Given my job at Composite, and my fifteen years in the fitness world, I get a lot of questions from friends, family, colleagues, and clients about health and fitness. While the questions run the gamut – from exercise programming and injury rehab to sleep management and environmental toxins – the topic I’m asked about most is nutrition. Over the next couple of weeks, I’m hoping to hit a handful of posts that address some of the most common nutrition questions I receive.

First up, staying healthy as a vegan:

As I’ve blogged about before, I’m actually totally sympathetic to arguments about the ways in which our food system is unforgivably cruel to animals. In my own case, after weighing a lot of factors, I’ve decided that I feel comfortable eating a diet that includes ethically-raised animals, and ethically-farmed eggs and cheese. But I understand that includes tradeoffs that others aren’t willing to make. If you’re eating a vegan diet for moral reasons, I can understand and support that choice.

So, if you’re committed to a vegan diet, what can you do to maximize your health?

On the plus side, vegans tend to eat a lot of whole foods, which is great.

On the minus, they’re also frequently deficient in protein, omega-3 fatty acids, vitamins B12 and D, calcium, iron, zinc, and iodine.

Previously, I’ve blogged about some supplements that vegetarians and vegans should strongly consider, to counter those deficiencies.

But it’s B12, in particular, that’s a real issue for vegans. Simply put, while a variety of vegan foods have been held up as good sources of B12 – spirulina, dried nori, barley grass, other seaweeds, raw foods – an avalanche of research has shown that they’re not bioavailable enough for people to actually absorb the vitamin in those foods at meaningful levels. And B12 shots – beyond being a literal pain – use B12 in the form of cyanocobalamin, which steals methyl groups from the body and creates toxic cyanide as it’s processed in the liver.

There is, however, a good alternative: oysters.

I know, I know: oysters are technically animals, and therefore definitely not vegan. But bear with me here.

First, remember that vegans aren’t avoiding animal protein as an end in and of itself. Instead, they’re doing it to inflict the least possible harm to other sentient beings and to the environment.

Fortunately, from an environmental perspective, oysters are actually a net-positive. Farming them doesn’t require bottom-trawling or other destructive forms of fishing; it requires no carbon-emitting supply chain for feed, as the oysters simply eat by filter-feeding plankton in the water around them; and it actually improves the surrounding water quality, through that filter-feeding (enough so that places like NYC have planted oyster beds to help de-pollute their currently toxic waterways).

As for sentience, unlike almost every other animal, oysters don’t feel pain, because they don’t have a central nervous system. As Crook & Walters conclude in a 2011 paper:

[The bivalve] nervous system includes two pairs of nerve cords and three pairs of ganglia. There is no obvious cephalization and the nervous system appears quite simple….to our knowledge there are no published descriptions of behavioral or neurophysiological responses to tissue injury in bivalves.

In other words, oysters have a very simple nervous system, without a brain. Unlike other invertebrates, and even other shellfish, they don’t react to injury (unlike, say, shrimp and lobsters, which groom their antennae after injury), or show the neurotransmitter responses that other animals do when they experience pain.

So eating oysters (and likely mussels, too) doesn’t actually hurt them; they don’t feel it any more than a piece of asparagus does.

A lot of research has shown that the disgust reflex plays a big role in the vegan diet. And I’m sure the idea of eating oysters seems potentially disgusting to a lot of vegans, regardless of the moral, environmental, or health implications.

But as I’ve noted before, the long-term adherence to veganism (and vegetarianism) is terrible – after 18 months, about 85% return to eating meat, which is why the percentage of vegetarians and vegans has held steady at about 5% for the past thirty years.

According to research, some of them give up due to the social sustainability of the diet – and in my next nutrition post, I’m going to talk about behavioral diet sustainability in general.

But an even larger percentage of vegans (more than 50% of those who give up on the diet) due so either due to declining health, or irresistible food urges (which are often driven by a craving for micronutrients in which people are deficient). And oysters just happen to be a great source of every one of the nutrients in which the vegan diet is deficient (again: protein, omega-3 fatty acids, vitamins B12 and D, calcium, iron, zinc, and iodine), enough so that regularly eating oysters is likely to offset both declining health and animal-food cravings.

So, in short, if you’re a vegan, and you’re worried both about your own vitality and your ability to sustain a way of eating that does the most good for the world in the long-term, consider a happy hour trip to grab some oysters. Strange as it may sound, that’s totally in line with the goals of veganism – not hurting animals or the environment – and it will make you both healthier and more likely to stick with it.