Eating chocolate may reduce men's chance of having a stroke, a new study suggests. The study included more than 37,000 men. At the beginning of the study, they answered questions about what they ate. In the next 10 years, about 2,000 men had a first stroke. Those who ate the most chocolate had a 17% lower risk of stroke than those who ate none. The amount eaten by the top group was equal to about one-third cup of chocolate chips per week. In Sweden, where the study was done, about 90% of the chocolate eaten is milk chocolate, study authors said. The same researchers also found similar results by combining results from 5 prior studies on chocolate and stroke. Those studies included a total of 4,200 strokes. People who ate the most chocolate had a 19% lower risk of stroke than those who never ate chocolate. The journal Neurology published the study. HealthDay News wrote about it August 29.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Every now and then we hear of a study with some surprisingly good news: Chocolate is good for your health. That time has come again.

The new study on chocolate appears in the medical journal Neurology. Researchers studied more than 37,000 men. They answered questions about diet, including how much chocolate they ate. In the next 10 years, nearly 2,000 men had strokes. Here's what the study found:

• Stroke risk was lowest in those eating the most chocolate.
• The risk was 17% lower for men who ate the most chocolate than for those who ate no chocolate.
• Men who ate the most chocolate consumed about 63 grams each week. That's equal to one-third of a cup of chocolate chips.

These researchers also combined data from prior studies about chocolate and stroke risk. This technique is called meta-analysis. The combined studies showed a similar risk reduction: People who ate the most chocolate had a 19% lower stroke risk than those who ate none.

Why should this be? For years, researchers have suggested that flavonoids in chocolate lower the risk of heart attack. Flavonoids are antioxidants. These natural "scavengers" remove potentially harmful toxins from the blood. They also thin the blood a bit and reduce inflammation. Both of these effects can lower heart attack risk. But no one really knows whether it's the flavonoids in chocolate that provide its protective effect.

In fact, no one really knows if chocolate truly lowers stroke and heart attack risk (despite the findings of this and prior studies). Why?

• Some factor other than chocolate could account for the reduced risk. For example, people who like chocolate might tend to smoke less and exercise more than others. This study tried to account for such factors, but it's nearly impossible to account for them all.
• The researchers used questionnaires about diet, including chocolate. People's memory (and honesty) about what they ate may not be reliable.
• The researchers used hospital discharge records to establish the diagnosis of stroke. This means that men who had a stroke and died before being admitted to the hospital were not included. Including these men could have changed the results.
• Even if people who eat the most chocolate truly have a lower risk of stroke, other risks (such as weight gain or diabetes) may offset this benefit.
• This study included men ages 49 to 75. It lasted 10 years. A longer-term study that included younger or older adults might have come to different conclusions.

For these reasons, this study is unlikely to be the last word on whether chocolate can reduce your risk of stroke. Still, it's an appealing idea.

What Changes Can I Make Now?

Learn about the factors that increase the risk of stroke. You can make these changes now to reduce your risk:

• Diabetes -- If you have diabetes, work with your doctors to keep your blood sugar well controlled.
• A "bad" lipid profile -- If your LDL or total cholesterol is high or if your HDL cholesterol is low, work with your doctor to improve them. A combination of diet, exercise and medicines may be required.
• High blood pressure (hypertension) -- If your blood pressure runs high, reduce your intake of sodium (mostly from salt) and lose excess weight. If blood pressure stays high, your doctor may prescribe one or more medicines.
• Atrial fibrillation -- This abnormal heart rhythm may allow blood clots to form in the heart. If a clot travels to the brain, it can cause a stroke. Keeping the heart in a regular rhythm may lower your risk of stroke. Some people also take a blood thinner, such as warfarin (Coumadin).
• Carotid artery narrowing -- The carotid arteries are in the neck. They carry blood to the brain. Narrowing of these arteries from deposits of cholesterol can lead to stroke. Surgery can open them up and lower stroke risk.
• Smoking -- Commit to kicking the habit. If you have trouble quitting on your own, talk to your doctor about smoking cessation programs.

What Can I Expect Looking to the Future?

High-calorie, high-fat treats don't often turn out to be good for you. That's not likely to change. You're unlikely to hear that french fries, cheesecake or donuts provide major health benefits. But chocolate seems to be different. Perhaps it's the flavonoids. We'll need more research to be sure.

I'm sure we'll learn more about the health impact of eating chocolate. If other studies confirm that chocolate lowers stroke risk, we'll need to know the ideal "dose" and whether the type of chocolate matters. Dark chocolate is often considered the healthiest. But in Sweden, where this study was done, 90% of the chocolate eaten is milk chocolate (according to the study's authors).

It's intriguing -- and disconcerting -- when studies find health benefits from foods we thought were unhealthy choices. Perhaps other dietary villains will turn out to be health heroes. I certainly hope so.