armstrong, as he and wife, Elizabeth, cradled daughters Ashley, 3, and Isabella, 5.

The two girls fell ill -- Ashley gravely -- in September after eating a salad made with a triple-washed bag of the leafy greens contaminated by E. coli.

That and other incidents of contamination have raised questions not only about the U.S. food supply but efforts by the Food and Drug Administration and other government agencies to keep it safe.

"I hope these hearings will help alert the American people, Congress and the administration to the seriousness of this issue. If it is not taken seriously, these kinds of poisonings can, and will, happen again. Food poisonings will happen to you, to me and to our children and our pets," said Rep. Bart Stupak, D-Mich., chairman of the House Energy and Commerce subcommittee on oversight and investigations. "The American people expect and deserve better from its government."

Also testifying was Gary Pruden, whose 11-year-old son Sean was seriously sickened in November by E. coli after eating at a Taco Bell restaurant. Pruden said a key element of trade and commerce is trust -- whether placed in accountants, airline pilots or auto mechanics.

"That is also extended to the trust in the food we order or buy from the grocery store -- that it's edible and safe. Without that trust, commerce cannot work. And where failure occurs, oversight is required," Pruden told the subcommittee.

The safety of food raised domestically was questioned anew last fall when officials traced a nationwide E. coli outbreak to contaminated spinach processed by Natural Selection Foods LLC. Three people died and nearly 200 others were sickened.

Testing put in place by the company since the outbreak has found 35 lots of spinach contaminated by E. coli, said Stupak, suggesting the problem is ongoing. Company president Charles Sweat later corrected Stupak to say despite those initial positive results, testing of finished spinach and other leafy green products did not find E. coli or salmonella.

"I don't know what the right answer is, but I do know what the wrong answer is: It is to continue doing what we're doing, when it's not working," Michael Armstrong later told Stupak when asked how the food safety system should be changed.

The popular Peter Pan brand of peanut butter was the subject of a nationwide recall in February after a salmonella outbreak. More than 400 people were sickened, and the recall cost manufacturer ConAgra Foods Inc. between $50 million and $60 million.

Terri Marshall said her mother-in-law, Mora Lou Marshall, has been hospitalized or in a nursing home since early January, after she became seriously ill from eating Peter Pan. The elder Marshall, 85, had kept a jar of the peanut butter on her nightstand to supplement her diet -- and had unwittingly continued to eat it, even after she fell ill.

"The very food she thought would improve her health had begun to ravage her body," Terri Marshall said.

Pet food has also had its problems. In March, Menu Foods recalled 60 million cans of dog and cat food after the deaths of 16 pets, mostly cats, that had eaten products contaminated with the chemical melamine. Other companies have since recalled pet foods also tainted by melamine, mixed in with ingredients imported from China.

Rep. Joe Barton, R-Texas, called on the Chinese to allow FDA inspectors visit the plants where the tainted ingredients were made. The agency has awaited letters from the government needed to obtain visas for its inspectors.

"My message, and I think the message of this subcommittee on a bipartisan basis, to the Chinese government is plain: stop these shenanigans," Barton said.

Later, Sweat, joined by officials from ConAgra, Menu Foods and importer ChemNutra Inc., expressed their sympathy, sadness, sorry and support for victims of the outbreaks.

"I don't see the latest string of incidents as aberrations. It's become a systemic problem and it calls for systemic solutions," said Rep. Diana DeGette, D-Colo. Degette has introduced legislation that would give the FDA and Agriculture Department the authority to mandate recalls.