“Some smart-arse scientist has just realised what we’ve known for god knows how many years,” Tony Chadwick told a customer on his black pudding stall in Bury market in Greater Manchester on Wednesday. “Black pudding is a superfood. Low in carbohydrates, high in protein, filled with essential nutrients. Lancastrian Viagra, I call it.”

Chadwick was vindicated this week when the product his family has been making to a secret recipe for the last 150 years has now been claimed as a superfood – alongside avocado oil, seaweed, kohlrabi and water made from the sap of a birch tree.

“I always knew black pudding was healthy,” said one customer, as she asked Chadwick to pick her a “good one” – a request which draw the response: “We don’t do good. Only very good or flippin’ excellent.”

Customers line up for ‘very good or flippin’ excellent’ black puddings from the Chadwick’s stall on Bury market. Photograph: Christopher Thomond/the Guardian

Fifty coach-loads descend on Bury’s lively market each day during the summer months to stock up on the £1.05 puddings, with other devotees travelling far and wide to sink their teeth into a Chadwick original. Trevor Hodgkinson, 64, had brought his wife Elaine up from Norfolk to taste the pudding he loved growing up in Hulme, Manchester. “You can get black pudding in Norwich, of course,” said Elaine, dousing her hot pud with vinegar and mustard, “but Trevor always says it’s not the same, and he’s right. The texture is very different – processed ones are often very dry. This breaks up nicely. It’s delicious.”

She washed it down with a smoothie she’d bought from another stall. “Cucumber, celery apple and lime – I was trying to be healthy,” she said, saying that she was pleased to hear that the black pudding wasn’t perhaps the health disaster she had feared.

“It’s funny, isn’t it? You think of superfoods and you think of berries. You wouldn’t think of black pudding.”

A customer eating black pudding from Chadwick’s, who have been making from a secret recipe for the last 150 years. Photograph: Christopher Thomond/the Guardian

The superfood claim was made by well-known nutritional oracle MuscleFood (an online shop specialising in lean meats for body builders). A spokesman this week claimed the pudding is becoming so popular with their health-conscious customers that they have declared it “a new buzzword in clean eating”, ranking it as a “superfood for 2016”.

Perhaps surprisingly, nutrition experts agree that black pudding can be part of a healthy diet, eaten in moderation. Rebecca McManamon, a consultant dietitian and a spokeswoman for the British Dietetic Association, said she didn’t believe in single superfoods but more super diets filled with nutritious ingredients. But black pudding could be beneficial for certain groups, she said. “Peri-menopausal women and teenagers, for example, or anyone at risk of anaemia.”

But back in Bury, Chadwick believes he is already one step ahead of the diet gurus. “I tell you what’s going to be the next superfood,” he said, pointing to a counter containing white blankets of animal stomach. “Zero calories there. Mark my words, the next big superfood will be tripe.”

• This article was amended on 7 January 2016. An earlier version misnamed MuscleFood.