Eating a few pieces of dark chocolate five times a week while avoiding milk chocolate has been linked to a reduced risk of Type 2 diabetes.

The connection between chocolate consumption and Type 2 diabetes risk is "controversial," according to researchers, although they highlight that most previous studies did not explore the difference between types of chocolate.

These subtypes – dark, milk and white – have varying levels of cocoa, sugar and milk, which "may influence the association with risk of Type 2 diabetes," they added.

For the study, the team used data from three long-term studies of nurses and health care workers in the U.S.

The analysis of food frequency questionnaires taken every four years examined the link between Type 2 diabetes and total chocolate consumption in 192,028 people and chocolate type – dark or milk – in 111,654 people.

The average monitoring period was 25 years.

In the group whose total chocolate intake was analyzed, some 18,862 people developed Type 2 diabetes, which happens when the body does not use insulin properly, resulting in high blood sugar.

Researchers found those who were eating a 1 ounce serving, or 28.3 grams, at least five times a week, were 10% less likely to develop the condition compared with those who never or rarely ate chocolate.

Some 4,771 people developed Type 2 diabetes in the group analyzed by chocolate type.

The risk of the condition among the people who ate one serving of dark chocolate five times a week was 21% lower, the study found.

However, an increased intake of milk chocolate, but not dark, was associated with long-term weight gain.

Researchers said further trials are needed to confirm the findings, which have been published in The BMJ.

Diabetes U.K. estimates that about 4.4 million people in the U.K. are living with a diabetes diagnosis.

The charity also claims an additional 1.2 million people could have undiagnosed Type 2 diabetes.

As of 2022, about 830 million people globally have diabetes, according to the World Health Organisation (WHO).

Dr. Lucy Chambers, head of research communications at Diabetes U.K., said: "This research adds to the body of evidence that is being built around specific foods and their relation to risk of Type 2 diabetes, but it doesn't demonstrate that eating dark chocolate directly lowers Type 2 diabetes risk. Studying diet is complex and affected by many different interacting factors.

"Eating more dark chocolate might sound appealing, but, while it can be enjoyed in moderation, we wouldn't recommend it as a strategy for reducing your risk of type 2 diabetes based on current evidence.

"The strongest evidence for reducing Type 2 diabetes risk lies in supporting people with combined interventions, including a balanced diet, physical activity and sustained weight loss, which can be effective in reducing the risk of Type 2 diabetes by about 50% in some people."