Oysters are one of the more risky foods out there, largely because they’re “filter feeders” that remove plankton and other organic matter from the water around them, and can filter up to 50 gallons of water per day. Unfortunately, if that water contains a lot of harmful bacteria or other impurities, that can be bad news for whoever is eating it.
Thankfully, the odds of getting sick from an oyster are becoming increasingly small, thanks to the fact that the oysters we’re served at restaurants are cultivated, and the oystermen take great pains to make sure that the water the oysters grow in are as clean as possible.
But if you’re planning on downing some raw oysters and want to make sure there’s as little chance of getting sick as possible, there are a few things to keep in mind. One, know your oyster. Gulf oysters, for example, contain a relatively high bacterial load during the warmer months, so you may want to avoid them during the summer (the warmer the water, the more likely oysters are to spoil, so winter is actually the best time to eat them). Two (and this may be a little difficult to do when they’re served to you on the half-shell), make sure that the oyster was alive when it was shucked; if the shell of an oyster (or any bivalve) is open and doesn’t snap shut immediately when you tap it, throw it out. A good way to tell if an oyster you’re served was alive or dead when it was shucked is to give it a look and a sniff; If it doesn’t look fresh and doesn’t smell like the sea, don’t eat it. The odds of you being served a dead oyster at a reputable restaurant are just about nil; only the most careless of oyster-shuckers would ever serve one that’s dead. Cooking oysters also kills off any pathogens.
So if you want to minimize your chances of getting sick from an oyster, make sure it’s cultivated, make sure it was alive when it was shucked, and make sure it doesn’t look or smell bad. If you’re still concerned, make sure they’re cooked, and if you’re really concerned, well, nobody’s forcing you to eat them!