Major supermarket chains including Costco, Whole Foods, Acme and Hannaford are selling batches of leafy greens that contain Listeria monocytogenes, Consumer Reports revealed in a bombshell report on Friday.
The nonprofit organization, which regularly publishes its consumer-oriented research, said it tested 284 samples of fresh greens — such as kale, lettuce and spinach — and found the potentially lethal bacteria in six of the samples.
"CR's study represents a snapshot of the market and was not large enough to draw conclusions about the safety of specific brands or retailers," Consumer Reports's health and food editor Trisha Calvo wrote. "But the testing underscores that industry needs to do more to improve the safety of leafy greens."
All of the greens were reportedly purchased between June 3 and June 19 at stores in Connecticut, New Jersey and New York. Calvo said at least one of the six samples was tainted with Listeria monocytogenes — a "triple-washed" Nature's Place Organic Spinach Spring Mix purchased at a Hannaford supermarket — contained a strain that was linked to at least two reported listeriosis cases.
The other products that purportedly had listeria were a head of unbranded, unbagged red leaf lettuce from an Acme location, a bag of spinach from Boskovich Farms purchased at a Costco, a batch of unbagged spinach at a Hannaford branch, another batch of unbagged, Lancaster Farm-branded green kale from a Whole Foods location and a head of unbranded, unbagged green leaf lettuce that was also purchased at a Whole Foods store.
Calvo said Consumer Reports immediately notified the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention upon discovering the bacteria. The organization also shared its results with both the suppliers of the greens and the supermarkets that sold them.
In response to the study, the FDA said it is looking into the data.
"The FDA takes the presence of harmful pathogens in our food supply very seriously and considers the risk to public health when taking action," a spokesperson for the agency said.
On the other hand, some of the retailers and suppliers — namely Hannaford and Boskovich Farms — suggested that there was nothing to be overly concerned about.
"The products identified are long past their sell-by dates and no longer in the stores," Hannaford told Consumer Reports in a statement. "However, through an abundance of caution, we have conducted an additional deep clean of the display case where the bulk spinach was purchased."
RELATED: See a list of the 10 best leafy greens for you:
The 10 Best Leafy Greens
The 10 Best Leafy Greens
Is kale really king, and does iceberg sink when it comes to nutrition? To help you zone in on the heavyweights, we’ve ranked ten greens from healthiest to least healthy based on their nutrient density and suggested ways to eat your fill without resorting to humdrum salads.
Here’s proof that great things come in small packages. Microgreens—which are the underdeveloped greens of vegetables such as kale, arugula, and broccoli that are harvested just one to two weeks after planting—are a treasure trove of vital nutrients. A 2012 study lead by scientists at the U.S. Department of Agriculture found that several varieties of microgreens including cabbage and cilantro contain nutrient levels such as vitamins C and E up to six times greater than those found in the mature plants. During early development, vegetables need a full arsenal of vitamins, minerals, and antioxidants to support their growth, so they’re packed with more of the good stuff. Ranging in flavor from peppery to tangy, use microgreens to punch up salads, soups, and sandwiches.
Eat outside the bowl: Place 1 packed cup microgreens, 1 chopped shallot, 1 minced garlic clove, zest and juice of 1/2 lemon, 1 tablespoon red wine vinegar, and 1/4 teaspoon each salt and pepper in a food processor and pulse until combined. With the machine running, pour in 1/4 cup extra-virgin olive oil through the feed tube and blend until just slightly chunky. Serve this vibrant sauce over fish or chicken.
When it comes to grown-up greens, kale is deserving of its superfood epithet. It absolutely smashes its competitors in terms of lutein, a potent antioxidant shown to protect eyesight, and leads the way with respect to beta-carotene and vitamin C. As a member of the Brassica family along with broccoli and Brussels sprouts, kale also brings sulforaphane to the table, a phytonutrient shown to have cancer-fighting properties. Steaming or sautéing kale will mellow this all-star’s bitter flavor.
