Who’d have thought a sardine could make me cry? But opening a tin of the tiny fish, I felt my eyes fill with tears.

After three years of strict veganism, I did not want to eat the dead creatures inside. Yet I was under strict doctor’s orders to do so.

This unwelcome dietary U-turn last August followed two years of medical investigations in an attempt to diagnose an often agonising set of symptoms that had left me feeling inexplicably unwell for nearly three years.

I’d endured blood tests, unpleasant examinations, a biopsy and seemingly endless visits to the GP, hospitals and specialists. At one point I’d even (alarmingly) been referred to an oncologist.

And yet the cause of my mysterious medical issues turned out to be both more prosaic and yet also more life-changing than anything I had imagined: it was my diet.

Flic Everett, who was vegan, has been advised by doctors to eat fish for the sake of better health

This month it’s estimated that 350,000 people are taking part in Veganuary, giving up any foods containing meat or animal products to save the planet, animals and their health.

For many, the decision is made on a wave of New Year resolutions, after weeks of festive gluttony. But while I applaud those who want to make this change, I know from experience that it’s not a dietary decision that should be made lightly — and certainly not without medical advice.

My problems began back in October 2016. I had been editing Vegan Living Magazine since June that year. A long-term vegetarian, I ate no fish or meat but I did eat cheese and drink milk.

When I got the job, it was the trigger I needed to go vegan. I love animals. I couldn’t look the nearby cows in the eye while supporting an industry that enforces pregnancy then takes away their calves; even free-range eggs meant the death of chicks. I was happy knowing I wasn’t responsible, even indirectly, for their suffering.

An issue of Vegan Living is pictured above from June 2017. At that point Flic had been editing it over a year

But I knew it would be tricky — I live in the Scottish countryside, where fellow vegans are rare and local menus haven’t quite caught up with the metropolitan elite.

However, I love cooking, and my new job gave me the impetus to try dishes I’d never considered: carrot and cashew paté, beetroot and pistachio roast and chocolate mousse made with ‘aquafaba’ — the water from a can of chickpeas. It was an exciting new way of eating, and I took to Instagram to show off my creations.

My conversion to veganism chimed with national trends. According to one survey, 2016 was the year it really took off in the UK, with numbers leaping from around 540,000 then to an estimated 3.5 million today.

And with eco-campaigners singing the praises of a vegan diet, and supermarkets leaping on the trend with plant-based ranges, it’s become an increasingly easy change to make.

Flic would eat things such as chick peas (above) and soya milk in order to adhere to the vegan diet

I enjoyed looking for new ideas, and would stock up on chickpeas and lentils, tofu, tempeh (made from pressed soya beans), kale, oats and granola, hummus, and lots of nuts and seeds for protein, along with soya and cashew milk.

I also had plenty of help via my new job. I was bombarded with delicious-looking cookery books, and sent information about the latest vegan restaurants and products.

In a world of climate change and animal cruelty, being vegan seemed a sensible choice, and though I tried not to preach to my omnivore partner and friends, I wanted everyone to know what was possible.

It was also becoming clear that veganism carried significant health benefits — numerous studies have found that a vegan diet lowers the risk of heart failure, stroke and certain cancers.

I knew a strict vegan diet meant a lack of vitamin B12 — which doctors warn can cause memory issues, breathlessness and, in extreme cases, even paralysis — and omegas 3 and 6, but I took vitamins religiously, including algae supplements instead of cod liver oil.

An assortment of fresh fruit and vegetables is pictured above. Vegetables and pulses are staples in a vegan diet

I prided myself on my balanced eating regime, full of chickpea curries, cashew cheese and tofu stir-fries, with treats of dark chocolate, soy-based ice cream and cakes made with flax seeds instead of eggs.

With full-time access to nutritionists, dietitians and vegan experts, when I started to feel unwell it never occurred to me that my problems could be related to my diet.

The trouble began with a stinging pain whenever I went to the loo. When it didn’t clear up, I went to see my GP, thinking it could be a form of cystitis. After undergoing a slightly embarrassing examination, I was prescribed some barrier cream. My GP wasn’t sure what the problem was — it wasn’t cystitis — but she didn’t think it was too serious.

