If you’re looking for seafood that’s good for both you and the environment, you may be surprised to know that oysters can be a good choice.

Oysters, which are bivalve mollusks in the family Ostreidae, have been eaten raw (meaning alive) or cooked (steamed, baked, broiled, stewed, fried) for centuries as both a poor person’s food and a luxury item, as well as for their supposed—though never proven—aphrodisiac powers.

The nutrition lowdown: Oysters are low in calories and total fat, yet rich in omega-3 fats, as well as iron, zinc, copper, selenium, and other minerals. A dozen medium farmed eastern oysters (about 6 ounces, raw) have only 100 calories and 3 grams of total fat—but about 650 milligrams of heart-healthy omega-3s, a good daily goal. And they’re low in cholesterol, especially compared to shellfish like lobster and shrimp. Wild eastern oysters and Pacific oysters have slightly more calories, fat, and cholesterol—but also more omega-3s (1,000 to 1,200 milligrams in 6 ounces, raw). Battered and fried oysters are another story: they have about 450 calories and 22 grams of fat in 6 ounces. Canned oysters, often smoked, have added sodium.
The environmental angle: Wild oyster stocks have declined over the years due to overharvesting, but most oysters today come from well-managed, nonpolluting, sustainable ocean farms. Moreover, because oysters are filter feeders, they actually help keep waterways clean. According to the nonprofit Monterey Bay Aquarium, farmed oysters are a “best bet choice” for ocean-friendly seafood, while wild-caught are a "good alternative."
The safety factor: The tradition of avoiding raw oysters during months that do not have an “r” in their name (May through August) was born in the days before refrigeration, when oysters were more likely to spoil. The truth is, while some oysters may be riskier in summer months, they can carry harmful pathogens, including Norovirus, at any time of year due to contaminated waters, and Vibrio vulnificus, bacteria that occur naturally in unpolluted marine waters but multiply rapidly in warm weather. Gulf coast oysters are particularly susceptible to Vibrio, which can cause mild illness in healthy people, but severe illness in people who are immune-compromised or otherwise at high risk.
Some retailers and restaurants sell oysters that have been specially treated to kill Vibrio, but these processes may not destroy all bacteria or viruses. It’s thus safest to eat all oysters thoroughly cooked, especially if you have compromised immunity or a chronic medical condition (such as liver or kidney disease), are elderly, or are simply in frail health. Pregnant women and young children should not eat raw or undercooked oysters either. When cooking oysters, toss any that remain closed; this may indicate that the oysters were dead before cooking and are unsafe to eat.