Does dark chocolate really cut diabetes risk? Some sweet news for choco lovers

If you’ve long assumed you must deprive yourself of delicious foods in order to be healthy, a new study published in the British Medical Journal offers encouraging news — eating dark

chocolate

may reduce the risk of Type 2 diabetes.
The research did not prove that the chocolate itself was responsible. It could be something else about the people who ate dark chocolate that made them less likely to develop diabetes. Dark chocolate should not be considered a “magic bullet” for preventing diabetes, said

Dr Qi Sun

, an associate professor of nutrition and epidemiology at the Harvard T H Chan School of Public Health, and the lead investigator of the study.
But the findings do build on a larger body of research demonstrating links between consuming dark chocolate and reduced risks of health conditions like high blood pressure, cardiovascular disease and insulin resistance. The results,

Dr Sun

added, suggest that a little dark chocolate can be part of a healthy diet.

What did the study find?
In the mid-1980s and early 1990s, researchers began studying three groups of predominantly white health professionals. Every four years, more than 1,90,000 participants completed detailed diet questionnaires asking how often they consumed chocolate. Beginning in 2006 and 2007, the researchers tweaked the questions to ask how often they ate dark chocolate and milk chocolate, following their health for up to 34 years. During that time, nearly 19,000 participants developed Type 2 diabetes. After adjusting for other lifestyle aspects such as exercise, alcohol consumption, smoking and how healthy their overall diets were (as well as age and family history of diabetes), the researchers found people who consumed at least five servings of any type of chocolate per week had a 10% lower Type 2 diabetes risk than those who rarely or never ate chocolate.

But when they drilled down into the data on the types of chocolates consumed, they found those who had at least five servings of dark chocolate per week had a 21% lower Type 2 diabetes risk than those who had dark chocolate less than once a month. Also, those who had milk chocolate were not protected from Type 2 diabetes but were more likely to gain weight.

What were the study’s limitations?
While the study was large and well-designed, it could not prove cause and effect, said Dr

Susan Spratt

, professor at the Duke University School of Medicine who was not involved with the study. Perhaps the people who consumed dark chocolate were healthier in other ways, she said. Maybe they exercised more, followed a healthier diet or could more easily visit a doctor when they needed to. The study group was also mostly white and well-educated, so the results may not apply to everyone, Dr Sun and his coauthors noted.
The researchers accounted for diet, lifestyle, education and wealth in their analysis, Dr Sun said. But proving that eating dark chocolate prevented Type 2 diabetes would require a clinical trial on a large group of people, giving half dark chocolate and the other half milk chocolate, and following them for decades. Such a trial would be expensive — and it would be unrealistic to devote that many years and resources to investigating a single food’s link to chronic disease, Dr Spratt said. This is why nutrition scientists often use observational studies such as this one to examine the relationship between diet and health.
What might explain the result?
Dark and milk chocolate are similar in calories, sugars and saturated fats, Dr Sun said. But dark chocolate typically contains more cocoa, which may be key to its health benefits, he and his colleagues said.
Cocoa is a bean extract rich in fibre and beneficial plant-based compounds called flavonoids, said Dr

Dariush Mozaffarian

, a cardiologist and director of the

Food is Medicine Institute at Tufts University

, who was not involved with the study. Some research suggests that flavonoids have antioxidant and anti-inflammatory effects and might help open blood vessels, which may explain cocoa’s health benefits, he said.
Some small, short-term clinical trials have suggested that dark chocolate or cocoa can reduce blood pressure and improve insulin sensitivity and insulin resistance — both of which influence the risk of Type 2 diabetes, Dr Mozaffarian said. But not all of those studies have found benefits, and some used concentrated cocoa supplements, which contain more flavonoids than a typical bar of dark chocolate.
What is the takeaway?
Dr Mozaffarian fully embraces dark chocolate as part of a healthy diet, though he says it is best to choose a variety with at least 70% cocoa. An even better option is nuts coated with dark chocolate as nuts have phytonutrients, healthy fats and fibre, he said. In recent studies, researchers have found concerning levels of lead and cadmium in dark chocolate. More research is needed to understand this potential health risk, Dr Sun said. However, those studies have suggested that consuming up to about an ounce (around 30gms) of dark chocolate per day — about a third of a regular-size Ghirardelli dark chocolate bar — is safe for most adults.
But even if it turns out that dark chocolate does protect against Type 2 diabetes, it would not be at the top of Dr Spratt’s list of ways to prevent the condition. She emphasises on a diet rich in vegetables and whole grains; avoiding processed and red meats; maintaining a healthy weight; and getting at least 150 minutes of moderate-intensity physical activity per week.
In a study published in 2023, Dr Mozaffarian and his colleagues estimated that about 70% of new Type 2 diabetes cases worldwide could be linked to poor diet. Dr Mozaffarian said it’s also helpful to limit added sugars and refined carbohydrates. But if you enjoy dark chocolate, it is OK to include it in your diet. “People think healthy eating means eating things that don’t taste good. But many delicious foods are also healthy and dark chocolate is a great example of that,” he said.
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