Are oysters vegan? The definition, the science gap, our line

No. By The Vegan Society’s definition, an oyster is an animal, so it isn’t vegan. Whether eating one hurts anyone is a separate and much harder question: a first scan of the scientific literature by Wageningen researchers in 2022 found no paper that directly showed whether bivalves are sentient or not.

That search is the detail I’d hand anyone who has argued about oysters at a dinner table, from either side. It was commissioned jointly by the Dutch shellfish industry’s quality foundation and a Dutch foundation for the protection of fish, an industry body and a fish-welfare group, which strikes me as a fair pair of sponsors for this argument. The researchers ran search strings like “(bivalv* OR oyster* OR mussel*) AND (sentience OR sentient OR nociception)” through Scopus and, in what they called a first scan, came back with a handful of studies on how bivalves respond to predators, whether they learn, and what serotonin does in their bodies. Those papers, they wrote, indicate that bivalves might be sentient, but the evidence that bivalves can perceive feelings or learn is very limited, and there are still large knowledge gaps. “No brain, no pain” claims more than that literature does. So does “they’re animals, so of course they suffer.” The same kind of unanswered question sits under whether going vegan helps animals at all, where the honest answer also turned out to be about odds.

The case for eating oysters, at full strength

When Slate’s Christopher Cox emailed Peter Singer, the philosopher behind Animal Liberation, about oysters in 2010, Singer was honest about wobbling: he had “gone back and forth on this over the years”. He allowed perhaps “a scintilla more doubt” about oysters feeling pain than about plants, and called it extremely improbable. You could give them the benefit of the doubt, he wrote, but “you could also say that unless some new evidence of a capacity for pain emerges, the doubt is so slight that there is no good reason for avoiding eating sustainably produced oysters”.

The farming side of the case is strong too, and its numbers come from NOAA Fisheries. Past the hatchery, where larvae are fed algae, NOAA says oysters need no feed, because they filter phytoplankton straight from the water, and that an adult Pacific oyster can filter up to 50 gallons of seawater a day. Its fact sheet on shellfish farming adds that no feed or fertilizer is typically required, and that shellfish remove nitrogen by building it into their shells and tissues. NOAA describes oyster farming as having a benign ecological footprint.

Put those together and the ostrovegan argument is serious. If veganism exists to spare animals suffering, and the animal in question very probably cannot suffer, and the farm that grows it helps clean the water instead of clearing a field for feed, then refusing the oyster protects a word rather than anyone. That is the strongest version, and I think it deserves a better answer than a shudder.

What the word actually says

The Vegan Society’s definition does not start from sentience. In dietary terms, it says, veganism means dispensing with all products derived wholly or partly from animals, and its own list of what that rules out names shellfish. Bivalves are aquatic animals in the phylum Mollusca, as the Wageningen report puts it, so an oyster fails the definition before anyone asks what it feels. People who eat bivalves and no other animal product sometimes call themselves ostrovegans. That word isn’t the one on the label.

UK law leaves bivalves out for now. Its Animal Welfare (Sentience) Act 2022 counts vertebrates as animals and, among invertebrates, only cephalopod mollusks and decapod crustaceans, and it lets the Secretary of State bring other invertebrates in by regulations that both Houses of Parliament approve. It is a definition built to be extended.

Our line

Our line at Vegan Pots is that oysters aren’t vegan, and that we won’t call a dish vegan if it has oysters or oyster sauce in it. The word describes a diet without animals, and a vegan ordering from a menu relies on it meaning exactly that. At a buffet, ask about oyster sauce in anything stir-fried; our guide to eating vegan at a work event has the rest of the questions worth asking.

We also think an ostrovegan eating farmed oysters is making a far more defensible choice than the usual eye-rolling allows, and we won’t claim evidence of suffering that a first scan of the literature didn’t turn up. Where nobody can tell whether an animal feels anything, and skipping it costs a vegan almost nothing, we would rather skip it. That is our call on uncertainty, and we flag it as ours.

The part I’m least sure about is what happens if the evidence does move. The Wageningen team recommended a full literature review and then experiments. If those come back with nothing, the label stays where it is, because the definition never depended on what an oyster feels. The uncertainty behind our choice to skip them gets thinner, though, and I don’t know yet whether that choice should hold on definition alone. Honey raises the same question about where use ends and harm begins, and our honey piece comes down on the same side for a different reason.