Eat outside the bowl: For a power-packed creamy smoothie that doesn’t taste like a salad, combine 1 1/2 cups coconut water, 1 ripe avocado, 4 kale leaves, 1 celery stalk, 1 cup frozen mango cubes, 2 tablespoons ground flaxseed, 1 tablespoon honey, and 1 teaspoon fresh ginger in a blender until smooth.
Perhaps Popeye should have been a nutritionist instead of a sailor. Among the greens, spinach harbors the most folate, and according to a recent American Journal of Epidemiology study, consuming more of this B vitamin helps protect against breast cancer development, likely because folate is needed for proper cell division. Spinach is also tops when it comes to potassium, which is necessary for muscle functioning and to keep blood pressure numbers in a healthy range.
Eat outside the bowl: Cook and drain 1 package whole-wheat penne. Place pasta back into saucepan and toss with 2 cans drained albacore tuna, 3 packed cups baby spinach, 2 cups sliced cherry tomatoes, 1 cup sliced roasted red pepper, and 1/3 cup chopped basil. In a small bowl, whisk together 1/4 cup extra-virgin olive oil, juice of 1/2 lemon, 3 minced garlic cloves, 2 teaspoons Dijon mustard, and 1/4 teaspoon each salt, black pepper, and red chili flakes. Toss dressing with pasta.
As the name implies, these are the lacy-edged leaves of the same plant that produces mustard seeds. Mustard greens tend to be a little less bitter and more peppery tasting than kale or Swiss chard and come second to only kale in beta-carotene. In our bodies, beta-carotene can be converted to vitamin A to bolster eye and bone health. The greens also contain an arsenal of phytonutrients called glucosinolates that can rev up detoxification enzymes to help protect the cells of our liver and other organs from all the nasties of free-radical damage.
Eat outside the bowl: In a large skillet, heat 1 tablespoon oil over medium heat. Add 1 medium chopped onion and cook until soft, about 5 minutes. Add 2 minced garlic cloves and cook 1 minute more. Stir in 1 bunch mustard greens torn into large pieces, 1 tablespoon soy sauce, and 2 teaspoons sesame oil and cook until greens are slightly wilted. Season with salt and pepper and serve as quick side dish.
5. Collard Greens
This Southern favorite has large, leathery leaves and a somewhat mild flavor, but its tough texture calls for longer cooking times than other greens. On top of providing a payload of vitamin K, vitamin C, and beta-carotene, collards contain higher amounts of dietary fiber than other leafy greens. A 2012 Swedish study found that women who ate the most fiber had almost a 25 percent lower risk of suffering heart disease than those who consumed the least.
Eat outside the bowl: In a large pot of boiling water, blanch 1 bunch collard greens until tender, about 5 minutes. Chop greens and toss with 2 cups cooked quinoa, 2 cups diced cooked chicken, 1/2 cup chopped parsley, 1/3 cup sliced sun dried tomatoes, and 2 tablespoons extra-virgin olive oil.
6. Swiss Chard
There are two primary varieties of Swiss chard in markets: one with multi-colored stems and veins, called rainbow chard, and another with white stems and veins. Both types have a slightly bitter taste that wanes once cooked. Among chard’s many nutritional highlights is more vitamin K than any other green—three times the daily quota in a mere cup serving. On top of its role in proper blood clotting, vitamin K helps fortify bone strength and Dutch researchers recently determined that high intakes can slash the risk for type 2 diabetes by improving insulin sensitivity.
Eat outside the bowl: To up the health ante at snack time, make a batch of Swiss chard chips. Preheat oven to 350 degress. Tear 1 bunch Swiss chard leaves into fairly large pieces and toss with 1 tablespoon oil, 1 teaspoon garlic powder, 1/2 teaspoon smoked paprika, and 1/4 teaspoon salt. Place leaves on two baking sheets (or prepare in batches) and bake until crispy, about 15 minutes, being careful not to burn leaves.
Arugula has a pungent, peppery flavor that has worked its way into the recipes of many rock star chefs. You’ll most often find it at the grocery store in plastic containers alongside baby spinach. Vegans, those lactose-intolerant, and anyone who doesn’t like milk should note that arugula is a surprisingly good source of calcium—it has more of this bone-builder than the other greens on this list. Loading up on arugula may also help you breeze through your workouts since it has high levels of natural nitrates—what your body uses to nitric oxide, which increases muscle blood flow—that Swedish scientists found can help your muscles work more efficiently during exercise.
