My preschooler

- Mummy, are sausages dead baby snakes?

Me

- ...no?

My preschooler

- Of course not. I think they're dead eels.

The Vegan Diet

A vegan diet contains only plant foods. That means no meat, poultry or fish, no dairy, eggs or honey and no foods processed with animal products (like some wines and beers).

Some people eat vegan because of their religion, health or politics. Some think it's wrong to eat animals. Others would be happy to partake but are horrified when they learn about the animal welfare standards in our modern food system.

Many people also become vegan for environmental reasons. Generally, a plant-based diet uses less water and land and causes less deforestation. It also generates less carbon dioxide and equivalent emissions (CO2e). Some vegan ingredients, like soy and palm oil, raise their own environmental issues, but the overall impact is lower.

Eat Vegans?

We Australians eat a lot of meat and dairy. On average, a third of our kilojoules come from animals. It's a little outdated, but 'Hungry Planet: What the World Eats' (2005) surveyed food from 30 families in 24 countries. Australia ranked fifth highest on meat consumption, eating an average of 94 kilograms per person per year. One 'Hungry Planet' Australian family ate almost 1.5 tonnes of meat over the year, primarily beef. Compare this to the average in Bhutan, India and Japan, where they respectively eat 3, 5 and 44 kilograms of meat per person per year.

I've thought about eating vegan before. I pitched it to my partner several years ago. Our conversation ran like this.

Eat vegans? he said. Are you sure? Good for the planet. Bad for the vegans.
No, eat vegan. As in no meat, no fish, no dairy, no eggs.

Great idea, he said. I'm not doing it. I'll cook for myself.
What will you make?
Steak.

Ironically, going vegan would have tripled my household's environmental impact, so I abandoned the idea. But I managed to win the beef about beef for a one week vegan experiment. The results were pretty impressive.

Maurice? Speak to me, Maurice!

How much CO2e did I save?

Before starting these food experiments, I took a baseline for my usual diet, which generates around 20.2 kilograms CO2e each week. Switching to a vegan regime generated less than half that, only 8.8 kilograms CO2e (and I think I these numbers are artificially high, see notes for details). At this rate, eating vegan would save me 600 kilograms CO2e over a year.

I compared this vegan diet to the 'average' Australian diet (the Molloy family from 'Hungry Planet'). They'd save over 970 kilograms CO2e each year by eating this way. That's a huge chunk from a 22.5 tonne footprint and a bigger saving than anything I've looked at so far, except flying.

There are plenty of principled vegans out there who follow a strict code. I'm more of a pragmatist. A flexible vegan switch is easier to make and may be more likely to stick. Try cooking one vegan meal, or a day's worth, or become a weekday vegan or a vegan at home. Provided you don't binge on steak to make up for it, the savings are real.

What's it like to be vegan?

There's a huge range in vegan diets. You can eat healthy whole foods with lots of legumes, nuts, seeds and grains, processed mock meats and cheeses or mainstream junk food that happens to contain no meat or dairy.

We ate our regular meals (many of which are naturally vegan) with a few specialist additions, including our usual tofu, one terrible cheeze and one delicious one, a mock duck that made the best laksa I've ever tasted and a fantastic homemade fudge. I tried making coconut yoghurt but it went mouldy, so I ate my porridge plain. For Friday night takeaway we picked Indian, and it was almost as good as what we usually get. I drank my coffee black and ate a vegan chocolate when I met a friend at Koko Black.

I didn't eat out in a restaurant or at a family gathering. Both would have been a challenge. There are a lot more vegan options in restaurants these days and my local noodle bar has now listed a vegan banh mi because I kept requesting it (it's now a top seller). But I have no idea how we'd broach the question of a roast dinner at Grandma's if we ate like this all the time.

Top: My usual weekly food minus the meat and dairy; some vegan additions.

Bottom: Lentil nachos; curries; vegan breakfast with fake bacon.

I'm suspicious of processed food. There's a lot of it around for vegans, including fake chocolate, fake cheese and fake meats. You could practically go vegan without noticing, but it would be expensive and unhealthy. I prefer to increase my fats and protein with nuts, oils, seeds and legumes, but a little junk doesn't hurt. I also feel that swapping processed junk for junk doesn't lose out on nutrition. If you're already eating salami or devon sandwiches, substituting fake bacon or fake cheese probably won't hurt you.

There's a few tricks to making make tasty vegan food. Get inspiration from food cultures that are naturally low on meat and dairy (like Indian or Japanese). Buy a good vegan cookbook. Experiment. Make sure you add back the fat and flavour you lose when you take out the meat and dairy. Nuts, nut butter, oil, coconut milk, seeds and avocado all work well.

While specialist vegan foods can be expensive, so can meat and dairy. I found I spent less at the supermarket and on takeaway, even after I counted that delicious mock duck. If you can afford to eat now, you can probably afford to eat vegan.

Cautions - health, kids and conditions

Cutting meat and dairy should be healthy for most adults, but talk to your doctor first. They will almost certainly say you're eating too much meat - most Australians do - but might be more cautious about cutting back dairy. Personally, I suspect milk's sacred place in our food pyramid is down to good lobbying rather than good nutrition. Unfortunately, I can't show you a peer-reviewed long-term health study proving veganism is or isn't healthy, because we don't lock people in a lab and study them for 50 years. There are populations and countries that eat much less meat and dairy than us with good outcomes - such as Japan and vegan Hindus - but you should take your own advice.

If you want to eat vegan, the stricter you are, the more careful you need to be, particularly with calcium, iron, zinc and B12. You should consider eating whole foods of a wide variety, taking supplements and getting health checks.

I'm suspicious of strict veganism for kids, though many swear by it. During our weeklong vegan experiment, we ate dinners together as usual, but my preschooler had meat and dairy at other times.

Veganism may not work if you have particular health conditions. Remember, there are times in life when the best intentions don't pan out. For instance, during pregnancy, I couldn't digest legumes, and during childbirth, I lost 1.5 litres of blood. I've never eaten so much meat in my life. You can be all-or-nothing or you can do what you can when you can. It's your life and your planet.

Spreadsheet calculations, reference list and data discussion in the 'Notes' section, Week Thirteen.