Historically found languishing soggily under a coating of lumpy custard, rhubarb has taken on a new lease of life, thanks to its discovery by health-conscious eaters.

Sales have doubled in the past year alone after the “forgotten vegetable” was championed by celebrity chefs and dieticians. Those red stems are low in carbohydrate but high in vitamin C, dietary fibre and potassium.

One of the chefs responsible for the rhubarb renaissance, Antony Worrall Thompson, has featured it heavily in his two books on the GI diet.

“I think the GI diet plays a part in the recent rise in demand for rhubarb,” he said. “Rhubarb is very healthy and it is excellent for the GI diet because it is low in carbohydrate.

“You can put it in a crumble and, as long as you don’t have too much sugar, it is very good for you. My favourite dish is a hot or cold rhubarb crumble or tart.”

Supermarkets experienced a 100 per cent increase in sales this January in comparison with 12 months ago — a faster increase than any other vege- table.

Janet Oldroyd-Hulme, of Oldroyd’s Farm in the so-called “rhubarb triangle” between Bradford, Leeds and Wakefield, supplies Asda and Sainsbury’s.

Over the past five years she has increased production from 500 tonnes a year to 1,000 tonnes, enough to make a rhubarb crumble the size of an Olympic swimming pool.

Mrs Oldroyd-Hulme, 53, said: “For people on GI diets, like other diets, rhubarb is a godsend and they have been clamouring for it.

“Dieters refer to it as a superfood because it helps to push toxins out of your system and speeds up your metabolic rate. Rhubarb is also high in calcium yet actually lowers your cholesterol, unlike dairy products.”

Until recently, rhubarb was confined to a forgotten corner of the allotment where its enormous, and poisonous, leaves hid the rosy red stems from view. But it was not always like that, according to Mrs Oldroyd-Hulme.

She said: “It used to be more popular than strawberries in this country, and the rate we are going it may well be like that again one day.

“In the Second World War, when there was rationing, people used to get a stick of rhubarb and a bag of sugar to satisfy their craving for something sweet. That gave rise to the modern day sherbert dip. But after the war sweets became more widely available and rhubarb got left behind.”

Claire Taylor, a spokeswoman for the supermarket chain Morrisons, said that one of the reasons rhubarb was more in demand was the GI diet. She added: “Rhubarb has always had a loyal following, but it seems that its popularity is on the up.”

The earliest records of rhubarb growing are from 2,700BC in China, where it was cultivated for medicinal purposes.

In Britain the plants spend two years in the open, absorbing sunshine and storing energy, before they are put in darkened sheds and warmed. In this way they grow longer and sweeter stalks, instead of producing leaves.

At the height of its popularity there were 200 growers in the rhubarb triangle and the area produced 90 per cent of the world’s winter rhubarb.

The GI — or glycaemic index — diet emerged about 1970 as a way for diabetics to control their insulin levels, but has since replaced the Atkins diet as the trendy way to lose weight. Among its enthusiasts are Kim Cattrall, one of the stars of Sex and the City, the model Jodie Kidd and the singer Kylie Minogue.

RISING TO A CHIC NEW ROLE: Rhubarb soup and Lamb and rhubarb ragout

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