Dark Chocolate May Help Lower Diabetes Risk, Per New Study

If you love chocolate, you’re not alone. In 2023, Americans spent almost $26 billion on chocolate, and chocolate sales have increased 5.8% year-over-year. And while we know dark chocolate can have some health benefits for your heart and brain, it’s been less clear if eating chocolate has any link to type 2 diabetes—for better or for worse. 

After all, we know that eating too much sugar and saturated fat can be a contributing cause of diabetes, and chocolate contains both. But chocolate can also have some health benefits—especially dark chocolate.

Researchers from Harvard were also curious to know if eating chocolate has any influence on type 2 diabetes risk. So they conducted a study that was published on December 4, 2024, in The BMJ—formerly The British Medical Journal. Here’s what they found. 

How Was This Study Conducted?

Researchers pulled data from three large, long-term cohort studies that had previously collected data from a total of almost 300,000 individuals: the Nurses’ Health Study (NHS, initiated in 1976), the Nurses’ Health Study II (NHSII, initiated in 1989) and the Health Professionals Follow-up Study (HPFS, initiated in 1986). 

The years from which data were analyzed were 1986-2018 (NHS), 1991-2021 (NHSII), and 1986 to 2020 (HPFS). Participants in both the NHS and NHSII were female nurses. The HPFS was made up of male health professionals, including doctors from various specialties of medicine. After baseline data was collected, participants filled out updated questionnaires every two years.

The BMJ study was split into two parts. For the first part, researchers looked at total chocolate consumption and whether there is a link between it and the development of diabetes. For this part of the study, the analysis included data from more than 192,000 participants, all of whom were free of heart disease, cancer and type 2 diabetes when baseline data was collected. The average age across all three studies was 47 at baseline.

The second part of this study analyzed diabetes risk and chocolate consumption by type: dark, milk and white. For this analysis, more than 111,000 participants were included with an average age of 64 at baseline, taking the average across all three studies.

In the previous three studies, participants filled out food frequency questionnaires every four years. This included how often and how much chocolate they ate. In all three studies, the first few years only included general questions about chocolate consumption. It wasn’t until 2006 that questions about specific types of chocolate consumption were asked. 

While analyzing the links between chocolate consumption and diabetes, researchers considered many variables, including ones that might influence diabetes risk. This included race/ethnicity, body weight, waist circumference, smoking status, alcohol consumption, menopause status and hormone use, blood pressure, cholesterol levels, education level, physical activity and family history of diabetes. It also included overall diet quality, which was graded using the Alternate Healthy Eating Index-2010 (AHEI). A high score on the AHEI reflects a varied eating pattern consisting of lots of whole foods, like the Mediterranean diet.

Diabetes diagnoses were self-reported in the biennial follow-up questionnaires and were then confirmed with additional questionnaires asking about lab results, symptoms and treatments. 

What Did This Study Find?

After adjusting for potential lifestyle and dietary risk factors, researchers found that participants who consumed 5 or more servings per week of any chocolate showed a 10% lower relative risk of type 2 diabetes compared to those who never or rarely consumed chocolate. 

For the second analysis that was broken down according to chocolate type, researchers found that dark chocolate, but not milk chocolate or white chocolate, was associated with a reduced risk of type 2 diabetes. Specifically, people who consumed at least 5 servings of dark chocolate per week had a 21% lower rate of type 2 diabetes compared to those who never or rarely ate dark chocolate. 

Researchers went even deeper and found that those with a higher diet quality based on the AHEI scores showed even stronger associations between a minimum of 5 servings of dark chocolate per week and diabetes risk—a 34% lower risk of diabetes for those with higher diet quality compared to those with lower quality diets. 

Another finding from this analysis was that milk chocolate consumption was significantly associated with more weight gain than dark chocolate. 

How Does This Apply to Real Life?

Researchers surmise that the polyphenols (antioxidants) in dark chocolate may be responsible for its reduction in diabetes risk. Out of all the types of chocolate, dark chocolate contains the most cocoa—and cocoa is loaded with flavan-3-ols, a type of polyphenol. White chocolate, by the way, contains no cocoa and no polyphenols, and typically has the highest level of sugar out of all the chocolate types. 

Flavan-3-ols may mitigate diabetes risk, say the researchers, by improving insulin sensitivity, protecting pancreatic beta cells from oxidative stress, lowering pro-inflammatory substances, and promoting the production of substances that dilate blood vessels. Altogether, these pathways may improve glucose metabolism and reduce the risk of type 2 diabetes.

So what does this all mean? Well, first, just because dark chocolate has health benefits that milk and white chocolates don’t, does not mean you should eat unlimited amounts of it. You want to aim for a balanced, varied diet, encompassing a variety of foods. That way, you get the wide range of nutrients you need for good health and disease prevention. This study examined chocolate intake according to serving size, so if you’re eating dark chocolate every day, stick to the serving size—about 1 to 2 ounces (check the label to see how much that is). 

When you choose chocolate, make it dark—at least most of the time. One thing this study did not do was break down the percentages of cocoa in the dark chocolate and compare each of them against diabetes risk. It lumps all dark chocolate together. 

You’ll typically know a chocolate is dark based on its percentage of cocoa—that and the label will say that it’s dark chocolate. And while there seems to be no conclusive agreement on what minimal percentage of cocoa makes chocolate dark, know that the higher the percentage of cocoa, the more health benefits it’s likely to have. The darker the chocolate, the more bitter it will taste as well. 

If you’re currently a milk chocolate lover and want to become a lover of dark chocolate, start with lower cocoa percentages and work your way up over time. It’s also helpful to have additions to the chocolate to help your palate adjust—like nuts or mint flavoring. Plus, nuts add more health benefits, so it’s a win-win.

The Bottom Line

This study suggests that eating at least 5 servings of dark chocolate per week may reduce your risk of type 2 diabetes by 21%. The risk may be reduced by up to 34% if you also eat an overall healthy diet full of fiber- and antioxidant-rich foods and low in added sugar, saturated fats and highly processed foods. This finding emphasizes the importance of including a variety of nutrient-dense foods in your routine—not just dark chocolate. Other health habits that influence diabetes risk include physical activity, sleep quantity and quality and stress, so it’s important to take a holistic approach to diabetes risk reduction. 

If you’ve got a sweet tooth, a little bit of dark chocolate each day should fit easily into that approach.