Norfolk livestock farmers have defended their green credentials and highlighted the importance of a balanced diet in response to the annual Veganuary campaign.

Veganuary aims to inspire people to try a meat-free vegan diet and champions "compassionate food choices with the aim of ending animal farming, protecting the planet and improving human health".

This week, it reported that more than 500,000 people have already signed-up for this year's 31-day vegan challenge – the largest number since the pledge began in 2014.

In response, the Agriculture and Horticulture Development Board (AHDB) has launched a £1.5m “Eat Balanced” advertising campaign on TV, social media and supermarket packaging, to highlight the "nutritional benefits of enjoying red meat and dairy, whilst showcasing Britain’s world class standards in food production and sustainability".

It says beef, pork and lamb are important sources of protein and nutrients that contribute to good health, including vitamin B12, an essential nutrient not naturally present in a vegan diet.

AHDB’s chief marketing and communications officer Christine Watts said: "Our farmers operate to some of the highest standards in the world and this campaign aims to balance the negative commentary around farming as well as the importance of eating red meat and dairy as part of a balanced and healthy diet."

That message was echoed by Norfolk cattle farmer James Runciman, who is a member of the National Farmers’ Union’s East Anglia livestock board.

Mr Runciman, who farms near Fakenham, said: "A balanced diet and a balanced environment is where we should be.

"I am not a human nutritionist, but I am a bovine nutritionist so I am well aware that you need a completely balanced diet to get the best performance. If one key part is missing you are going to suffer. You cannot artificially replace all the minerals, vitamins and proteins all the time."

The livestock industry is under pressure to reduce its greenhouse gas emissions, but Mr Runciman pointed to the sustainability of meat as a protein source in a country where 65pc of available farmland is best suited for growing grass for grazing animals, rather than crops for human consumption.

"Livestock have this recycling ability to use foodstuffs that humans cannot eat and convert it into proteins," he said.

"With almond milk or soya you are chopping down rainforests thousands of miles away, artificially irrigating and adding more chemicals to the human food chain to create a product that is inferior to cow's milk. I would rather people eat balanced and eat local, to support local businesses.

"The annoying thing is that people keep saying beef is the evil, but they are quoting massive US feedlots grown on soya, rather than British beef grown on grass in a way that completes the carbon cycle and has worked for centuries.

"Less is more. Food is very cheap and we do have a habit of over-indulging, particularly at this time of year. But we don't need to eat quite as much. We can eat less quantity but better quality. We can make huge steps with a regenerative approach rather than this 'smash and grab' of just getting rid of livestock.

"That is the way we should be going, then everyone can work together to embrace the change and we can all be healthier."

As well as its 500,000 participants, Veganuary says another major landmark in this year’s campaign is the involvement of Britain’s major supermarkets, with many creating dedicated web pages to promote meat-free products and advocate the reasons to try a vegan diet, including health and environmental benefits.

Mr Runciman said he believes this is partly due to higher profit mark-ups for plant-based proteins.

But Toni Vernelli, Veganuary’s head of communications, said: “The way British supermarkets have embraced Veganuary this year is truly game-changing.

"They are not simply using it as a marketing opportunity but are promoting the many benefits of plant-based eating and encouraging people to give it a try. As bastions of our food supply, they know that the only sustainable way forward is plant-focused.”