As the weeks went by, though, it got worse until I was in daily pain. I made another GP appointment. She took a look, told me the problem was probably due to perimenopause, and prescribed mild HRT.

Relieved to have a diagnosis, I spent another month waiting for things to clear up. But nothing improved, and I’d also developed bleeding gums every time I brushed my teeth.

They had always been fairly robust, and as I go mad with an electric toothbrush and interdental brushes twice a day, I had no idea why I was suddenly emerging from my teeth-cleaning routine looking like Dracula after a tasty feeding session.

Meanwhile, I had developed regular morning headaches and an odd, stippled patch of skin near my mouth. At 48, I felt as though I was falling apart, so back I went to the GP. I was beginning to worry that something was seriously wrong.

I was examined again — by now, I had lost all embarrassment: I just wanted answers.

She suggested it was due to a chronic candida infection, and prescribed Canesten. It was no help at all. She also told me to wear only cotton underwear, avoid bubble bath and scented soap, and wash my sheets in non-bio powder.

I did as she said, swapping my lovely bath oils for dull prescription emollients and my fancy undies for white cotton granny pants. Nothing changed.

Another couple of months passed, and I was starting to feel like a problem patient. My sex life was non-existent, due to the almost constant pain, and I began to think it might be permanent.

I’d lie awake in bed, checking off the possibilities: I didn’t smoke or eat junk food; I didn’t know of anything hereditary that might be causing this.

In desperation, I turned to Google. Several forums popped up, full of worried women suffering similar symptoms. ‘Could be cancer — have you asked your GP for a referral?’ was one comment that leapt out at me. Horrified, I researched further, and found several descriptions of cancers that seemed loosely to match my symptoms.

A few weeks later, I was at a large city hospital, having a severely painful biopsy. ‘Do you think it’s cancer?’ I asked the consultant, as she finished.

‘Unlikely, but I can’t say,’ she said, condemning me to several more weeks of dread before the results came through clear.

It was a huge relief — but, of course, I was no closer to finding an answer.

I did wonder whether it could be a food allergy. I have hay fever every summer, and antihistamines seemed to provide temporary relief from the itching. But all the information I found suggested food allergies caused eczema, wheezing, nausea — I had none of these.

It was only when I was sent back, yet again, to the hospital, for another cancer specialist to ‘definitely rule it out’ that things changed.

The consultant was sympathetic, and he listened. I rattled through my symptoms, and ended desperately: ‘I just can’t go on not knowing what’s wrong with me!’

Then he asked: ‘Tell me, do you wear jewellery?’

He carefully bent back my right ear and looked behind it. ‘Hmm. Red,’ he said.

We established that most cheap jewellery gave me a rash and made my skin itch.

‘OK,’ he said. ‘I think we have the answer — you have a nickel allergy.’

How common is veganism in Britain? Last year Britain was recently declared the vegan capital of the world, taking Germany's title after UK supermarkets launched the most plant-based products in 2018. Analysis shows while more consumers are completely ditching meat, dairy and eggs from their diet, one in three of the total population have been cutting back on food consumption. The trend for a diet free of any animal products, particularly led by young people on ethical grounds, saw high street baker Greggs launch a vegan version of its popular sausage roll last year and a vegan steak bake yesterday. Greggs launched a vegan steak bake this month McDonald's is now offering a vegetarian Happy Meal, while KFC and Subway also launched vegan alternatives this week. Edward Bergen, of retail analysts Mintel, said with about one in six new food products containing no animal ingredients – double the eight per cent in 2015 – it was now easier than ever to try a plant-based diet. He added: 'For a number of years Germany led the world for launches of vegan products. However, 2018 saw the UK take the helm.' The UK has seen a huge promotion of vegan choices in restaurants and the expansion of supermarket own-label options, with dedicated vegan ranges in mainstream stores. Additional space is also being freed up to promote vegan food and drink. Recent analysis from market research company Mintel shows more consumers are completely ditching meat and opting for a vegan diet (file photo) Advertisement

This made no sense. There was no nickel in my knickers, I pointed out.

