Summer is the best time for lounging on the beach, enjoying peak seasonal produce, and using any opportunity to dine outdoors. And when we're sipping on a spritz alfresco, it's only natural to want to pair it with a tray of oysters on the half shell. They're the star of every seafood tower and happy hour menu. But they can make many people feel squeamish—understandably so.
Beyond their slimy texture and briny flavor, some skeptics take issue with oysters being served raw. The bivalves are often referred to as nature’s filtration system. A single oyster can filter up to 50 gallons of water a day, which means it can take on the characteristics of its environment.
That's why oysters in the Pacific can taste so different compared to their East Coast counterparts. But as climate change and pollution continue to impact our oceans, that also means oysters can be exposed to some less than savory substances. And since raw oysters aren't exposed to heat, any lingering bacteria and germs will end up in your order, which can cause health problems and even death.
But how serious are these risks, really? We consulted Eliza Whitaker, MS, RDN, Founder and Registered Dietitian at Nourished Nutrition and Fitness, to break down everything you need to know about raw oysters. So next time you order a tray, you can make sure you’re slurping safely this summer.
What Are The Safety Risks Associated With Raw Oysters?
Like with any other raw or undercooked ingredient, oysters come with an inherent risk of foodborne illness. But, in some ways, the dangers are heightened because of the oyster's diet. "Raw oysters are filter-feeding shellfish, drawing in water to get their nutrients, but this also exposes them to bacteria and viruses in the water, which can be concentrated within the oyster," Whitaker says.
Many of the same viruses and bacteria that impact other proteins can be found in contaminated oysters: salmonella, noroviruses, listeria, parasites, and hepatitis A, to name a few. The ways our bodies react to contaminated oysters may vary, but none of them are particularly pleasant. "Symptoms could include vomiting, diarrhea, nausea, and in severe cases, serious illness, especially in those with a weakened immune system," Whitaker says.
But one especially dangerous form of bacteria is becoming a larger risk when it comes to eating oysters. Vibrio vulnificus, which is closely related to the bacteria that causes cholera, is responsible for several oyster-associated deaths in the United States over the past few years.
Health officials consider Vibrio vulnificus infections to be relatively rare, with about 150-200 cases annually. But 20% of people who are exposed to the bacteria die from it, sometimes in just a matter of days. Symptoms range from abdominal cramps and fevers to vomiting. And for those who contract Vibrio vulnificus by swimming with open wounds in contaminated waters, infections may even include necrosis (which is why many refer to the strain as a flesh-eating bacteria).
Vibrio vulnificus has historically been found in warm waters on the Gulf Coast. But it's been steadily proliferating northward along the coasts, thanks to rising water temperatures and extreme weather events. "Rising water temperatures can increase the risk of bacterial growth, especially for Vibrio, which prefers warmer water," Whitaker explains. "Climate change may also impact water quality and pollution levels, which may increase the risk of contracting a foodborne illness when eating raw oysters." The CDC reported that the rate of Vibrio infections has increased eightfold from 1988 to 2018—and about 10% of cases come from eating raw or undercooked shellfish.
How To Reduce Health Risks When Eating Raw Oysters
According to the FDA, the only truly safe way to consume oysters is by cooking them. Thankfully, there are plenty of delicious ways to serve them without exposing yourself to potential foodborne illness, like frying, grilling, or making a batch of oysters Rockefeller. But if you decide to eat uncooked oysters, you assume some level of personal risk. "Even when following best food safety practices, the risk of developing a foodborne illness is not eliminated," Whitaker says.
Those who are pregnant, elderly, or have a compromised immune system are advised to steer clear of raw and undercooked seafood. If you have any doubts, Whitaker says you should consult a medical professional before proceeding. If you're willing and able to assume some risk, you can still minimize exposure to disease-causing bacteria and viruses by eating oysters responsibly.
The best way is to buy and order oysters from reputable purveyors. Businesses that place a lot of care in the harvesting, handling, and serving of oysters are more likely to do their due diligence. It's not a guarantee, but those who are well-versed and knowledgeable about oysters should source them responsibly. Whitaker advises buying oysters that come with a harvest tag, are properly stored, and are kept as fresh as possible. And if you see any cracked or broken shells, avoid them at all costs.
The people serving your oysters should feel comfortable answering any questions you may have about where their products come from—any other response should raise suspicions. And if you want to be extra careful, you can ask to see the oyster tag yourself.
