An ingredient of dark chocolate may help diabetics control dangerously high cholesterol levels, it is claimed.
Chocolate with high levels of cocoa solids is rich in polyphenols, which other studies suggest can reduce the risk of heart disease.
The Hull University study found cholesterol fell in a small number of diabetics given bars rich in this ingredient.
But Diabetes UK said the high fat and sugar content would outweigh benefits.
High cholesterol levels are a particular problem for many diabetes, and are linked strongly to an increased risk of heart disease.
The Hull study, published in the journal Diabetic Medicine, tested the theory that chemicals found in cocoa beans could influence this.
A total of 12 volunteers with the type II form of the condition were given identical chocolate bars, some enriched with polyphenols, over a 16 week period.
Those given the enriched bars experienced a small improvement in their overall cholesterol "profile", with total cholesterol falling, and levels of so-called "good" cholesterol rising.
Professor Steve Atkin, who led the study, suggested that it could mean a reduction in heart risk.
He said: "Chocolate with a high cocoa content should be included in the diet of individuals with type II diabetes as part of a sensible, balanced approach to diet and lifestyle."
However, there were some concerns from researchers at Diabetes UK that the message would be interpreted as a "green light" to eat more chocolate.
They pointed out that even bars with the highest levels of cocoa solids would contain high levels of fat and sugar, and could end up doing more harm than good.
Regular bars of two of the UK's best selling varieties of dark chocolate each contain more than 200 calories and up to 16 grams of fat.
Dr Iain Frame, director of research at leading health charity Diabetes UK, said he was unconvinced by talk of health benefits.
"On no account should people take away the message from this study, conducted in only 12 people, that eating even a small amount of dark chocolate is going to help reduce their cholesterol levels.
"The tiny health benefit of this compound found in cocoa-rich chocolate would be hugely outweighed by the fat and sugar content.
"The design of the study is also somewhat unrealistic as they asked participants to eat only around half the size of a normal, dark chocolate bar every day for eight weeks.
"It would, however, be interesting to see if further research could find a way of testing whether polyphenols could be added to foods which weren't high in sugar and saturated fat such as chocolate," Dr Frame said.