Dark chocolate is thought to have many health benefits – from guarding against cardiovascular disease to lowering blood pressure. Now, a new study published in the British Medical Journal (BMJ) suggests eating dark chocolate could also reduce the risk of developing type 2 diabetes.
Scientists and medical professionals believe this could be significant because diabetes has become increasingly widespread since the 1990s.
According to the latest World Health Organization data on diabetes, the number of people living with type 1 or 2 diabetes around the world quadrupled to 830 million between 1990 and 2022, with the vast majority of those suffering from type 2.
The consequences of this can be significant: Diabetes can cause blindness, kidney failure, heart attacks, stroke and require lower limb amputation.
So what did this latest study reveal about dark chocolate and type 2 diabetes?
What is the difference between type 1 and type 2 diabetes?
Although type 1 and type 2 diabetes share a name, there are stark differences between how each of these chronic conditions in the body regulates blood sugar, known as glucose.
Type 1 diabetes occurs when the body’s immune system malfunctions and launches an autoimmune response against its own healthy cells. This occurs when the immune system incorrectly identifies these healthy cells as a foreign threat to the body, leading to the destruction of insulin-producing cells in the pancreas. As a result, the body loses its ability to regulate blood sugar levels effectively.
It is still unclear how type 1 diabetes develops but most research points to a combination of a genetic predisposition in the individual and environmental triggers such as certain viruses that may trigger an autoimmune response.
According to a 2023 study published by several Greek medical institutions, 8.4 million people worldwide were suffering from type 1 diabetes in 2021. By 2040, the number of people living with type 1 diabetes globally is expected to range between 13.5 million and 17.4 million.
Individuals diagnosed with type 2 diabetes experience insulin resistance, a condition that causes their bodies to continue to produce insulin but be unable to use it efficiently. This impaired insulin function prevents proper regulation of blood sugar levels.
Type 2 diabetes is a chronic condition that typically develops gradually over several years. It is strongly associated with lifestyle factors, particularly physical inactivity and obesity. While it can occur at any age, this form of diabetes is most commonly diagnosed in adults.
What did the study into dark chocolate and type 2 diabetes reveal?
Roughly 192,000 adults in the US took part in three studies over 34 years conducted by Harvard researchers – the Nurses’ Health Studies I and II and the Health Professionals Follow-up Study.
Not all subjects had type 2 diabetes at the beginning of the study. Participants reported their diabetes status (if any), eating habits, general weight and chocolate consumption over time.
Individuals who regularly consumed dark chocolate – specifically five or more servings per week – experienced a 21 percent reduction in the risk of developing type 2 diabetes. Risk was measured by comparing the incidence of type 2 diabetes among participants who consumed different amounts of chocolate.
Throughout the course of the studies, approximately 19,000 individuals who did not previously have diabetes were diagnosed with type 2 diabetes.
Among the nearly 112,000 participants who reported consuming chocolate, only 5,000 went on to develop type 2 diabetes, however.
The studies revealed that while dark chocolate had beneficial effects, other types of chocolate did not.
“Increased consumption of dark, but not milk, chocolate was associated with lower risk of T2D [type 2 diabetes]. Increased consumption of milk, but not dark, chocolate was associated with long-term weight gain,” the report on the three studies stated.
“Our findings suggest that not all chocolate is created equal,” lead researcher Binkai Liu, doctoral student in the Department of Nutrition at Harvard said in a statement.
“For anyone who loves chocolate, this is a reminder that making small choices, like choosing dark chocolate over milk chocolate, can make a positive difference to their health.”
Why is dark chocolate good for us?
Dark chocolate has been found to offer several health benefits, largely due to its rich concentration of flavonoids, especially flavanols. These are powerful antioxidants found in cocoa solids and are key to understanding the scientific basis of dark chocolate’s positive health effects.
According to research, the flavanols in dark chocolate help improve cardiovascular health by enhancing blood flow and reducing blood pressure.
“Chocolate contains high levels of flavanols, which promote cardiometabolic health and reduce the risk of type 2 diabetes (T2D), as shown in randomised controlled trials,” the studies’ report found.
Additionally, these compounds have been shown to lower LDL cholesterol levels while increasing HDL cholesterol, promoting a healthier lipid profile.
HDL, known as “good cholesterol”, collects excess cholesterol from the bloodstream and tissues, while LDL, known as “bad cholesterol” can build up in artery walls, forming plaque which narrows and stiffens arteries. In some cases, this can lead to atherosclerosis, the hardening of the arteries, which can lead to coronary artery disease, heart attack, stroke, and poor blood circulation in the limbs.
Dark chocolate’s antioxidant properties also play a role in combating oxidative stress and inflammation in the body. This can potentially reduce the risk of chronic diseases and support overall cellular health. Furthermore, research suggests that the flavanols in dark chocolate may enhance cognitive function and mood, possibly due to their effect on cerebral blood flow and neurotransmitter activity.
“Higher consumption of total dietary flavonoids, as well as specific flavonoid subclasses, has been associated with a decreased risk of T2D [type 2 diabetes]. In randomised controlled trials, these flavonoids exerted antioxidant, anti-inflammatory, and vasodilatory effects that might confer cardiometabolic benefits and reduce the risk of T2D [type 2 diabetes],” the authors of the report wrote.
Dark chocolate also has a high concentration of minerals such as iron, magnesium and zinc, further enhancing its nutritional value. Research suggests these minerals support various bodily functions, from oxygen transport to enzyme activity and immune system regulation.
Health benefits are most pronounced in dark chocolate with a high percentage of cocoa solids – typically 70 percent or more. As cocoa content increases, so does the concentration of beneficial compounds, while higher sugar content generally decreases them.
“Even though dark and milk chocolate have similar levels of calories and saturated fat, it appears that the rich polyphenols in dark chocolate might offset the effects of saturated fat and sugar on weight gain and diabetes. It’s an intriguing difference that’s worth exploring more,” said report author Qi Sun, associate professor in the Departments of Nutrition and Epidemiology, in a statement.
What else can reduce the risk of developing type 2 diabetes?
In a study in Brazil this year, researchers from the Department of Internal Medicine in the State University of Rio de Janeiro and Lagoa Federal Hospital of Rio de Janeiro found that sticking to a plant-based diet not only lowers the risk of developing type 2 diabetes but also reduces our carbon footprint.
“A plant-based diet may be important not only to prevent T2DM [Type 2 Diabetes Mellitus – the scientific name for diabetes] and obesity and to improve other cardiovascular risk factors (high blood pressure and dyslipidemia), but also to ease the impact on the environment,” the authors of the study said. “A sustainable diet in which animal-based products, especially red meat and milk/dairy products, are replaced by plant-based products, has the potential to reduce greenhouse gas emissions.”
In general, according to research, a diet focused on fibre-rich foods such as fruit, vegetables, nuts, seeds and whole grains can help reduce the risk of developing type 2 diabetes.
A 2020 study coordinated by the Medical Research Council Epidemiology Unit at the University of Cambridge found that consuming a diet abundant in fruit and vegetables could reduce the risk of developing type 2 diabetes by as much as 50 percent.
“This study suggests that even a modest increase in fruit and vegetable intake could help to prevent type 2 diabetes, indicated by objective biomarkers of consumption, regardless of whether the increase is among people with initially low or high intake,” stated the authors.
