How risky is it to eat raw oysters? Here's how you can safely consume them, according to experts.

Marine vibrio bacteria, the most common bacteria found in seawater, is often concentrated in oysters.
Marine vibrio bacteria, the most common bacteria found in seawater, is often concentrated in oysters. (Getty Images)

From coast to coast, spanning Connecticut to Florida to Washington state, Food and Drug Administration (FDA) advisories warning against the consumption of raw oysters have been making headlines. Over the past year alone, multiple recalls have been issued because of the potential contamination of oysters with foodborne illnesses such as norovirus, salmonella, and Vibrio parahaemolyticus, one of several strains of vibrio bacteria. Despite the advisories and recalls, oysters continue to be a popular culinary delicacy, not to mention a favorite aphrodisiac. But are they truly as risky as they seem? Yahoo Life reached out to dietitians to explore the complexities surrounding these treasured shellfish.

What are the risks of eating oysters?

Oysters are saltwater bivalve mollusks, known for being filter feeders, meaning that they get their nutrition from extracting algae and other tiny organisms from the water surrounding them. However, as Michelle Rauch, a certified ServSafe food protection manager and registered dietitian for the Actors Fund, tells Yahoo Life, “depending on where and what they are feeding, there is a potential that they could be contaminated with bacteria.” The primary concern with consuming contaminated oysters is exposure to various viruses and bacteria that lead to gastrointestinal symptoms, similar to those of food poisoning.

Marine vibrio bacteria, the most common bacteria found in seawater, is often concentrated in oysters. The Centers for Disease Control and Prevention (CDC) describes symptoms of vibriosis, a vibrio infection characterized by stomach cramping, nausea, vomiting, fever and chills and usually lasts for up to three days after the person is infected.

Recent concerns involve oysters being linked to norovirus, a contagious virus that causes similar symptoms along with muscle aches. “Oysters can carry norovirus if they are harvested from polluted waters or by individuals who are infected with the virus,” explains Rauch. Additionally, oysters remain a common source of hepatitis A, a highly contagious virus that infects the liver.

On top of the risks of foodborne illnesses, Danielle Venhuizen, dietitian and owner of Food Sense Nutrition Counseling, tells Yahoo Life that there’s increasing concern about other contaminants in water sources. Research shows that filter feeders such as oysters, clams and mussels have the potential to accumulate high concentrations of heavy metals in their soft tissues, posing a risk to humans, especially to those who eat oysters more often. Another study found that close to 50% of farmed oysters may be contaminated with microplastics. “While we are still not entirely sure how this affects human health, it’s definitely something to be aware of,” says Venhuizen.

How likely is it that you'll get sick from eating oysters?

According to the CDC, approximately 80,000 Americans per year fall ill from vibrio bacteria, resulting in about 100 deaths annually. Of those, about 52,000 cases are linked to eating food containing vibrio bacteria.

One species of particular concern is Vibrio vulnificus, which is more life-threatening and involves tissue death around wounds. Symptoms include fever, chills, skin redness, blisters, nausea, vomiting, diarrhea and weakness. In severe cases, infected individuals may end up in intensive care, undergo limb amputations or for 1 out of 5 people, the infection can be fatal.

Should you avoid eating oysters?

For healthy adults without any underlying medical conditions, Rauch says the risk of eating raw oysters may be worth it since symptoms of vibrio tend to be mild for that population. However, Taylor Janulewicz, dietitian and owner of My Cancer Dietitian, tells Yahoo Life: “As a cancer dietitian, I strongly advise against raw oysters for anyone with a weakened immune system.” Others that fall under this category include those with liver disease, diabetes, chronic stomach issues, excessive alcohol consumption or abnormal iron metabolism, as well as people undergoing medical treatment that results in a weakened immune system. Older adults ages 65 years and up, pregnant individuals and children under 6 years of age are also considered high risk and should avoid consuming raw or undercooked oysters.

While experts agree precautions need to be taken when eating oysters, they also highlight mollusks' nutritional value. Venhuizen points out that oysters are rich in selenium, iron, calcium, potassium, folate and choline and especially high in immune-boosting zinc. “Adding oysters during the cold months can be a great way to pack in some zinc and ward off those cases of colds and flu,” she adds. Around a 3-ounce serving of raw oysters without the shells has about 5 grams of protein and exceeds daily adult needs for zinc and vitamin B12.

How to safely consume oysters

While the CDC says that most cases of vibriosis occur from May through October when water temperatures are warmer, the risks oysters pose seem to be year-round because of global warming. So what can you do to reduce the risk?

Before enjoying raw oysters, experts advise purchasing them only from reputable suppliers and restaurants that adhere to proper food handling and storage protocols. If you buy oysters for your home, store them in the refrigerator right away to keep them fresh and to minimize bacterial growth. Shuck only oysters whose shells are intact, and make sure to wash them thoroughly to rid of any debris.

Janulewicz also recommends that for immunocompromised individuals, opt for cooked oyster options, like seafood gumbo with oysters, air-fried breaded oysters and oyster stew, to minimize the risk of infection while still enjoying the nutritional benefits.

Cooking oysters properly kills bacteria, like vibrio, says Venhuizen. Kristin Draayer, dietitian and founder of Nutrition by Kristin, tells Yahoo Life: “This means you can still enjoy the high levels of protein and omega-3 fatty acids that oysters offer, but with a much lower risk of getting sick.” Either boil, fry or broil oysters for at least 3 minutes or bake at 450°F for 10 minutes, making sure they reach an internal temperature of 145°F.

Last, Draayer says it’s important to always wash your hands before and after handling oysters (or any food, for that matter), as well as sanitize surfaces, as many viruses can linger on them for an extended period of time.

“Keep in mind that it is almost impossible to tell if an oyster is contaminated by looking at it,” notes Rauch. “It often will not smell or even taste different,” she adds. Following best practices when consuming oysters can help prevent illness. If you suspect you may have symptoms of vibriosis or another foodborne illness, contact your medical provider immediately.

Maxine Yeung is a dietitian and board-certified health and wellness coach.