Replacing snacks with a little piece of dark chocolate might help the heart, German researchers say. (Toby Talbot/Associated Press)

Eating a small amount of chocolate daily may help the heart and lower blood pressure, a European study suggests.

Nutrition researchers published their findings on 19,357 adults aged between 35 and 65 in Wednesday's issue of the European Heart Journal.

The team used questionnaires to analyze the diet and exercise habits of participants for at least 10 years.

Those who ate the most chocolate — an average of 7.5 grams per day or one square of a 100-gram bar — had lower blood pressure and a 39 per cent lower risk of having either a heart attack or stroke compared with those who ate the least chocolate, the researchers found.

If people eating the least amount of chocolate increased their intake by six grams a day, 85 fewer heart attacks and strokes per 10,000 people could be expected to occur over a period of about 10 years, said lead researcher Brian Buijsse of the German Institute of Human Nutrition.

"It's a bit too early to come up with recommendations that people should eat more chocolate, but if people replace sugar or high-fat snacks with a little piece of dark chocolate, that might help," Buijsse said.

Over eight years, 166 heart attacks (24 fatal) and 136 strokes (12 fatal) occurred, based on death certificates.

But if someone were to eat a small amount of chocolate every day without consuming fewer calories elsewhere to compensate or burning it off with exercise, then weight gain will occur, the researchers cautioned.

Antioxidant effect?

The study's authors only observed participants and did not give people chocolate directly to test its effects on the body.

The study's authors believe that flavanols in cocoa may be the reason why chocolate seems to be good for people's blood pressure and heart health. Since there is more cocoa in dark chocolate, dark chocolate may have a greater effect.

Flavanols are a class of the antioxidant flavonoids that are found in many vegetables, cocoa and red wine.

The flavanols in cocoa may be responsible for improving the availability of nitric oxide from the cells lining the inner wall of blood vessels, Buijsse said.

When the nitric oxide gas is released, blood vessels relax and widen, which may help lower blood pressure. The gas also improves the function of platelets in the blood.

A subset of findings from 1,568 participants who were asked to recall what type of chocolate was consumed in the last 24 hours showed 57 per cent ate milk chocolate, 24 per cent dark chocolate and two per cent white chocolate.

Cocoa content

Participants had no history of heart problems and their smoking and exercise habits were similar. Blood pressure, height and weight measurements were taken as part of a larger study called the European Prospective Investigation into Cancer or EPIC.

It's difficult to link the reduction in heart disease and stroke risk to the chocolate alone, since there may have been other differences between the study participants, cautioned Alice Lichtenstein, a nutritionist at Tufts University School of Medicine.

"The relationship between chocolate and good health outcomes is still uncertain," Lichtenstein said. "If somebody really enjoys eating chocolate, then they should have a small amount of that and just really enjoy it."

Basic scientific suggests dark chocolate containing at least 70 per cent cocoa content reduces oxidative stress and can improve blood flow and blood pressure, Frank Ruschitzka of Switzerland's University Hospital Zurich said in commenting on the study on behalf of the European Society of Cardiology, which publishes the journal.

The study was funded by the German government and the European Union.

With files from The Associated Press