Consumption of at least five servings of dark chocolate a week (one serving is equal to a standard chocolate bar/pack or 1 oz) compared with rare consumption was significantly associated with lower risk of type 2 diabetes in a long-term U.S. study; increased consumption of milk chocolate, however, was associated with increased weight gain.
Intake of dark chocolate instead of milk chocolate may be associated with a lower risk of type 2 diabetes. Image credit: Sci.News.
The global prevalence of type 2 diabetes has increased noticeably over the past few decades, with an estimated 463 million people affected worldwide in 2019 and projected to increase to 700 million by 2045.
Type 2 diabetes is a multifactorial disease characterized by insulin resistance and impaired insulin secretion, which can lead to numerous severe complications such as cardiovascular disease, renal failure, and loss of vision.
A growing body of research has highlighted the importance of lifestyle factors, including healthy diets, in the prevention and management of type 2 diabetes.
Higher consumption of total dietary flavonoids, as well as specific flavonoid subclasses, has been associated with a decreased type 2 diabetes risk.
In randomized controlled trials, these flavonoids exerted antioxidant, anti-inflammatory, and vasodilatory effects that might confer cardiometabolic benefits and reduce the risk of type 2 diabetes, although data were not consistent.
Chocolate, derived from the beans of the cacao tree (Theobroma cacao), is among foods with the highest flavanol content and is a popular snack globally.
However, the association between chocolate consumption and risk of type 2 diabetes remains controversial owning to inconsistent findings in observational studies.
For the new research, Binkai Liu from the Harvard T.H. Chan School of Public Health and colleagues combined data from three long-term U.S. observational studies of female nurses and male healthcare professionals with no history of diabetes, heart disease or cancer when they were recruited.
Using food frequency questionnaires completed every four years, they analyzed associations between type 2 diabetes and total chocolate consumption for 192,208 participants, and chocolate subtype (dark and milk) consumption for 111,654 participants over an average monitoring period of 25 years.
As changes in bodyweight strongly predict risks of type 2 diabetes, they also used these food questionnaires to assess participants’ total energy intake.
In the analyses for total chocolate, 18,862 people developed type 2 diabetes. After adjusting for personal, lifestyle, and dietary risk factors, the authors found that people who ate at least five servings a week of any type of chocolate showed a significant 10% lower rate of type 2 diabetes compared with those who rarely or never ate chocolate.
In analyses by chocolate subtypes, 4,771 people developed type 2 diabetes. After adjusting for the same risk factors, people who ate at least five servings a week of dark chocolate showed a significant 21% lower risk of type 2 diabetes, but no significant associations were found for milk chocolate intake.
The researchers also found a 3% reduced risk of type 2 diabetes for each additional weekly serving of dark chocolate (a dose-response effect).
Increased consumption of milk, but not dark, chocolate was associated with long term weight gain.
Although dark chocolate has similar levels of energy and saturated fat to milk chocolate, the high levels of flavanols in dark chocolate might offset the effects of saturated fat and sugar on weight gain and the risk of other cardiometabolic diseases such as diabetes.
“Increased consumption of dark, but not milk, chocolate was associated with lower risk of type 2 diabetes,” the scientists said.
“Increased consumption of milk, but not dark, chocolate was associated with long term weight gain.”
“Further randomized controlled trials are needed to replicate these findings and further explore the mechanisms.”
The study was published this week in The BMJ.
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Binkai Liu et al. 2024. Chocolate intake and risk of type 2 diabetes: prospective cohort studies. BMJ 387: e078386; doi: 10.1136/bmj-2023-078386