Eat outside the bowl: For a riff on pesto, place 2 cups arugula, 1/2 cup basil, 3 chopped garlic cloves, and 1/3 cup walnuts into a food processor and pulse a few times, until coarsely minced. Add 1/2 cup grated Parmesan or Parmigiano Reggiano, juice of 1/2 lemon, and 1/4 teaspoon salt and process until combined. Scrap sides of bowl. With machine running, pour in 1/4 cup olive or walnut oil and mix until fully combined. Use on burgers, sandwiches, or pasta.
If darker greens are too bitter to swallow, try this crispy lettuce. The medley of nutrients romaine provides includes beta-carotene, folate, potassium, and vitamin C. Science shows that women who consume higher amounts of vitamin C have healthier blood pressure numbers. Heads of romaine tend to be more perishable than heartier greens, though, so store them in the refrigerator wrapped in a damp paper towel for up to three days.
Eat outside the bowl: In a large saucepan, heat 1 tablespoon oil over medium heat. Add 1 large chopped yellow onion and cook until soft and translucent. Add 2 chopped garlic cloves and cook for 1 minute. Add 5 cups low-sodium vegetable broth, 2 peeled and chopped potatoes, 1 teaspoon dried thyme, and 1/4 teaspoon each salt and black pepper. Bring to a boil, reduce heat, and simmer for 15 minutes. Chop 1 head romaine lettuce and add to mixture with 1 cup frozen peas. Continue simmering until all the vegetables are tender. Stir in 1 tablespoon red wine vinegar and puree with an immersion blender (or in batches in a blender) until smooth. Serve soup topped with low-fat sour cream.
9. Boston (Butterhead)
Resembling a blooming rose with deliciously tender light green leaves, many people find eating raw Boston lettuce more appetizing than the robust darker greens. Swap out your carby tortillas or flatbreads for the large, pliable leaves when making wraps for a good dose of vitamin K and manganese, a mineral necessary for proper carbohydrate and protein metabolism. And like other greens, this leafy green is exceptionally low-cal—a cup will set you back a mere seven calories.
Eat outside the bowl: In a bowl, whisk together 1/2 cup plain low-fat yogurt, juice of 1/2 lemon, 1 teaspoon curry powder, and 1/8 teaspoon cayenne. In another bowl, stir together 2 cans drained and flaked salmon, 1 can rinsed and drained navy beans, and 1 cup grated carrot. Place some salmon mixture on a Boston lettuce leaf and top with a few dollops of curry yogurt. Repeat with remaining ingredients.
One of American’s favorite vegetables is far from nutritional nirvana. Made up mostly of water, iceberg lettuce pales, so to speak, in comparison to darker greens in terms of vitamins, minerals, and disease-busting antioxidants. Still, with just 10 calories in a shredded cup, it won’t do any harm to your beach body and its toothsome crunch can enliven sandwiches, tacos, and mixed green salads.
Eat outside the bowl: Serve breakfast tacos by mashing three hard-boiled eggs in a large bowl and stirring in 1 cup black beans, 1 diced plum tomato, 1/2 cup diced red bell pepper, 1/2 teaspoon paprika, and 1/4 teaspoon salt. In a small bowl, mash together 1/2 ripe avocado with juice of 1/2 lime. Spread avocado mixture on small corn or whole-wheat tortillas and top with egg mixture and shredded iceberg lettuce.
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Boskovich Farms, for its part, said that inspections at its facility did not show any evidence of contamination.
Listeria monocytogenes can lead to listeriosis, an illness that mostly affects pregnant women, the elderly and people with weakened immune systems, according to the CDC. Symptoms of the sickness include fatigue, headaches, loss of balance and convulsions.
Consumer Reports suggests that consumers "stick with leafy greens that you cook."
"If you cook greens until they are fully wilted, they're likely to have been heated enough to be safe," said James E. Rogers, the organization's director of food safety research and testing.