“Our research indicates that not all chocolate is the same,” said Binkai Liu, the lead author and a doctoral student in the Department of Nutrition. “For chocolate lovers, this reminds them that small choices, such as dark chocolate instead of milk chocolate, can positively impact their health.”

The existing research on chocolate and T2D shows inconsistent findings, with few studies differentiating between chocolate types, specifically dark and milk chocolate.

The researchers aimed to address a gap in knowledge by utilizing data from the Nurses’ Health Studies I and II, as well as the Health Professionals Follow-up Study. Over more than 30 years, 192,000 adult participants who were free of diabetes at the beginning of the study reported their dietary habits, including chocolate consumption, alongside updates on their diabetes status and body weight. By the end of the study, nearly 19,000 participants had reported a diagnosis of type 2 diabetes (T2D). Among the almost 112,000 participants who specifically reported their intake of dark and milk chocolate, around 5,000 were diagnosed with T2D.

The study found that participants who consumed at least five ounces of any type of chocolate per week had a 10% lower risk of developing type 2 diabetes (T2D) than those who never or rarely consumed chocolate. Dark chocolate had an even more significant impact: participants who ate at least five servings of dark chocolate each week showed a 21% lower risk of T2D. Additionally, the researchers observed a 3% reduction in risk for every serving of dark chocolate consumed weekly. In contrast, consumption of milk chocolate was not linked to a reduced risk of T2D. Moreover, increased intake of milk chocolate—unlike dark chocolate—was associated with long-term weight gain, which can contribute to the development of T2D.

“We were surprised to find a clear distinction between the effects of dark and milk chocolate on diabetes risk and long-term weight management,” said Qi Sun, the corresponding author and an associate professor in the Departments of Nutrition and Epidemiology. “Although dark and milk chocolate contain similar levels of calories and saturated fat, it seems that the rich polyphenols in dark chocolate may counteract the negative effects of saturated fat and sugar on weight gain and diabetes. This intriguing difference warrants further exploration.”