What does atrial fibrillation do to the heart?
Atrial fibrillation is a disturbance of the rhythm in the auricles of the heart (the atriums) where the muscles of the arteries contract irregularly and out of stroke with the rest of the heart. The irregular rhythm is caused by errors in the electrical signals in the atriums. When the auricles do not contract in sync with the ventricles (the chambers of the heart), it reduces the heart’s ability to pump out blood into the greater circulation, which supplies all the body’s organs. Often, the frequency of contractions in the auricles is far greater than in the ventricles in cases of atrial fibrillation. Simultaneously, the contractions are uncoordinated to a degree where the atriums do not empty the blood to the ventricles sufficiently, whereby the ventricles are not filled optimally. This results in a reduced volume of blood being sent after each heartbeat.
Cocoa reduces the risk of atrial fibrillation
Many are familiar with the fact that cocoa has several health beneficial effects – i.e. chocolate with high amounts of cocoa has such effects. The chocolate been shown to have positive cardiovascular health effects, possibly because of its high amounts of flavonoids which presumably contribute to keeping the blood vessels fully functional. Prior to this study, only limited knowledge existed about chocolate’s effect on atrial fibrillation, which affects approx. 1 million brits. Atrial fibrillation is associated with other serious conditions, herein apoplexy, heart failure, dementia and death.
The new study, led by researchers from BIDMC, Harvard T.H. Chan School of Public Health, Aalborg University and the institute of epidemiological cancer research in Denmark, is based on collected and analysed data from Danish men and women. A group of more than 55,000 Danes have agreed to share their data and participate in the study called ‘Diet, Cancer and Health’, which initially began back in 1993. The data contains detailed information about diet, lifestyle and biological material, herein blood samples, urine samples, tissue samples etc. from each study subject. In the study about the connection between chocolate intake and the development of atrial fibrillation, the researchers focused on data about the study subjects’ BMI, blood pressure, blood cholesterol, diet and lifestyle as well as conditions such as elevated blood pressure, diabetes and cardiovascular diseases and their daily chocolate intake.
Among the approx. 55,000 study subjects, 3,346 developed atrial fibrillation during the 13.5 years in which the subjects were followed. Compared to those, who consumed 1 portion of chocolate or less each month, the study subjects who consumed 1-3 portions each month, had a 10 % less risk of developing atrial fibrillation. The risk was 17 % less in those who consumed 1 portion per week, and it was 20 % less in those, who consumed 2-6 portions per week. More than 6 portions caused the effect to decrease as those, who consumed at least 1 portion per week, had 16 % less risk of atrial fibrillation, compared to those, who consumed no more than 1 portion each month. These results were non-related to gender.
One of the researchers from the study, Elisabeth Mostofsky, has stated that despite most of the chocolate, which was eaten by the study subjects, did not contain high amounts of cocoa and thus not a very high dose of the mentioned health beneficial substances, they could still observe a significant connection between chocolate consumption and a reduced risk of atrial fibrillation. This suggests that even limited chocolate intakes can have positive effects on our health. However, she points out that too much chocolate is not recommended as the excessive energy intake causes overweight and other metabolic diseases. Instead, she recommends a moderate chocolate intake with a high concentration of cocoa as this can be health-enhancing. This study can therefore contribute to the increasing amount of data, which suggests that small portions of dark chocolate as part of a balanced and healthy diet can reduce the risk of developing cardiovascular diseases.
Why does chocolate have this effect?
Earlier studies have shown that flavonoids, which the cocoa bean possesses in great amounts, seem to be a central substance in association with the positive health benefits of a chocolate intake. It has shown that a regular moderate intake is related to reduced blood pressure and reduced amounts of LDL-particles (the ‘mean’ fat) and a higher content of HDL (the ‘good’ fat) in the blood, less insulin resistance and increased blood circulation. Moreover, animal experiments have shown that flavonoids affect the cell by limiting a swelling of the so-called ‘mitochondria’ in the cell, which oversees the production of energy, and by helping the cell avoid cell death. Animal experiments have also shown that subjects, consuming foods with flavonoids, experienced less brain damage in cases of a blood clot in a heart vessel than subjects, who did not consume foods with flavonoids. Flavonoids appear to strengthen the brain cells’ ability to survive difficult situations with a limited oxygen supply, and this may explain the connection we see between chocolate intake and reduced risks of heart diseases.
