‘I’ll have them with hot sauce’: should vegans eat oysters?

Alex Karol is fantasising about the next time she gets to slurp up some freshly shucked oysters. “I’ll have them with lemon juice, shallots, and a couple of drops of hot sauce. Sometimes, I have a couple with a splash of vodka,” says the London- and Toronto-based publicist. Cost curbs her craving for oysters to one meal a month, and so even just talking about them makes her hungry. “I really, really enjoy them – like, properly enjoy them. I wish that I had oysters every single day of my life.”

Oysters are not to everyone’s taste but Karol’s enthusiasm for the filter-feeding bivalves comes as a surprise – because she is vegan. She is otherwise strict: she does not even consume honey. But a few years back she found she was struggling to get certain nutrients in suitable quantities from plants alone, and someone tipped her off to the idea that you could eat oysters and still be vegan. It was called “bivalve veganism” – and Karol was sold.

“I was so excited to bring oysters back into my life,” she says, adding, however that “I do feel like lots of people think I’ve made up the rule myself, and it’s not a real thing.”

You can say, by definition, a vegan won’t eat oysters. But that doesn’t solve the ethical question of, ‘is there anything wrong with it’

Peter Singer

Bivalve veganism is built on the idea that molluscs such as mussels and oysters do not possess a brain and are unable to process pain, so eating them does not cause animal suffering. This has prompted a simmering philosophical debate: can vegans really consume oysters?

According to the Vegan Society , “In dietary terms [veganism] denotes the practice of dispensing with all products derived wholly or partly from animals.” Maisie Stedman, a spokesperson for the UK charity, says it “understands the word ‘animal’ to refer to the entire animal kingdom. That is all vertebrates and all multicellular invertebrates. Oysters and other bivalves are invertebrates and, taking this into account, it is not vegan to consume them.”

However, some say the argument is more nuanced. Philosopher Peter Singer says: “You can say, by definition, a vegan won’t eat oysters. But that doesn’t solve the ethical question of, ‘is there anything wrong with eating oysters?’”

Singer is emeritus professor of bioethics at Princeton University in New Jersey, US, and in 1975 published Animal Liberation , a book that argues for the more ethical treatment of animals. He decided to be almost exclusively vegan, so he would “not be complicit in inflicting unnecessary suffering on any sentient beings”. But occasionally he will enjoy an oyster, believing that oysters do not suffer pain.

To understand this, it makes sense to find out more about how pain works. Firstly, pain involves a “nociceptive response” where nerves react to a harmful stimulus, such as heat, by triggering a reflexive withdrawal of the exposed body part to protect it from further harm, says Lynne Sneddon, a professor at the University of Gothenburg in Sweden who studies aquatic animal behaviour.

For some organisms, nociception tips over into a second phase, sensory pain, which promotes behaviours such as nursing a wound. We know from human experience that sensory pain can lead to suffering.

But oysters and mussels lack what is considered a critical ingredient required to process sensory pain: a centralised nervous system, or brain. The logic follows that killing and consuming oysters causes them no suffering.

Adding to this theory, oysters and mussels are anchored to rocks and unable to flee their attackers compared with other bivalves such as scallops, which can swim away.

“It’s harder to see why [oysters and mussels] would have evolved the capacity for pain since there’s not much that they can do about being ripped off the rock,” Singer says.

Singer’s recent book, Animal Liberation Now, excludes scallops and clams from the list of bivalves he is happy to consume. But oysters remain on the menu. “I think that the ethical reasons for being vegan don’t apply to eating some bivalves. So I think that people who are vegan and would like to eat some bivalves … are justified in doing so.”

The subject of animal pain continues to compel researchers and, according to Sneddon, “there’s nowhere that it is more hotly debated than in aquatic animals”. Unable to get into animal minds, researchers rely on behavioural changes as the closest evidence that these organisms might experience pain. Sneddon’s own studies on behavioural changes in fish add to a mounting body of research suggesting that fish do feel sensory pain. Meanwhile molluscs such as octopuses have been observed cradling wounded tentacles, and other experiments show that such behaviours subside when animals are supplied with pain treatments.

Oysters and mussels show potential signs of nociception, such as closing their shells against a threat, Sneddon says. They may not have a centralised brain, but they do have a diffuse system of nerve cells, she notes: “Their [central nervous system] is just laid out differently.” And considering the close evolutionary ties between these bivalves and other molluscs, she thinks it is worth investigating further whether they can experience pain.

Related: Served up from the sea: 13 of the best sustainable eateries on the British coast

But there is currently almost no pain research underway on bivalves. “The jury’s out. We don’t have the science in place to inform anyone’s decision about that. But if you’re concerned that there might be a likelihood that these animals suffer in some way, then I would suggest you should avoid eating them,” Sneddon advises.

Sneddon and Singer agree, however, that there is more to this question than the welfare of individual animals, such as what seafood production does to wider ecosystems. “I’m a little bit biased: my concern is for the individual animal, that’s the priority,” says Sneddon. “But there are so many other questions about how the animals were caught, what was done to them and how that affects the wider environment – the ecosystem and other animals.”

For example, there is evidence that scallop dredging destroys whole ecosystems, which raises questions about how this affects the wellbeing of other living things. Similarly, while oyster and mussel farms filter the water and are generally considered the most sustainable aquatic foods you can consume, there are some concerns around the chemical pollution and wider biodiversity impacts linked to largescale bivalve farms.

While the research catches up with the philosophising, Karol, who identifies as a bivalve vegan, prefers to source her oysters from sustainable fisheries and farms. But, she says: “I’m always open to listening. I would be open for someone to sway me into complete veganism, for sure.”