Milk Chocolate or Dark? the Answer Could Affect Your Risk of Diabetes.

The Washington Post / Anahad O’Connor

13:04 JST, December 5, 2024

A large new study suggests there might be good reason to indulge in chocolate this holiday season: It found that people who regularly ate chocolate had a lower likelihood of developing Type 2 diabetes.

But the findings came with an important caveat. It was only dark chocolate that was associated with a lower risk of developing the disease, not milk chocolate. It’s not entirely clear why that is. But the researchers believe that dark chocolate offers greater metabolic benefits than milk chocolate because it contains less sugar and higher levels of plant compounds that have been shown in some studies to reduce inflammation and improve insulin sensitivity.

While many previous studies have examined the health effects of eating chocolate, the new study, which was published in the BMJ on Wednesday, is one of the few to specifically compare dark and milk chocolate. It’s also one of the largest studies on the topic to date.

The facts

– The researchers analyzed data on roughly 192,000 men and women in the United States who were followed for over 30 years. The participants were part of three different cohorts of nurses, doctors and health professionals who regularly answered questions about their diets, health, weight, physical activity, and other lifestyle habits.

– After taking into account things like age, exercise levels and other factors, the researchers found that people who ate at least five ounces of dark chocolate per week – equivalent to five servings – had a 21 percent lower risk of developing Type 2 diabetes compared with people who rarely or never ate dark chocolate. For every ounce of dark chocolate that a person consumed per week, their risk of developing diabetes fell by three percent. The researchers found that this was especially the case for men and for people who were younger than 70 years old, though it’s not entirely clear why.

– For milk chocolate, there was no apparent benefit for metabolic health. In fact, as people increased their intake of milk chocolate throughout the course of the study, their likelihood of gaining weight climbed, especially if they were already obese.

Comparing milk and dark chocolate

Both dark and milk chocolate contain high amounts of fat and, in many cases, sugar. But milk chocolate tends to have a lot more added sugar.

Dark chocolate contains a lot more cocoa – ground up cacao beans. As a result, it typically has several times the concentration of beneficial plant compounds called polyphenols, particularly one type known as flavonoids. These naturally occurring substances act as antioxidants and are found in many plant foods, including fruits, vegetables, tea and coffee. A number of studies have indicated that flavonoids might help protect against Type 2 diabetes by improving how our bodies respond to insulin and break down sugar as well as by protecting the beta cells that produce and release insulin from the pancreas.

Many studies have also suggested that flavonoids can lower the risk of heart disease and high blood pressure.

“In general, polyphenols have been demonstrated to be beneficial for diabetes biomarkers in randomized controlled trials,” said the lead author of the new study, Binkai Liu, a doctoral student in the Department of Nutrition at the Harvard T.H. Chan School of Public Health. “That’s well established.”

White chocolate contains no cocoa powder, and as a result it has little or no flavonoids or polyphenols. It also has the highest sugar content of any type of chocolate.

The limitations of the study

The authors of the new study cautioned that their findings showed only a correlation between dark chocolate and diabetes risk, not causation. It’s possible that something else could explain the findings. People who eat dark chocolate might be more health conscious than those who prefer to eat milk chocolate. The researchers did find, for example, that people who ate dark chocolate tended to eat more fruits and vegetables and generally had healthier diets.

“We can’t say for certain that eating dark chocolate will lower your risk of Type 2 diabetes,” Liu said. “We can say that eating it is associated with a lower risk. But we don’t want people to overinterpret the results.”

Liu said it’s possible that dark chocolate consumption is merely a marker of a healthier lifestyle. But even when she and her colleagues factored this into their analysis, they still found a link between dark chocolate and a lower risk of diabetes.

Simin Liu, a professor and nutrition expert at the University of California at Irvine who studies the health effects of chocolate, called the new findings promising. He said it was plausible that the flavonoids in dark chocolate might offer protection against Type 2 diabetes. But he said more rigorous research was needed to show cause and effect, and to understand whether there’s an optimal amount and frequency of dark chocolate consumption that’s necessary to produce health benefits.

What we know about chocolate and health

At least three other large studies have found that eating chocolate is associated with a reduced likelihood of developing Type 2 diabetes. Two clinical trials found that assigning people to eat dark chocolate every day for two weeks lowered their blood pressure levels, improved their insulin sensitivity, and led to greater improvements in various markers of cardiovascular and metabolic health compared with people who were assigned to eat white chocolate.

One large study assigned people to take a daily supplement containing cocoa extract every day for several years and had mixed results. It found that the cocoa supplements made people less likely to die of cardiovascular disease but did not lower their risk of developing Type 2 diabetes. The trial was funded in part by Mars Edge, the life sciences division of Mars Inc., which sells chocolate and other candy.

Liu at Harvard pointed out that that trial involved older adults who were on average 72 years old, which might explain the discrepancy. Her study found that the association between dark chocolate intake and a reduced risk of diabetes was primarily seen in people who were younger than 70 years old.

She emphasized that while dark chocolate can be a healthy snack, it’s important to not overdo it. “The key message is balance but not excess,” she added. “The important thing to prioritize in your diet is nutrient-rich foods.”

How to choose the healthiest chocolate

If you do want to consume chocolate for its potential health benefits, consider the following:

– Milk and white chocolate have fewer flavonoids and polyphenols than dark chocolate, and in many cases they also have a lot more sugar.

– You can identify dark chocolate by the percentage of cocoa solids. Dark chocolate contains at least 50 percent cocoa solids. Milk chocolate contains less than 50 percent cocoa solids, and white chocolate doesn’t contain any cocoa solids. (It contains cocoa butter, milk and sugar.) In general, the higher the content of cocoa solids, the less sugar. Liu at UC Irvine recommends choosing dark chocolate with a cocoa content of 70 percent or higher “to maximize potential benefits and minimize sugar and calorie intake.”

– A serving of chocolate is about one ounce, or roughly one square of chocolate. Some experts recommend eating no more than one or two squares daily.

– Dark chocolate contains more flavonoids than white and milk chocolate, but it can also contain higher levels of heavy metals such as lead and cadmium. That’s because these metals tend to be concentrated in the cocoa. A recent analysis by Consumer Reports found that the amount of lead and cadmium in dark chocolate products can vary widely. The group’s tests showed, for example, that dark chocolate bars such as Sam’s Choice (Walmart) Dark Chocolate 85% Cocoa and Divine 70% Deliciously Smooth Dark Chocolate were relatively low in heavy metals, while some other brands were not.

– Experts say it’s safe for people to eat dark chocolate in moderation. But heavy metals can be particularly damaging to developing brains and nervous systems, so it is probably best for pregnant people and young children to consume dark chocolate sparingly.