IT’S always the small things that trip you up. Nineteen days into a vegan diet, and feeling reasonably pleased with the way things had been going, I reach into the fridge and, in a casual gesture born of years of practice, nibble some Edam cheese. Dairy produce, in other words. Damn. Vegans aren't supposed to eat dairy produce – no milk, no cheese, no eggs.

“Don’t worry,” Craig Tannock, a vegan of some 30 years' standing, and owner of several Glasgow vegan restaurants, says when I mention this to him later. “Vegan cheeses have been transformed in the last five years. Vegans don’t have to give up cheese any more. There are dairy-free cheeses that are completely acceptable. Until recently, they were unpleasant, and only vegans who missed cheese would contemplate eating them. But now, they are so much better.”

I've been experimenting with veganism for a few weeks now, largely prompted by the fact that there's a two-day vegan event, VegFest, at the SECC (December 5-6), followed by Veganuary, which invites people to go vegan for January, 2016.

People become vegans for all sorts of reasons: for better health, for the environment, to prevent animal exploitation. The more I've read about the exploitation of animals, the more sickened I have felt.

Paul McCartney once appeared in an ad for PETA – People for the Ethical Treatment of Animals – in which he recalled a fishing trip years earlier. Reeled in a fish, he had watched it fight for breath, and realised something important – that "his [the fish’s] life was as important to him as mine is to me".

Though it took me a long while to recognise the truth of that, for the past three years, I've been experimenting with veggie dishes: home-made, store-bought. I bought Quorn meat-free meals (it does a nice roast, and a tasty tikka masala with rice) and the late Linda McCartney's own range.

But something was missing. I felt like a hypocrite: how can you be appalled by images of animal exploitation and still wear leather?

I'd been interested in PETA's work for a while: it's an outspoken, crusading sort of organisation, not afraid to stir controversy. Its website (like that of the Vegan Society) has much information about vegan lifestyles. My eye was caught the credo on the home page: "Animals are not ours to eat, wear, experiment on, use for entertainment or abuse in any other way." PETA's hard-hitting videos about animal exploitation are pretty hard to watch, which I suppose is the point.

The organisation has attracted much criticism over the years. Last year, Peta ran ads asserting that studies had shown a link between cow's milk and autism; one critic retorted that this was a "kind of zombie pseudoscience revival that appears to be a common tactic in certain circles". One animal-research advocacy group argues that if PETA had got its way 30 years ago, "we would not have vaccines for HPV, hepatitis B or meningitis, nor would we have treatments for leprosy, modern asthma treatments and life support for premature babies".

PETA has its critics, then, though actress Pamela Anderson, who has worked with PETA for two decades, describes the campaign's methods as "brilliant". If nothing else, its approach can jolt people out of their apathy. It jolted me.

Other factors are equally hard to ignore. Five years ago a UN report called for a worldwide shift to a vegan diet in response to the problems of hunger, fuel poverty and climate change. Jeremy Corbyn's shadow environment secretary, Kerry McCarthy, is a vegan who is becoming “more militant” over the environmental impact of livestock farming and believes that meat "should be treated in exactly the same way as tobacco with public campaigns to stop people eating it”.

So what is veganism? According to the comprehensive handbook, Becoming Vegan, it involves a diet that avoids meat, poultry, fish, dairy products, eggs and gelatin while the vegan lifestyle excludes clothes made from fur, leather, wool or silk. Vegans don't use personal-care or cleaning products from animal-derived ingredients.

At home I try vegan recipes, such as three-bean chilli with spring pesto. Out goes full-fat milk: in comes soya milk and almond milk. Soy lattes become my new morning addiction. I start buying vegan multivitamins from a health-food shop.

Clothes, however, are a more complicated issue. From M&S, I buy non-leather shoes, an acrylic scarf and a belt made from cotton and elastodiene, which is a start, but hardly a full wardrobe. More work is needed.

"When I went vegetarian then vegan, I went for the full lifestyle," Tannock tells me. "I haven’t worn wool or leather for decades. In terms of footwear, you just need to look at the labels and see what the various symbols mean and know what is and isn’t leather. Now, the rare times I upgrade my footwear, I’ll normally go to a specialist veggie or vegan outlet. That’s something I’d really like to do, eventually, to have somewhere where you can try on [vegan-friendly] shoes in Glasgow, because normally you have to get them sent to you by post.

“Over time, you can pick up a lot of information. The great thing now is that there are so many other people around in terms of the internet. There’s much more a community, more resources, than there ever was. When I first went vegan, it was five years before I met another vegan."

