Are onions safe to eat after the E. coli outbreak? What you must know

The Centers for Disease Control and Prevention (CDC) confirmed last month that slivered onions served on McDonald's Quarter Pounder hamburgers were the probable source of an E. coli outbreak that prompted the fast-food restaurant chain to stop selling the menu item temporarily.

At least 104 individuals in 14 states fell ill, and there was one death reported in Colorado, according to a CDC statement. But, per the CDC, the real number of people who became sick from this E. coli outbreak is likely higher.

Because the onions from the supplier were recalled and are no longer available for sale to food service operators, it's not necessary to avoid eating onions or other foods made with onions, the CDC said.

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But should you be concerned in general about eating onions?

The CDC said it's not likely the recalled onions went to grocery stores or directly to consumers. 

"When people are selecting onions at the grocery store, my advice is to look for onions without cuts or other obvious blemishes," said Donald W. Schaffner, a professor and chair of the Department of Food Science at Rutgers University in New Jersey. 

"Places where produce items like onions are damaged can represent sites for microbial growth and can lead to spoilage or, if pathogens are present, multiplication to higher levels [can be] riskier."

Like many fresh produce items, onions can become contaminated with E. coli if they are exposed to contaminated water or soil during growing, harvesting or processing, said Sarah Heckler, a registered dietitian with Anne Till Nutrition Group in Raleigh, North Carolina. 

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Contamination may also occur if onions are handled by people with unclean hands or if the food encounters dirty surfaces, Heckler told Fox News Digital. 

Onions remain a healthy and versatile food, Heckler said.

They provide essential vitamins like C and B6, minerals such as potassium and manganese, and dietary fiber for gut health. 

Plus, with their low-calorie count and high antioxidant content, onions can reduce inflammation, support immunity and lower the risk of chronic diseases, Heckler said, making them a flavorful and nutritious addition to your diet. 

Cooking onions to an internal temperature of 165 degrees Fahrenheit kills E. coli and other harmful bacteria, Heckler said — making cooked onions safer to eat. 

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"If you're concerned about contamination, cooking is an effective precaution," she said.

There are a few tips to know to avoid contamination. 

"When purchasing raw onions, look for firm onions that show no signs of damage and then store them in a cool, dry place," recommended Erin Palinski-Wade, a registered dietitian in Sparta, New Jersey, and author of the book "Walking the Weight Off for Dummies." 

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Wash your hands before and after handling an onion, Palinski-Wade said. 

Before preparing a raw onion, rinse it under cold water, she also advised.

During the holidays, when multiple people are in the kitchen prepping food together, there is a higher risk of cross-contamination, Palinksi-Wade told Fox News Digital. 

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"And with the business of the holidays, it is more likely food may be left out at unsafe temperatures or not stored properly," she said. 

To help minimize the risk, she suggested designating a food prep area specifically for raw produce that is kept away from raw meats and other possible contaminants.