He explained that a great deal of food contains the chemical element nickel. The body can’t absorb it — and the excreted nickel from my food was causing a horribly painful rash.

My gums were bleeding for the same reason: my soft tissue was being attacked by nickel.

I was so relieved to have an answer, I almost hugged him. We backed up the diagnosis with a patch test, which revealed a severe nickel allergy.

My extreme reaction is so unusual the NHS was lacking in dietary advice, so back home I Googled ‘nickel in food’ and the results shocked me to my core.

The most nickel is to be found in soy — a mainstay of a vegan diet — pulses (tick), nuts and seeds (I ate them daily, thinking I was being healthy). Other culprits were kale, dark chocolate, tofu (made from soy), tomato seeds (I ate tons of tomatoes) and oats. Foods containing no nickel whatsoever are fish, meat, eggs and dairy products.

Nickel had, effectively, become my entire diet. I had dramatically worsened a mild allergy by turning vegan. My partner, Andy, immediately pointed out: ‘You can’t be vegan any more.’

I refused to believe it. I was committed to my cruelty-free regime — and besides, if I wasn’t vegan myself, how could I edit a vegan magazine?

I tried for several weeks to cut out all the nickel-based food I was consuming, including coconut milk, tinned goods — because nickel leaches from the can — and plant spread (soy again), a vegan version of butter. I was left with a few vegetables, vegan Quorn pieces, and seitan, a meat substitute made from wheat gluten.

My symptoms improved almost overnight — but from a dietary perspective, it was utterly miserable. And while my rash disappeared my overall health did not.

I was constantly tired, pale, and depressed — I no longer enjoyed eating. Even after I reluctantly added cheese and eggs, things didn’t improve.

So I called my GP again.

‘You have to at least eat fish,’ she told me. ‘You’re simply not eating enough protein. For goodness sake, this is about your health, and what you are eating is not a sensible diet.’

With the universe’s mischievous logic, that week I found out my magazine was closing. I decided I may as well listen to my GP’s advice, despite my reluctance.

My animal-loving ideology was about to be sacrificed for my health. And though I knew I was making the right decision for my body, emotionally, I wasn’t happy.

Yet within a couple of days of re-introducing fish (I was so guilt-stricken, I felt I should apologise to it), I felt significantly better.

My energy came back, my skin improved, and the headaches disappeared. A few months on, my rash and pain have entirely gone and my gums are fine.

I have been in two minds about revealing what happened to me.

In my heart, I would love to be vegan again. I feel horribly guilty about the fish, though I eat only those that have been ethically caught such as line-caught tuna and sardines, and I won’t ever be persuaded to eat meat.

While being vegan can be healthy, my consultant suggested that anyone with a nickel allergy — said to be as many as one in ten of us — should beware.

It’s increasingly clear I’m not alone in encountering issues. One clean-eating journalist recently wrote about developing kidney stones from the high levels of oxalates (found in plants) in her food. Several celebrities, with access to the best nutritionists, have stopped being vegan.

Actress Anne Hathaway recently admitted that she started eating fish again because filming was demanding, and as a vegan she ‘didn’t feel good or healthy’; while fellow actresses Kristen Bell and Natalie Portman both went back to dairy when pregnant.

Anne Hathaway (left) said she started eating fish again. Kristen Bell (centre) and Natalie Portman (right) both went back to eating dairy when they were pregant

And though Beyoncé follows a vegan diet when ‘getting in shape’, it’s not a permanent regime. Even committed vegan, actress Zooey Deschanel, gave in and now says: ‘I have a lot of food sensitivities — I can’t eat wheat or soy — and it was very difficult to . . . get enough calories. It was even impossible to eat at a vegan restaurant.’

Many other vegans have ended up with vitamin B, D, calcium and iodine deficiencies — all essential for good health. A significant lack of vitamin B can lead to heart and nerve problems.

I don’t suggest that veganism is a bad choice — simply that unless you know what you’re doing, and are very careful to monitor your body’s reactions, you could, like me, end up with a problem.

This year I am still cheering on those doing Veganuary. But sadly, in future, I won’t be joining them —because for me, the diet I believed was best turned out to be the very worst.