There’s a good reason why humans have been eating shellfish like clams and mussels for at least 165,000 years: these mollusks are nutritional powerhouses high in protein, minerals and healthy fats. They’re also great for the health of the oceans too. Bivalves like oysters, clams, mussels and scallops are filter-feeders that actually make the water cleaner. And because they strain the water for food — eating both microscopic plants and animals — they don’t require supplements to their diet like fishmeal or fish oil, which can come from unsustainable sources.
One warning, though: Not all mollusks are safe to eat. Some that grow in polluted waterways are great at cleaning the water but they store some of those pollutants in their tissues. So they can be dangerous if they wind up on your dinner plate.
Luckily, in the United States, shellfish producers can only sell their products for human consumption if the animals are raised in water that meets high sanitation standards. And, compared to predatory species like tuna or sharks, bivalves are lower down on the food chain and usually contain a lot less mercury and other toxic metals, though cadmium is a concern in some areas.
Another concern when it comes to farming bivalves in some places is that non-native shellfish can become invasive and upset local ecosystems. It’s always good to try to buy native oysters, clams and their relatives if you can. But be careful: while most farm-raised bivalves are great choices, their wild-caught counterparts may have been hauled in using destructive equipment like dredges.