Tannock, it's worth pointing out, is heavily involved in The Only Way Is Ethics, a week-long, multi-disciplinary ethics festival in Glasgow that culminates in VegFest.

"I really do feel that veganism is becoming more mainstream," says Jane Land, co-founder of Veganuary. "It's mentioned more in the news, and in Google Trends it has overtaken 'vegetarian' in the last few years as a search term. If you mention 'vegan' in restaurants, not only do they understand, but they have options on the menu. We'd like to think that Veganuary is maybe part of that, challenging people to try vegan for a month."

Does the world's never-ending mania for meat ever get her down? "When I go out and see my friends and family eating meat around me," she says, "I just have to focus on what we are doing. Each Veganuary we're creating more and more vegans." Some 76 per cent of people surveyed after last year's event reported better health and energy levels."

To an aspiring vegan, those are cheering statistics. But why avoid products such as wool, which don't involve killing animals? "Some of the means of obtaining wool can be quite horrible," says Land. "I've seen some nasty footage of how sheep are sheared. Some sheep can die because of the way they are handled, and from the shock of the process." Some vegans buy second-hand leather and wool items from charity shops, in the belief that they're not interfering with the supply-and-demand chain. If money is tight, this option might be acceptable, she adds.

Yvonne Taylor, senior manager of corporate projects at PETA UK, advises vegans keen to make a difference to "contact retailers, asking stores, saying you're looking for items that are wool-free, leather-free. "Retailers do listen," adds Taylor, who's been vegan for more than 20 years. She believes veganism is becoming mainstream. In fact, "it's actually hip and fashionable to be vegan. With all the reports about the environment and population growth, it all just comes together. More and more people are looking at it and thinking, 'I don't want to support this cruelty, this devastation of the environment, the treatment of people in Third World countries'. It's so easy to be vegan once you're into it and get used to it."

There's no doubt that veganism's image has improved in recent years. There are now said to be around 300,000 vegans in the UK. Numerous celebrities and athletes swear by the vegan lifestyle. Quorn has introduced a vegan range and from late next year, Guinness will no longer contain trace amounts of fish bladder, a key part of its filtration process. The food in vegan restaurants is very good, like the roasted beetroot and kale salad with chickpeas and sun-dried tomatoes in a Caesar dressing that Tannock and I share at Mono.

I've read that some vegans have been described as "bores" by people antagonised by a (possibly imaginary) puritanical attitude. What's wrong with eating burgers?, they'll argue. You can eat fried chicken and still try to change the world. It's an interesting question, one better dealt with, I suspect, by vegans of long standing who really know what they're talking about. My simplistic view, for what it's worth: no-one forces you to go vegan. If it works for you, fine. If not, fine. You think veganism is for cranks? Fine.

One valid question, though, is whether we can get everything we need from a plant-based diet. "In terms of the main nutrients," says Dr Emilie Combet Aspray, a lecturer in human nutrition at Glasgow University, "assuming that you have a great knowledge of foods, the vegan diet should be able to provide you with everything you need, with the potential exception of vitamin B12. It depends on how strict a vegan you are – I know some vegans who take yeast product for the B12. Others regard yeast as an unacceptable part of the vegan diet. B12 is potentially a problem but it can be found in fortified breakfast cereals, for example. A B12 supplement might be a good idea.

"If you select your foods carefully you should be able to secure all the nutrients from the range available to vegans, but that is very difficult, because the knowledge of food of anyone not trained in nutrition is usually not to the extent that they can anticipate every requirement." While Omega-3 fatty acids are present in seafood and oily fish, she adds, they're also present in rapeseed oil, certain nuts and fortified eggs. Calcium is in dairy products but in some plant sources, too; iodine "might be another issue, though the vegan diet can benefit in this respect from seaweed." Dr Combet Aspray says knowledge is the key, and that seems right.

I plan to continue with my vegan experiment. Thus far, it's been easier than I expected, though having been vegetarian for three years certainly helped in that there was no meat-heavy diet to overcome. There are hundreds of vegan recipes available, in book form or online; sourcing vegan-friendly clothes, however, will require more of an effort. The thing is: it's worth it. Vegans avoid exploiting animals for any purpose and that's an impulse I feel more and more in tune with, notwithstanding the fact that I unthinkingly wore leather shoes for years. It's clear that I've got a lot to learn, a lot to think about. But the first steps have gone well. The next ones, in which nascent vegan beliefs will, I hope, take root, hold no fear.

* www.vegfestscotland.co.uk; www.veganuary.com; www.peta.org.uk; www.vegansociety.com; www.monocafebar.com. Becoming Vegan: Express Edition, by Brenda Davis and Vesanto Melina, Book Publishing Company, £17.99